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The use of strong brine and HCl solutions to process nickel sulfide concentrates Malkhuuz, Ganbold 2006

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T H E USE OF STRONG BRINE AND H C 1 SOLUTIONS TO PROCESS NICKEL SULFIDE CONCENTRATES  by GANBOLD M A L K H U U Z  B . S c , Colorado School of Mines, 2000  A THESIS S U B M I T T E D IN P A R T I A L F U L F I L L M E N T O F T H E R E Q U I R E M E N T F O R T H E D E G R E E OF  MASTER'OF APPLIED SCIENCE in  THE F A C U L T Y OF G R A D U A T E STUDIES  Materials Engineering  T H E UNIVERSITY OF BRITISH C O L U M B I A October 2 0 0 6 © Ganbold Malkhuuz, 2 0 0 6  ABSTRACT  The mixture o f hydrochloric acid and magnesium chloride is a good lixiviant for the processing o f sulfide minerals, concentrates and matte samples. The proton activity in this mixture deviates positively from ideal activity. This enhances the leaching power to break sulfide lattices down and to dissolve metals into solution. Magnesium (chloride) was chosen because it is one o f a few reusable salts among alkali and alkali earth metal chlorides. The thermodynamic  properties  o f this mixture are best characterized by activity  coefficients o f contributing ions i n solution. The activity coefficient o f hydrochloric acid in this mixture was measured at a total ionic strength o f two at temperatures o f 25, 35, and 45°C applying the Electro Motive Force ( E M F ) measurement  method. Further measurements at higher  temperatures and higher ionic strengths were complicated due to unstable readings o f the potentials. Therefore, a mathematical method published by Meissner was utilized to calculate the activity coefficients o f hydrochloric acid and magnesium chloride i n a mixture. Based on these calculations, individual ion activities were assigned using Bates' equation and Jansz's approach o f applying variable water activities, hydration numbers and osmotic coefficients. Based on the individual ion activity, p H values were estimated for solutions where measurements were not applicable. A s part o f the thermodynamic studies o f this mixture, the solubility limit o f MgCl2 i n hydrochloric acid solutions was investigated. The solubility o f M g C l 485.6 g/1 at 22°C and 557 g/1 at 82.5°C. The solubility o f M g C l  2  i n water was measured as i n 6m HC1 solutions was  2  measured as 243 g/1 at 22°C and 452 g/1 at 82.5°C. Furthermore, the leaching chemistry o f individual sulfide minerals-pyrite, millerite, troilite, heazelwoodite, violarite, and chalcopyrite were investigated in M g C l - H C l solutions. Pyrite was 2  the most refractory mineral. About 6% iron was extracted i n the mixture o f 2m M g C l and 3-10m 2  of HC1 at 60°C. Over 90% o f iron was extracted from troilite i n the mixture o f 2m MgCl2 and 3m HC1. Millerite dissolved at acid concentrations greater than 6m HC1. A t 60°C, 60% o f nickel was extracted in the mixture o f 2m M g C l and 10m HC1. The dissolution results o f these minerals were 2  consistent with the thermodynamic predictions. About 20% o f the nickel from violarite was extracted i n mixtures with l - 6 m HC1. The nickel extractions were increased up to 30% i n mixtures of 10m HC1. About 60% o f the heazelwoodite was dissolved i n the mixture o f 2m M g C l and l m 2  HC1. The heazelwoodite dissolution was consistent with the thermodynamic predictions described in section 2.2.6. In all above cases, the leaching time was 24 hours. Chalcopyrite partially leached (-22%) i n the mixtures with 7m HC1 at 100°C. It dissolved forming cupric chloride, ferric  ii  chloride and the hydrogen sulfide gas ( R X N 4.4 i n section 4.4.3). N o phase transformation (copper enriched product such as covellite) was observed. The results o f individual mineral leaching experiments suggested the possibilities and conditions to process commercial sulfide products i n this mixture. T w o sulfide concentrates and a matte sample supplied by B H P Billiton were studied. L o w M g O concentrate that consists o f mainly pentlandite and pyrrhotite yielded 95% N i , 87% Fe, 81%> C o and 58%> C u extractions i n solutions o f 8m HC1 and 2m M g C ^ with a retention time o f 2 hours. The solid residue in this case contained mainly pyrite, talc and quartz. The high M g O concentrate that consists o f mainly pentlandite yielded 95% N i , 84% Fe, 75% C o and 19% C u extractions in the mixtures o f 6m HC1 and 2m M g C L . at 100°C. The leach time was one hour. The leach residue i n this case contained mostly quartz and talc. The addition o f 0.5m cupric or ferric chloride to leach solutions o f low M g O concentrate did not improve metal extractions due to the formation o f copper and sulfur enriched layers on the particle surface. The reason is explained by the strong tendency o f cupric or ferric ions to react with product gases such as H2S and H forming copper sulfide or elemental sulfur, respectively. 2  The additions o f either cupric or ferric chlorides to leach solutions o f high M g O concentrate leaching also retarded metal dissolution. The reason o f this low metal recovery is believed to be a formation o f sulfur and oxidized layers on the surface o f the particles. This low metal extraction is also explained by the same phenomenon as above in the case o f ferric addition. The pentlandite, which is the main composition o f the feed, remained substantially unleached. N i c k e l matte that mainly consisted o f heazelwoodite yielded over 99% metal extractions i n 6m acid solutions; however, the same metal extractions were obtained i n 3m HC1 mixtures with the exception o f copper. The leach residue, where the highest metal extractions were obtained, consisted o f 60% suredaite (a mixture o f arsenic, sulfur and copper) i n addition to 20% sulfur, according to the X R D and S E M - E D X . L o w copper extraction from this sample was caused by the strong tendency o f cupric ion to precipitate i n the presence gases from heazelwoodite dissolution.  iii  TABLE OF CONTENTS  ABSTRACT  ii  T A B L E OF CONTENTS  iv  LIST O F T A B L E S  vii  LIST O F F I G U R E S  ix  CHAPTER 1 INTRODUCTION  1  CHAPTER 2 LITERATURE REVIEW  3  2.1 Nickel-cobalt production 3 2.1.1 General.:..: •. 3 2.1.2 Processing Options 3 2.1.2.1 Sulfide Processing 4 2.1.2.2 Laterite Processing 5 2.1.3 Processes and Plant Practices.... 6 2.1.3.1 A m m o n i a Pressure Leach: The Sherritt Gordon Process 6 2.1.3.2 Ammonia-Ammonium Carbonate Atmospheric Leach: The Queensland N i c k e l Laterite Treatment Plant [87] 7 2.1.3.3 Total Pressure Oxidation P L A T S O L Process [84] 8 2.1.3.4 The Activox Process at Tati N i c k e l M i n e in Botswana 10 2.1.3.5 Additional Processes for Sulfide Concentrates 11 2.1.3.6 H i g h Pressure A c i d Leaching: M o a B a y Project 12 2.1.3.7 Cawse Project 13 2.1.3.8 Bulong Project 14 2.1.3.9 MurrinMurrin ...15 2.1.3.10 Inco Laterite Process 16 2.1.3.11 Chloride Leach Process: Falconbridge Refinery 17 2.1.3.12 Atmospheric A c i d Chloride Leach ( A A L ) Process: Sechol Project 19 2.1.4 Technology Summary: Shortcomings o f the Existing Technologies 21 2.1.5 W h y M g C b ? Uniqueness o f this mixture 22 ;  2.2 Thermodynamics o f aqueous chloride media 2.2.1 General 2.2.2 Fundamental expressions o f aqueous chloride media 2.2.3 Estimation o f activity coefficients i n aqueous chloride media 2.2.3.1 Estimation methods o f activity coefficients i n aqueous chloride media 2.2.3.2 Estimating activity coefficients by Meissner method 2.2.3.3 Experimental methods to estimate activity coefficients: E M F measurement 2.2.4 Corresponding water activity or osmotic coefficient 2.2.4.1 Expressions for water activity and osmotic coefficient 2.2.4.2 Estimating osmotic coefficients o f HC1 and M g C l 2 2.2.5 Individual ionic activities 2.2.5.1 Individual ionic activities i n single/mixed electrolytes 2.2.5.2 Estimation o f individual ionic activities and p H o f a mixture 2.2.6 Thermodynamic predictions 2.2.7 Chloride complexes  24 24 25 26 26 29 32 34 34 35 36 36 39 44 47  iv  2.2.8 Solubility o f chloride salts 2.2.9 Effect o f A1C1 , N a C l and C a C l on activities o f M g C l + H C l mixture 2.2.10 Summary o f thermodynamic review 3  2  50 51 54  2  CHAPTER 3 EXPERIMENTAL ASPECTS  56  3.1  Experimental procedures and methods  56  3.2  Experimental instruments and set-up  57  3.3  Chemicals, minerals and concentrate samples  59  3.4  Solution preparation.  61  3.5  The basic principles o f the S E M - E D X , X R D analyses  62  C H A P T E R 4 R E S U L T S A N D DISCUSSIONS  64  4.1 Thermodynamic measurement 64 4.1.1 E M F measurement o f the cell M g C l - H C l - H 0 using P t / H - A g / A g C l electrodes with no junction 64 4.1.2 Solubility o f M g C i i n water and HC1 solutions. 67 4.1.3 Summary o f the thermodynamic measurements 68 2  2  2  2  4.2 Individual mineral leaching 4.2.1 Pyrite(P) 4.2.2 Millerite ( M ) 4.2.3 Violarite (V) 4.2.4 Troilite (T) 4.2.5 Heazelwoodite (H) 4.2.6 Chalcopyrite (C) 4.2.7 Summary o f individual mineral leaching  69 69 70 72 74 75 77 78  4.3 Commercial concentrates and matte leaching 4.3.1 L o w M g O concentrate 4.3.2 H i g h M g O concentrate 4.3.3 N i c k e l matte  79 79 81 84  4.4 X R D , S E M - E D X analyses 4.4.1 Pyrite and leach residue 4.4.2 Millerite and leach residue 4.4.3 Violarite and leach residue 4.4.4 Chalcopyrite and leach residue 4.4.5 L o w M g O concentrate and its leach residue 4.4.6 H i g h M g O concentrate and its leach residue 4.4.7 N i c k e l matte and its leach residue  87 87 89 90 91 93 97 103  4.5  105  Summary o f commercial concentrates leaching and X R D , S E M analyses  C H A P T E R 5 CONCLUSIONS AND RECCOMMENDATIONS  107  5.1  Conclusions  107  5.2  Recommendations  108  References  109  V  Appendix 1  Certificates of analysis  116  Appendix 2  Summary of thermodynamic calculations  126  Appendix 3  Experimental aspects: Procedures and methods  135  Appendix 4  Mass balances of selected tests  144  vi  LIST O F T A B L E S  Table 2.1  Laterite Processing Plants based on the Caron process [1, 2,13]  5  Table 2. 2  Laterite Processing Plants based on H P A L [1, 2,13]  6  Table 2. 3  Hydration numbers of some simple salts and ions [28]  37  Table 2. 4  Hydration number at infinite dilution (ho) and (3 values [7]  38  Table 2. 5  Calculated hydrogen ion activity based on individual ion calculations  40  Table 2. 6  Comparison of p H values based on the two different approaches  40  Table 2. 7  Estimated p H of solution mixtures at temperatures  41  Table 2. 8  Calculated individual ionic activity coefficients for HC1 in relation to molal concentration and temperature  Table 2. 9  42  Calculated individual ionic activity coefficients for M g C h in relation to molal concentration and temperature  Table 2.10  42  Calculated individual ion activity coefficients for a mixture of HCI-MgCh in relation to molal concentrations of each species at 2 5 ° C  Table 2.11  43  The A G and estimated p H values for the dissolution of selected sulfide 0  minerals  44  Table 2.12  Strengths of chloro-complexes according to periodicity [28]  47  Table 2.13  Resume of the common chloro-complexes [6]  48  Table 2.14  A G reaction of selected chloride complexes at 2 5 ° C , kJ/mole  50  Table 2.15  Effect of added salts on calculated HC1 activities at 2 5 ° C  52  Table 3.1  Summary of mineral and concentrate samples  60  Table 3. 2  Solution preparation example for the E M F measurement  61  Table 3. 3  Solution preparation example for leaching tests  61  Table 4.1  Solution compositions, measured and corrected E M F , calculated activity  0  coefficients for HC1 at 25°C  64  Table 4. 2  Harned equation coefficients  65  Table 4. 3  Summary of M g C h solubility [g/1] in acid solutions  67  Table 4.4  Assays and mineralogical compositions of millerite sample  70  Table 4. 5  Dissolution of metals from millerite leaching at 6 0 ° C  71  Table 4. 6  Assays and mineralogical compositions of violarite sample  72  vii  Table 4. 7  Ni & Fe extractions from violarite sample at 60 C  73  Table 4. 8  Assays and mineralogical compositions of troilite sample  74  Table 4.9  Assay of heazelwoodite sample, %  75  Table 4.10  Summary of heazelwoodite leaching at 6 0 ° C  76  Table 4.11  Assays and mineralogical compositions of chalcopyrite sample  77  Table 4.12  Summary results of chalcopyrite dissolution  77  Table 4.13  Metal extractions from matte sample at 6 0 ° C  86  Table 4.14  Metal extractions from matte sample at 100°C  86  Table 4.15  Composition of pyrite leach residue (10m HCl-2m MgCI at 60°C)  Table 4.16  Detailed mineral assay of low M g O concentrate (supplied from B H P Billiton)..  88  2  93 Table 4.17  Contents of low M g O concentrate residue (8m HCl-2m MgCl )  95  Table 4.18  Contents of low M g O concentrate leach residue (6m HCl-0.5m MgCl2-0.5m  2  CuCl atl00°C)  97  2  Table 4.19  Compositions of high M g O concentrate leach residues (6m HCl-2m M g C l at 2  100°C) Table 4. 20  99  Compositions of high M g O concentrate leach residue (6m HCl-2m M g C l 2  0.05m C u C l a t 100°C)  101  2  Table 4. 21  Compositions of high M g O concentrate leach residue: (6m HCl-2m M g C l 2  0.2m C u C l at 100°C)  102  2  Table 4. 22  Compositions of high M g O concentrate leach residue: (6m HCl-2m M g C l 2  0.2m F e C l at 100°C)  103  Matte leaching solid residue compositions  105  3  Table 4. 23  viii  LIST O F F I G U R E S Figure 2.1  Ammonia-Ammonium Carbonate Atmospheric Leach Flowsheet [87]  8  Figure 2. 2  Proposed P L A T S O L flowsheet for C u - N i - C o - P G M sulfide concentrates from NorthMet Mine [84]  9  Figure 2. 3  The Activox Process Flowsheet at Tati Nickel Mine [85]  10  Figure 2. 4  Pressure Acid Leaching Moa Bay Flowsheet [14]  12  Figure 2. 5  High Pressure Acid Leaching Cawse Flowsheet [87]  14  Figure 2. 6  High Pressure Acid Leaching Bulong Flowsheet [87]  15  Figure 2. 7  High Pressure Acid Leaching Murrin Murrin Flowsheet [87]  16  Figure 2. 8  High Pressure Acid Leaching Goro Flowsheet [87]  17  Figure 2. 9  Falconbridge Chloride Leaching Refinery Flowsheet [13]  18  Figure 2.10  Sechol Flowsheet for Laterite Treatment at Atmospheric Pressure [11,12] ...20  Figure 2.11  Calculated y ci of a mixture having I compared with experimental data H  from E M F measurement at temperatures [43] Figure 2.12  31  Calculated activity coefficient vs. reference data [42] at 2 5 ° C for single electrolytes  Figure 2.13  35  Calculated osmotic coefficients vs. reference data [42] at 2 5 ° C for single electolytes  36  Figure 2.14  Predicted p H for the dissolution of selected minerals  45  Figure 2.15  Eh-Iog[Cl] diagram at 2 5 ° C [28]  49  Figure 2.16  Effects of AIC1 , NaCl and C a C l on activities of M g C l + H C l mixture 3  2  53  2  Figure 3.1  Experimental equipment set-up  57  Figure 3. 2  Experimental set-up for thermodynamic measurement  58  Figure 3. 3  Experimental set-up for leaching test  58  Figure 4.1  Log ynci values: experimental, calculated by the Harned equation vs. reference and the calculated values by the Meissner method  66  Figure 4. 2  Solubility dependence of M g C l on acidity and the temperature  67  Figure 4. 3  Pyrite leaching: Effects of acid concentration, temperature and time  69  Figure 4. 4  Pyrite leaching: Effect of M g C l concentration at 6 0 ° C 2  69  Figure 4. 5  Millerite leaching: N i extraction  71  Figure 4. 6  Millerite leaching: Fe extraction  71  2  ix  Figure 4. 7  Violarite leaching: Ni extraction (2m MgCl )  73  Figure 4. 8  Violarite leaching: Co extraction  73  Figure 4. 9  Violarite leaching: Fe extraction  73  2  Figure 4.10  Troilite leaching: Fe extraction at 2 5 ° C (2m M g C l )  75  Figure 4.11  Troilite leaching: C u extraction at 2 5 ° C  75  Figure 4.12  Troilite leaching: Fe extraction at 25 & 60°C  75  Figure 4.13  Heazelwoodite leaching: Ni extraction (2m MgCI )  76  Figure 4.14  Chalcopyrite leaching: Metal extractions  77  Figure 4.15  Low M g O concentrate: Effect of leach time (10m HCl-2m M g C l at 60°C) 80  Figure 4.16  Effect of acid concentration (2m M g C l , t=2 & 4 hr at 100°C)  80  Figure 4.17  Effect of C u C l addition (6m HC1, t=4 hr at 100°C)  81  Figure 4.18  Effect of F e C l addition (6m HC1, t=4 hr at 100°C)  81  Figure 4.19  The dissolution of magnesium (6m HC1, t=4 hr at 100°C)  81  Figure 4. 20  High M g O concentrate: Effect of leaching time (6m HC1 - 2m MgCI at  2  2  2  2  2  3  2  100°C)  82  Figure 4. 21  Effect of acid concentration (2m M g C l , t=lhr at 100°C)  82  Figure 4. 22  Effect of C u C l addition (6m HC1 - 2m M g C l , t=lhr at 100°C)  82  Figure 4. 23  Effect of F e C l addition (6m HC1 - 2m M g C l , t=lhr at 100°C)  82  Figure 4. 24  Dissolution of magnesium (6m HC1 - 2m M g C l , t=lhr at 100°C)  82  Figure 4. 25  Matte leaching: Ni extraction at 60°C (2m M g C l )  85  Figure 4. 26  Matte leaching: Co extraction at 6 0 ° C (2m M g C l )  85  Figure 4. 27  Matte leaching: C u extraction at 60°C (2m M g C l )  85  Figure 4. 28  Matte leaching: Fe extraction at 6 0 ° C (2m M g C l )  85  Figure 4. 29  Matte leaching: Metal extractions at 100°C (2m M g C l )  Figure 4. 30  X-ray patterns of pyrite and pyrite leach residue (10m HCl-2m M g C l at  2  2  3  2  2  2  2  2  2  2  85  2  2  60°C)  87  Figure 4. 31  S E M picture of pyrite leach residue (10m HCl-2m M g C l at 60°C)  88  Figure 4. 32  X-ray patterns of millerite and its leach residue (10m HCl-2m M g C l at  2  2  60°C)  89  Figure 4. 33  X R D patterns for violarite mineral sample  90  Figure 4. 34  Compared X R D patterns for violarite and leach residue  91  Figure 4. 35  X-ray patterns of chalcopyrite and its leach residue (7m HCl-2m M g C l at 2  100°C)  92  X  Figure 4. 36  X-ray patterns of low M g O concentrate  93  Figure 4.37  Overlapped X-ray patterns of low M g O concentrate and its residue (8m HCl-2mMgCl )  94  2  Figure 4. 38  X-ray pattern of low M g O concentrate residue (8m HCI-2m M g C l at 2  100°C) Figure 4. 39  94  S E M image of low M g O concentrate leach residue (8m HCl-2m M g C l at 2  100°C) Figure 4. 40  95  X-ray pattern of low M g O concentrate and its leach residue (6m HCl-0.5m MgCl -0.5m CuCl ) 2  Figure 4. 41  96  2  S E M of low M g O concentrate leach residue (6m HCl-0.5m MgCl -0.5m 2  CuCl atl00°C)  97  2  Figure 4. 42  X-ray patterns of high M g O concentrate and its leach residue (6m HC1 and 2m M g C l a t l 0 0 ° C )  98  2  Figure 4. 43  S E M image of high M g O concentrate leach residue (6m HC1 and 2m M g C l  2  at 100°C)  98  Figure 4. 44  S E M image of high M g O concentrate leach residue: Selected spots  99  Figure 4. 45  X-ray patterns of high M g O concentrate and its leach residue (6m HCl-2m MgCl -0.05m C u C l at 100°C) 2  Figure 4. 46  100  2  S E M image of high M g O concentrate: (6m HCl-2m MgCl -0.05m C u C l at 2  2  100°C) Figure 4. 47  100  S E M image of high M g O concentrate leach residue: (6m HCl-2m M g C l 2  0.2m C u C l at 100°C)  102  2  Figure 4. 48  Compositions of high M g O concentrate leach residue (6m HCI-2m MgCI 2  0.2m FeCI at 100°C)  102  3  Figure 4. 49  X-ray patterns for matte and its leach residue (6m HCl-2m M g C l at 100°C) 2  :  103  Figure 4. 50  S E M picture of matte leaching residue (6m HCl-2m M g C l at 100°C)  104  Figure 4. 51  S E M picture of matte leaching residue: Selected spots  104  2  xi  ACKNOWLEDGEMENTS  I would like to express m y sincere gratitude to m y supervisor D r . D a v i d Dreisinger for his enormous support o f my studies from the beginning to the end. This would never come to completion without his encouragement and thoughtful guidelines throughout these years. I am grateful for the opportunity to be a graduate student under his supervision at U B C . I would to extend m y thanks to D r . Eric Roche, Principal Research Scientist at the B H P Newcastle  Technology Center  i n Australia,  for  his  coordination o f m y  research  and  encouragement. Special thanks are given to Dr. Berend Wassink for his everyday assistance i n the lab, and to our hydrometallurgy group fellows, whom I have developed a good friendship with during these years, for always being ready to discuss m y problems and giving me a hand when necessary. The other faculty and staff members at the Materials Engineering Department o f U B C are friendly and welcoming, it is a nice community. Furthermore, the University o f British Columbia is a great institution academically and an enjoyable place socially. The author also would like to acknowledge B H P Billiton, Australia for their financial support and providing concentrate and matte samples and related mineral analyses. Finally, I would like to thank to my wife Khulan, son Bilguun and baby girl Nomuun for being "brave" by themselves not interrupting m y studies at any time and supporting me as always.  Xll  CHAPTER 1 INTRODUCTION Worldwide nickel production comes from two distinct natural resources: sulfide ores and laterite ores. Pyrometallurgy or hydrometallurgy have been utilized individually or i n combination for the production o f nickel and associated metals from these resources. The sulfide ore processing consist of, traditional ore dressing to a concentrate, and the concentrate smelting to matte. T w o pyrometallurgical processes have been commercialized to treat nickel laterites; smelting to ferronickel, and smelting i n the presence o f a sulfur-containing compound to produce nickel matte. Further, nickel matte may be processed hydrometallurgically to final metal products. Pyrometallurgy is well proven in the field o f sulfide concentrate processing; however, it has limited applicability for processing low-grade and dirty concentrates due to energy cost and environmental restrictions. Moreover, it requires high capital cost. O n the other hand, hydrometallurgical processing options for base metal production have several advantages when compared with pyrometallurgy. This route eliminates air pollution and yields higher product quality at lower capital and operating costs. Because o f these advantages, two principal hydrometallurgical processes for the recovery o f nickel from oxidized ores have been commercialized: Caron process and the H i g h Pressure A c i d Leach ( H P A L ) process. The Caron process is preceded by a reduction roasting process. Five plants that utilize the Caron process were commercialized between 1952-1986. The major disadvantage o f the Caron based processes is its front-end ore drying and calcining stage, which makes the process intensive with respect  to energy cost. The first pressure  acid leaching ( P A L ) plant for laterites  was  commercialized i n 1959 i n Cuba followed by three H P A L plants i n Western Australia i n m i d 90's. Two new plants are expected in N e w Caledonia (Inco) and Australia ( B H P Billiton) for laterite resources. For sulfide concentrates, the processes such as P L A T S O L , C E S L and Activox are well developed. A l l these are based on pressure leaching. In addition, Inco is planning a pressureleaching route for Voisey Bay's sulfide concentrate. The pressure leaching processes work reasonably well for most o f the oxide ores and sulfide concentrates. The major disadvantage o f these processes lies on the large amount o f acid added (laterites) or produced (sulfides). Both solid residue and solution from leaching are neutralized. Therefore, P A L processes are mostly used to treat limonite (low acid consuming) ores rather than saprolite (high acid consuming). Clay content (high A l and MgO). i n an ore is the limiting factor o f the P A L usage. The  modern operations successfully utilize the advanced methods such as solvent  extraction, ion exchange, and pyrohydrolysis for solution treatment. Extraction reagents that  1  operate i n any media have been developed. The shortcomings o f the existing hydrometallurgical processes rest on the autoclave leaching unit for acid leaching processes, and on the ore drying and reductions stages for Caron based processes. A s mentioned above, feed characteristics are limiting criteria for those pressure-leaching circuits. The high-pressure vessels are the most expensive, energy-consuming and non-standard equipment in any hydrometallurgical circuit. To overcome shortcomings o f the existing technologies, the chloride-processing option has recently entered a period o f renewed interest and investigation because o f its advantageous leaching power. The strong leaching power eliminates the use o f a pressure vessel and its related costs. Second, processing in chloride media tolerates high clay content (high A l ) and high acid consuming (high M g ) feed. A l contributes to the increase o f the proton activities, whilst M g is leached and recovered i n subsequent stages. A t an industrial level, chloride processes proved their viabilities economically and technically. Three refineries worldwide are already operating to process nickel sulfide mattes based on chloride processes. Outokumpu developed the Hydrocopper process to treat chalcopyrite concentrates i n cupric-sodium-chloride media. In the case o f nickel, Jaguar N i c k e l developed a process to treat laterites i n the mixture o f magnesium chloride and hydrochloric acid at atmospheric pressure. This mixture calls for specific attention because o f the unique property o f M g C b to be decomposed and recycled. While many excellent research works have been done on chloride metallurgy, little attention has been paid to the mixture o f hydrochloric acid and the magnesium chloride. Recently, Jaguar N i c k e l proposed the possibility o f applying this mixture to process laterite resources. The gap to apply this mixture to process sulfide sources remains open. This application is attractive because the process takes place at atmospheric pressure and the reagents are recyclable. Magnesium  chloride solutions can be pyrohydrolyzed to reagents hydrochloric acid and  magnesium oxide for reuse. Therefore, this research is focused on treating sulfide concentrates o f nickel/cobalt i n the mixture o f magnesium chloride and hydrochloric acid at atmospheric pressure. More specifically, the scope o f this work is as follows: 1. To characterize thermodynamic properties o f M g C ^ - H C l mixture by experimental and modeling approaches; 2. To study the dissolution chemistry o f selected sulfide minerals and concentrates i n this mixture as a function o f acid concentration and temperature.  2  CHAPTER 2 LITERATURE REVIEW  This chapter consists o f two parts. The first part reviews existing processes and plant practices for nickel production with more emphasis on chloride based technologies. The second part reviews thermodynamics o f aqueous chloride system focused on the mixture o f magnesium chloride and hydrochloric acid.  2.1  Nickel-cobalt production  2.1.1  General  N i c k e l is produced from two distinct natural resources: sulfide ores or laterite (oxidized) ores. Cobalt is produced as a byproduct o f copper i n Africa and as a byproduct o f nickel elsewhere. Sulfide ores are generally' deep and hard-rock type deposit, which is mostly mined by open-pit and underground mining techniques, followed by concentrating, smelting and refining. About 30% o f the world's nickel resource on land is i n sulfide ore bodies; however, it accounts for about 60% o f world nickel production. Laterite ores are found where prolonged tropical weathering (laterization) o f "ultramatic" rocks occurred, forming clay-rich "soft" deposit. This type o f deposit accounts for over 70% o f the nickel resources; however only 40% o f the nickel production comes from this source [1,2]. Distinct processes have been applied for the production o f nickel and cobalt from both o f these resources. In addition, a number o f processing options are developed to treat sulfide concentrates and matte products. The following sections present a brief summary o f representative processes and plant practices. The hydrometallurgical route, more specifically chloride media at atmospheric pressure, draws more emphasis to the use o f the mixture o f magnesium chloride and hydrochloric acid.  2.1.2  Processing Options The processes for metal production from natural ores fall into two general categories:  pyrometallurgy and hydrometallurgy. Either individual or combination routes have been applied i n the metal industry. Historically, pyrometallurgical route dominated the industry o f extracting metals from their sulfide sources; recent developments o f hydrometallurgy enabled the treatment,  3  not only oxide sources, but also sulfide products. The hydrometallurgical processes can be classified in terms o f media as ammonia, sulfate and chloride.  2.1.2.1  Sulfide Processing  Both pyrometallurgy and hydrometallurgy routes have been used for nickel sulfide processing. Pyrometallurgical processing o f sulfide ore is carried out i n three stages: concentrating, smelting and refining. The concentrating stage comprises o f crushing, grinding and ore dressing. Ore is crushed in several stages and fed into grinding mills along with process water. The m i l l discharge-slurry is classified by particle size and the fine fraction is fed into flotation cells, where reagents (collector, modifier, frother, air etc) are added. Based on the hydrophobic or hydrophilic properties o f particle surfaces, certain sulfide minerals are attached to bubbles, separated from gangue and unwanted sulfide minerals. The concentrate, containing about 12 to 20% o f nickel (or about 30% o f N i + C u in Canadian operations), is thickened, dried and sent to smelters for further processing. D r y concentrate is mixed with flux (silica sand) and fed into the smelting furnace. In the furnace,  the mixture reacts with oxygenated hot air and oxidizes almost  instantaneously.  Afterward, the smelted mixture is collected i n a settler where the molten metal sulfide (matte) and the slag are separated. N i c k e l matte sinks to the bottom o f the settler, whereas the slag floats on top. N i c k e l matte contains about 75% N i - C u (40-70% N i , and 5-35% Cu), up to 24% S, and less than 1%) o f Fe. Typical slag contains about 0.1-1.0% o f N i . A converter m a y b e utilized to upgrade nickel content o f the matte by blowing oxygen into the matte converting residual sulfides to metal. U p to this point, the sulfide ore is processed by a combination o f traditional routes o f ore dressing and smelting. Further refining o f matte may be done hydrometallurgically. Matte refining comprises re-grinding, leaching and reduction. A n example o f a refining plant w i l l be discussed i n part 2.1.3. Despite smelting routes, a number o f hydrometallurgical processes have been developed for sulfide concentrates. Sherritt Gordon (now Corefco) o f Canada developed and commercialized a pressure leaching process in ammonia-ammonium sulfate media i n 1954. The plant is still i n successful operation in Fort Saskatchewan, Alberta treating sulfide concentrate with high cobalt content [14, 15]. Similar plants have been built at Kwinana (Australia) and Springs (South Africa). Hydrogen gas is used to reduce nickel ions and the reduced product precipitates as nickel metal. In  4  addition, a number o f processes such as the P L A T S O L process by Polymet M i n i n g Company, H I K O by O U T O K U M P U , Activox process by Western Mineral Technology Pty L t d ( W M T ) , C E S L nickel process by Cominco Engineering Service L t d , Sumitomo, N i p p o n (all high pressure) and BIONTC (atmospheric pressure) process by B H P Billiton have been developed. Recently I N C O announced the startup o f a hydrometallurgical demonstration plant (pressure leaching in mixed sulphate-chloride media) in Argentia, Newfoundland for Voisey B a y sulfide concentrate. These pressure-leaching processes are a new approach to eliminating the conventional smelting routes for the processing o f nickel sulfide concentrates and laterite ores.  2.1.2.2  Laterite Processing Because o f their complex mineralogical compositions, there is no distinct processing  option for laterites [20]. A variety o f flowsheets are developed, which fall into two general categories o f pyrometallurgy and hydrometallurgy. Two pyrometallurgical processes have been commercialized to treat nickel  laterites;  smelting to ferronickel, and smelting i n the presence o f a sulfur-containing compound to produce nickel matte. Since the  objective  o f this research  is centered  on hydrometallurgy,  the  pyrometallurgical routes w i l l not be discussed further. Table 2.1  Laterite Processing Plants based on the Caron process [1,2,13] Product  Period  Cuba  Capacity ktNi/yr 23  N i oxide  1952-present  Philippines  35  Briquettes  1974-1986  18  Briquettes  10  Briquettes  Operation  Company  Country  Nicaro Surigao Refinery at Nonoc Greenvale/Yabulu  Nicaro Nickel Co. Marinduque Mining & Industrial Co. Freeport/Metals Exp. Queensland Nickel/BHP Billiton  Niquelandia/Sao Paulo Punta Gorda  Australia  1974-present  Companhia Niquel Tocantins  Brazil  17.5  electronickel  1981-present  Union del Niquel  Cuba  31.5  N i oxide  1986-present  Two principal hydrometallurgical processes for the recovery o f nickel from oxidized ores have been commercialized: Caron process and the H i g h Pressure A c i d Leach ( H P A L ) process. A patent for the Caron process was granted to Professor Caron i n 1924. The process leaches metal i n ammonium media at atmospheric pressure, after an ore has been reduced by roasting. Nicaro N i c k e l Co., Cuba operated the first plant that utilizes the Caron process. Subsequently, four plants that utilize the modified Caron process were commissioned i n the early 70's and 80's (Table 2.1).  5  The Nonoc flowsheet, a variation o f the Caron process, was actually modified by Sherritt Gordon of Canada. These are the only operations based on the Caron process, and are still i n operation, with the exception o f Nonoc. A s a representative o f these operations, the Queensland Plant w i l l be covered i n section 2.1.3. The pressure acid leaching o f laterite ores with low magnesia was developed by Freeport for the M o a B a y deposit i n 1959. This process utilizes technology licensed by Sherritt Gordon. The M o a B a y operation is the precursor o f all o f the modern day H P A L operations for laterite ores.  K e y H P A L operations i n the past and future are presented i n the following table. M o r e  details of published resources w i l l be introduced shortly. Table 2. 2  Laterite Processing Plants based on H P A L [1,  Capacity Product .ktNi/yr 25 Mixed sulfide 5 40 N i Briquettes 9 Electronickel  Operation  Company  Moa Bay debotllenecked Murrin Murrin Cawse  Freeport Sulfur General Nickel/Sherritt J V Anaconda Centaur  Australia Australia  Bulong  Resolute/Preston Resources  Australia  7  Electronickel  1999-2003  Inco Ltd.  New Caledonia  60  N i Oxide  Projected in 2007  B H P Billiton  Australia  40  N i Hydroxide 2006 Startup  Goro Ravensthorpe  2.1.3  Country  2,13]  Cuba  Period 1959-present 2000-present 1999-present 1998-present  Processes and Plant Practices All  processes and  operations described  below  are  aimed  to  treat nickel  sulfide  concentrates, sulfide mattes and laterite ores, hydrometallurgically. They generally fall into three categories in terms o f leach media: ammonia, sulfate and chloride.  2.1.3.1  A m m o n i a Pressure Leach: The Sherritt Gordon Process The Sheritt Gordon process is the first hydrometallurgical operation i n the world for  treatment o f nickel sulfides. The process treats sulfide concentrate, blend o f high-grade nickel concentrate and nickel matte with only minor process modifications. The first application o f this process was  i n Fort Saskatchewan,  Alberta i n 1954.  Since  1991 the  flowsheet  at Fort  Saskatchewan has been modified to refine mixed sulfide feed o f M o a Bay, Cuba with high cobalt  6  content. The final products are nickel briquettes, cobalt briquettes and all sulfur is recovered as an ammonium sulfate for fertilizer use. The modern Sherritt Gordon process flowsheet is extensively discussed i n the literature, and interested readers are guided to references 13-15 o f this work. This process was adopted by Western M i n i n g C o . , Australia at K w i n a n a plant for the treatment o f nickel sulfide concentrates i n 1970. Due to low nickel price, high-energy cost and the limited marketability o f fertilizer i n Western Australia during that time, the Kwinana plant opted for treatment o f nickel matte [10]. The plant i n Canada is still i n successful operation with minor modifications. The process is very energy intensive (200GJ/t N i from concentrate), which is a major issue i n some geographical locations [15]. 2.1.3.2 Ammonia-Ammonium Carbonate Atmospheric Leach: The Queensland N i c k e l Laterite Treatment Plant [87]  Queensland N i c k e l i n Australia and Marinduque M i n i n g and Industrial Corporation i n the Philippines commissioned plants that utilize the Caron process i n the early 1970's. The Queensland N i c k e l laterite treatment plant has had major changes to the Caron process flowsheet. Figure 2.1 illustrates the simplified flowsheet o f the modern plant. In both flowsheets, the reduced laterite ore is quenched in ammoniacal ammonium carbonate solution and leached i n aerated tanks. The original flowsheet included a hydrogen sulfide precipitation stage where virtually all cobalt and about 10% o f the nickel were recovered as a mixed sulfide. The mixed product was dried and shipped for further separation o f cobalt and nickel. Cobalt-free nickel pregnant solution from the previous precipitation stage is subjected to stripping by ammonia and carbon dioxide where basic nickel carbonate ( B N C ) precipitates. The B N C product is recovered by thickening and filtration, and the wet filter cake is dried and calcined i n a rotary k i l n to yield nickel oxide as a final product. In the modern Queensland nickel plant flowsheet (Figure 2.1), a solvent extraction circuit was introduced to improve plant performance on nickel recovery. The raffinate from the nickel extraction feeds into the cobalt precipitation stage. Extracted nickel is stripped by strong ammonia solution followed by nickel oxide production by the conventional steam strip and calcination process. A more recent improvement i n the process involves recovering the cobalt sulfide precipitate and after pressure leaching and solvent extraction with D 2 E H P A and L L X 8 4 Q N i , converting the cobalt to cobalt oxy-hydroxide C o O ( O H ) . The Caron based process, however, works well; the only concern that has risen is its frontend ore drying and reduction circuit. This high-energy consuming unit hinders, the economic  7  viability o f this process. Figure 2.1  Ammonia-Ammonium Carbonate Atmospheric Leach Flowsheet [87]  Laterite ore  CO+Hydrogen  {-  f  JCoal/Fuel Oil  Ore Drying/ Reduction  e s  Air  1  <  Aeration leach wash liquor Pregnant leach liquor CCD residue wash  Absorber solution  Steam Pre-boil stills  Ni SX LIX84QNI  Ni strip  CoS ppt  NH,  Steam  Tailings still  Residue to tailings  ammonia/ carbon^ dioxide  Absorbers/ [StrongNH, Solutioir condensers  I  T  Strip liquor  CoS Product  Product stills  NiC0 solution  I  Calcine  2.1.3.3  3  NiO  Reduction/ cintering  Ni products  Total Pressure Oxidation P L A T S O L Process [84] Polymet M i n i n g Company developed the P L A T S O L process to treat copper-nickel-cobalt-  P G M sulfide concentrate from the Northmet deposit i n Minnesota. Figure 2.2 illustrates the simplified flowsheet o f the P L A T S O L process. The process includes a pressure autoclave that allows high levels o f base and precious metal extractions from concentrate under total oxidation  8  conditions at 225°C and about 100 psig o f oxygen overpressure. 10-20 g/1 HC1 is added to the leach circuit to extract P G M and A u as chloride complexes. The solids are separated from the leach solution and washed. The washed solid residue is sent to waste disposal and the solution advances to metal recovery. Figure 2. 2  Proposed P L A T S O L flowsheet for C u - N i - C o - P G M sulfide concentrates from NorthMet Mine [84] Cu-Ni-Co-PGM mixed sulfide concentrate Total Pressure Oxidation 225°C, 100 psig  I  eo  S/L Separation  SO,  01 cu  3  Fe to Fe 3+  >  2+  Solid  Wash  waste disposal  reduction  NaSH-  s  U  S o  P G M Precipitation  3  PGM Precipitate  limestone s  05  Excess acid & Fe  Neutralization of excess acid  Bleed stream for Ni, Co r recovery Oxyhydrolysis  I  Cu removal  I  -Gypsum  Cu SX  IT: Cu E W  T  Cu cathode  MgO Ni-Co Precipitaion Ni-Co'mixed hydroxide  The precious metals are selectively precipitated with the addition o f sulfide ion. The solution is treated with limestone to neutralize excess acid followed by SX-EW to produce cathode copper. A major portion o f the raffinate from copper extraction is recycled to the autoclave to  9  maintain the water balance and build nickel and cobalt composition. The balance o f the solution is bled to nickel and cobalt recovery. This solution is treated by oxyhydrolysis where excess acid and iron are removed followed by copper removal. The purified solution is treated with magnesium oxide to precipitate mixed nickel and cobalt hydroxide. The commercial application o f the P L A T S O L process at NorthMet is expected in 2008.  2.1.3.4  The Activox Process at Tati N i c k e l M i n e i n Botswana Western Minerals Technology ( W M T ) has made a significant step to commercialize its  patented (Activox) technology. W M T commissioned a hydrometallurgical demonstration plant at the Tati N i c k e l M i n e i n Botswana in 2004. Figure 2. 3  The Activox Process Flowsheet at Tati Nickel Mine [85]  i  Sulfide concentrate Ultra fine grinding H SQ 2  HC1,0,  4  Activox Leach 100-110°C, 1100 kPa  I I  S/L Separation  Solid  Wash  To P G M Recovery  Cu SX  2 stages of Fe removal Co SX Na C0 2  3  Co Precipitation  I  Cu E W Cu cathode  1, Ni SX  3£  ^^^^^^^^  Co Product  ammonia  NiEW  Quicklime  J  I  Ammonia Amtrw Recovery Steam Ammonia Stripping  Ni cathode Tailings Dam  10  The sulfide concentrate is re-ground to P80=10um. The ultra-fine ground feed for the autoclaves is diluted from 50% solids to 30% solids by the addition o f copper raffinate. Sulfuric acid, oxygen and sodium chloride are added into the autoclave to catalyze the oxidation o f sulfide minerals. After leaching, solids and liquids are separated, and the solids are subjected to C C D washing followed by P G M recovery. Copper is first solvent extracted from solution followed by electrowinning to produce cathode copper. Raffinate from copper solvent extraction is partially recycled into the leaching unit, whereas the remaining solution advances to cobalt solvent extraction. The cobalt is precipitated by sodium carbonate and recovered. The cobalt free solution from C o solvent extraction advances to N i solvent extraction followed by N i electro-winning. The barren solution is subjected to ammonia recovery with lime; recovered ammonia is recycled to the nickel and cobalt extraction circuits.  2.1.3.5  Additional Processes for Sulfide Concentrates  In addition, several other processes have been developed for the treatment o f sulfide nickel concentrates. OutoKumpu (Finland) developed a process called H I K O that consists o f nickel sulfide ore benefication and concentrate leaching stages. This process was used for treatment o f nickel sulfide concentrates at Hitura mine [86]. Cominco Engineering Service L t d . ( C E S L ) developed flowsheets, i n which Pressure A c i d Leach ( P A L ) was involved, for both laterite ores and sulfide concentrates [21]. The C E S L nickel process was developed based on the success o f the C E S L copper process, and is aimed to treat nickel, cobalt and copper containing sulfide concentrate. The C E S L nickel process begins with a pressure leaching step to put nickel, cobalt and copper into solution. Pressure leaching takes place at 150°C, in solutions containing up to 60g/l free acid with the addition o f up to 12g/l free chloride. The leaching is followed by solution purification to remove copper and other impurities such as iron and zinc. The copper is then treated by S X - E W to cathode copper. The purified solution is treated by lime to co-precipitate nickel and cobalt. The mixed hydroxide is re-dissolved in an ammonium sulfate media to produce a relatively pure solution o f nickel and cobalt as diammines. Cobalt, and then nickel are separately recovered from the diammine solution by individual S X - E W circuits, producing the respective metals as cathodes. Furthermore, the Sumitomo process to treat nickel sulfide concentrate and the Nippon process for cobalt sulfides are developed [10, 13]. A l l o f these processes are based on pressure acid leaching. Inco or its subsidiary V B N C (Voisey B a y N i c k e l Company) commissioned m i l l and  11  concentrating plant earlier this year at the Voisey B a y deposit. V B N C  is also planning  hydrometallurgical (pressure leaching circuit) treatment for its concentrate to make final products. The V B N C hydrometallurgy process is currently being tested at a demonstration plant at Argentia, Newfoundland. B H P Billiton developed the B I O N I C process for nickel sulfide concentrates as an alternative technology to high-pressure technologies [16]. This technology relies on the biological oxidation o f ferrous to ferric. Ferric ion then oxidizes the sulfide minerals. This eliminates the use o f a pressure vessel.  2.1.3.6  H i g h Pressure A c i d Leaching: M o a B a y Project High-pressure acid leaching o f laterite ore with low magnesia has been i n operation since  1959. Freeport Sulfur built the M o a B a y plant with the purpose o f finding a market for sulfur. The M o a B a y operation has faced several flowsheet changes, difficulties because o f political reasons, before finally entering a period o f stable operation since forming joint venture with Sherritt International i n 1994. The recent flowsheet o f the M o a B a y operation is presented i n Figure 2.4. Figure 2. 4  Pressure Acid Leaching Moa Bay Flowsheet [14] TAILINGS  INE SERPENTINE REJECT!  Ore Preparation  MINE  SteamllH SQ  O/F  ORE|  2  Ore Thickeners  2  Product Thickeners  Precipitation ^1  *1  J  O/F| WASTE LIQUOR  1  GYPSUM SLURRY  U/F  JH S  SULPHIDES  CCD Washing  LEACH U/F  LIMONITE  Ni-Co  4  Neutral. Thickeners  0/F  C r , Fe Reduction 6 +  Neutralization *1  ^1  3+  LIME STONE  A series o f washing and screening steps rejects high acid consuming serpentine before leaching. This rejection is based on the particle sizes since most o f acid consuming serpentine is present as bigger particles. The leaching takes place i n vertical Pachuca type reactors at 250°C and 45 atm pressure. Slurry is directed to a seven stage C C D , and raw liquor is treated with hydrogen sulfide gas to reduce C r , F e 6 +  3 +  and to precipitate copper as copper sulfide. Clarified solution is  subjected to acid neutralization by Coral limestone, followed b y nickel and cobalt precipitation with addition o f hydrogen sulfide gas. Thickened product is filtered, dried and shipped to Fort Saskatchewan, Alberta for further refining.  12  Modern operations for laterite treatment  Successful operation o f M o a B a y has resulted i n several additional pressure leach operations. The modern day H P A L operations are practiced i n Western Australia at Bulong (now closed),  Cawse  and  Murrin  Murrin  to  treat  laterite  ores.  B H P Billiton  is planning  hydrometallurgical processing o f the upgraded laterite ore at its Ravensthorpe nickel project. This project uses the Enhanced Pressure A c i d Leach process to produce a mixed nickel and cobalt hydroxide as an intermediate product. C V R D o f Brazil announced the development o f the Vermelho N i c k e l Project. The project w i l l use a high-pressure acid leaching to process nickel laterite. Inco owns a nickel laterite deposit at Goro i n N e w Caledonia and are planning to utilize pressure acid leaching circuit. A s representatives o f these processes, Western Australian and I N C O operations are briefly summarized in the next sections. U n l i k e M o a Bay, these operations utilize more recent technologies such as solvent extraction and electro-winning to produce cobalt and nickel as final products.  2.1.3.7  Cawse Project The Cawse project is located 45 k m northwest o f Kalgoorlie, Australia. The plant uses  250000 tons o f sulfuric acid to produce 8500 tons o f LME-grade nickel and 1700 tons o f cobalt as cobalt sulfide annually. A c i d consumption at this plant is about 360 k g o f sulfuric acid per ton o f ore. The acid is provided by B H P Billiton's Kalgoorlie nickel smelter and imported sulfur. The flowsheet o f Cawse project is shown below. The leaching process takes place at 250°C under 45 atm pressure to dissolve nickel and cobalt. After autoclaving, most impurities are removed by adding limestone. Magnesia is added to precipitate the nickel and cobalt as mixed hydroxide slurry. U n t i l this point, the solution treatment takes place i n a sulfate media. Then the mixed hydroxide is leached in ammonium media. The pregnant leach solution is contacted with the organic phase, which contains the L I X 8 4 , to extract nickel. The nickel is recovered as a cathode product after stripping the loaded organic and electrowinning. The raffinate from the N i extraction is subjected to C o S precipitation by treating the solution with ammonium sulfide.  13  Figure 2. 5  High Pressure Acid Leaching Cawse Flowsheet [87] Ni-Co ore  Laterite ore • Screen upgrade Residue  •<  MgO-|  CCD  Lime—H  Ni/Co Hydroxide Precipitation  NH,  Ammonia leach  H  Ni SX LIX84 I  Crushing Grinding  I  Pressure leaching @250°C Fe Precipitation  H SQ 2  4  Limestone  NiEW Ni Cathode  (NH ) S-^ 4  2  Co Precipitation  Co Sulphide  The Cawse project underwent some initial difficulties at the startup and was sold to the U S O M G group. The O M G Company ships the mixed N i - C o product to their refinery i n Finland.  2.1.3.8  Bulong Project The Bulong process involves high temperature, acid pressure leaching followed by solvent  extraction and electrowinning for nickel recovery. The plant consumed about 250000 tons o f sulfuric acid to produce 9000 tons o f nickel and 700 tons o f cobalt annually, before shut down. The leach solid residue was neutralized for returning to the tailing. The simplified flowsheet o f Bulong is illustrated below. After removing some impurities by adjusting p H and E h , the whole process stream is subjected to C o solvent extraction using Cyanex 272. After the organic is stripped, the solution is treated by hydrogen sulfide to reject M n , M g and C a . Cobalt precipitates as C o S . This product is pressure leached in an acidic environment. Other impurities such as Z n and C u are dissolved with Co. Z n is removed by D 2 E H P A extraction and C u is removed by ion exchange. Cobalt is electrowon from the purified solution. The raffinate from cobalt solvent extraction goes to the N i extraction circuit with Versatic acid extractant followed by N i electrowinning. The Bulong  14  flowsheet experienced major operating problems. During cobalt extraction, Cyanex 272 extractant leaked into the Versatic acid solvent extraction circiut. Cyanex 272 extracts calcium at p H 6.5, resulting i n gypsum precipitation and the fouling o f the solvent extraction in the recovery o f nickel. Figure 2. 6  High Pressure Acid Leaching Bulong Flowsheet [87]  Laterite ore •  Ore Preparation  Pressure leaching  Gypsum & Fe/Zn waste*  Neutralization  CCD  -H S0 2  4  — Limestone Residue  Co SX CYANEX272  NH,  Ni SX Versatic acid  -  NH  Ni E W  •  Ni Cathode  Acid redissolution of CoS cake  Co E W  •  Co Cathode  Zn SX D 2 E H P A  C u Removal IX  •  I  Co, M n , M g , C a , Zn, Cu^r Mn, Mg, C a ^ — |  Sulphide precipitation  3  O  I  NH, Zn  2.1.3.9  I  Cu  Murrin Murrin The M u r r i n M u r r i n process requires 500000 tpa o f imported sulfur to produce 45000 tons  o f nickel and 3000 tons o f cobalt annually. M u r r i n M u r r i n uses an acid leaching process followed by sulfide precipitation to make a mixed sulfide intermediate product followed by nickel and cobalt refining utilizing oxygen leach, solvent extraction and hydrogen reduction to metal products. The plant produces 150000 tons o f ammonium sulfate by-product annually for fertilizer use.  15  Figure 2.1  High Pressure Acid Leaching Murrin Murrin Flowsheet [87] Laterite Ore  Ore Preparation  I  Pressure leaching Gypsum & Fe/Zn waste  H S gas-  H  2  gas.  Neutralization  CCD  I  4  Calcrete Residue  I  Co Reduction  Co briquettes  2  Pressure oxidation leach  Ni/Co sulphide precipitation  Sintering  H S0  H,  Co SX CYANEX272 ^ Ni stream Ni Reduction  J  -NH  3  ^Ammonium sulphate  Sintering  Ni briquettes The processing principle o f M u r r i n M u r r i n is very similar to Cawse. The P A L leaching is followed by several stages o f solution purification treating acidic solution, and C o / N i  are  precipitated with hydrogen sulfide gas. This precipitated product is leached i n an acidic environment, unlike the Cawse flowsheet. The C o is extracted with Cyanex 272. Each stream o f Co and N i is subjected to hydrogen reduction to recover individual metals. Technologically, all H P A L operations have proved their viability; however, economically they face constraints. Both ore leaching and slurry neutralization are performed with significant cost.  2.1.3.10  Inco Laterite Process  Inco owns the nickel laterite deposit at Goro in N e w Caledonia. The Goro project involves H P A L circuit i n its flow. L i k e H P A L operations i n Western Australia, the solid residue is neutralized by lime and calcium carbonate before it is discharged to tailings. The leach solution is subjected to several stages o f solution purification for acid neutralization, iron removal and C u is removed by ion exchange.  16  Figure 2. 8  High Pressure Acid Leaching Goro Flowsheet [87] Saprolitic or limonitic ore  Feed Preparaion  f^-^water  1 Pressure leaching  H S0 2  4  CCD  H S0 2  4  CaC0 Ca(OH).  Cu Removal IX  3  i  i.  Ni & Co SX Cyanex301  HC1  •  water  Zn Removal IX i Ni & Co SX Alamine 336  water  NiCl pyrohydrolysis 2  Final neutralization Na CQ 2  Tailings  3  Co precipitation  P  CoCO,  Ni powder  C o and N i are bulk extracted by Cyanex 301 from clarified solution. Cyanex 301 extracts nickel and cobalt without p H adjustment. C o and N i along Z n are stripped using HC1 solution. C o and N i are separated with Alamine 336 extractant. The N i containing stream is subjected to pyrohydrolysis where N i is recovered as nickel oxide and hydrochloric acid is produced and recycled to the stripping circuit.  2.1.3.11  Chloride Leach Process: Falconbridge Refinery  Falconbridge  and  Societe le N i c k e l ( S L N ) have developed  the  hydrometallurgical  treatment for nickel matte refining i n chloride media and commercialized at Kristiansand, Norway and Sandouville-Le Havre, France, respectively. The flow diagram o f Falconbridge refinery is presented i n Figure 2.9. The matte is leached i n chloride solution near its boiling point at atmospheric pressure.  17  Figure 2. 9  Falconbridge Chloride Leaching Refinery Flowsheet [13]  Ni-Cu Matte  Ni-Cu Chloride '^^Solution  Chlorine  Ni-Cu Matte  f  Copper removal  Ni Leach Chlorine  Ni Carbonate  Iron removal  Residue  Ni/Co chloride solution  Air Roaster Ni-Cu Matte  h  ri  Cobalt Strip  TIO amine  Ni carbonate  rfc^e'rV k y noi  Copper Leach  PGlJ  te  Cobalt purificatioi  Chlorine  T  Cu Cathode  Nickel Purificatio  Chlorine  residue  Cu EW  Cobalt extraction  Chlorine  Co EW  t Co Cathode  — \  Pb/Mn  Ni EW Anolyte to leach Ni Cathode  Copper, iron and any other impurity metals are removed and recovered ahead o f C o / N i extraction.  Purified C o / N i solution is subjected to solvent extraction with trioctylamine, where  cobalt is extracted leaving a purified nickel pregnant solution. The nickel solution is purified again by chlorine and nickel carbonate to remove any trace elements, and N i is recovered by direct electrowinning. The cobalt loaded organic is stripped by lean electrolyte solutions o f cobalt, and the rich electrolyte is purified prior to cobalt electrowinning.  The copper content i n the feed,  which was leached and subsequently precipitated i n solid residue, is recovered as a cathode copper in a separate circuit. The S L N flowsheet is principally the same as that o f Falconbridge, except for the source o f the chloride lixiviant solution. In the S L N flowsheet, a ferric chloride solution is recycled to leaching from iron removal, whereas N i / C u chloride solution is recycled from the treatment o f C u containing solid residue in Falconbridge. In addition to these two plants, The Sumitomo refinery i n Japan utilizes chloride media for the treatment o f nickel matte. These three refineries are the only commercial operations o f nickel matte refining i n chloride media.  18  2.1.3.12  Atmospheric A c i d Chloride Leach ( A A L ) Process: Sechol Project  Jaguar N i c k e l Inc., investigated hydrometallurgical processing o f nickel laterite at the Sechol Laterite Project i n Guatemala. This process utilizes atmospheric leaching o f laterite ore i n acidic chloride media. The flowsheet consists o f four main stages: leaching in acidic chloride media, purification, precipitation and pyrohydrolysis. In the first stage, nickel and cobalt are substantially leached, rejecting most o f the iron and magnesium. In the next two stages, the impurity elements, such as calcium, aluminum and residual iron are discarded, and nickel and cobalt are recovered. In the final stage, hydrochloric acid and magnesia are recovered by pyrohydrolysis. The inventors o f this process claim that all process steps are successfully illustrated i n the scale o f commercial application. For instance, Falconbridge's refineries, as w e l l as Quebec Iron and Titanium plant, are excellent examples o f successful operations i n chloride media  at  industrial  scale.  The  purification  and  precipitation  stages  are  conventional  hydrometallurgical processes and pyrohydrolysis is practiced i n the steel pickling industries [22]. According to the developers o f this process, it can be low i n capital and operating costs since no pressure vessels are required and acid is recovered and reused with significant low cost, unlike other processes such as those i n Western Australia i n which the acid is neutralized with significant cost. O f course, energy is required for pyrohydrolysis and HC1 recovery.  19  Figure 2.10  Sechol Flowsheet for Laterite Treatment at Atmospheric Pressure [11,12]  i  Laterite Ore Tailing to Disposal Magnetic concentrate for sale  Benefication Non-Magnetic concentrate  I  Atmospheric Chloride Leach Water  To Disosal S/L Separation MgO Solution purification  S/L Separation  MgO  Mixed Ni^Co Hydroxide for sale Energy  I  U ,  + u X  Two-Stage Ni/Co precipitation  I  Water  S/L Separation  I  MgCL  Pre-Evaporation  Energy.  I  MgCL  Pyrohydrolysis Magnesia for sale or Recycle  HC1  20  2.1.4  Technology Summary: Shortcomings of the Existing Technologies  The review o f existing technologies for nickel and cobalt production may now be summarized. A number o f technologies have been running through several decades at industry level, while some others are just fresh from laboratory and pilot study and show promise to replace existing technologies. Pyrometallurgy is well proven i n the field o f sulfide concentrate processing; however it has started facing restrictions i n the modern world due to emission o f CO2, C O , SO2 gases to atmosphere and the limitation o f processing low-grade and dirty concentrates with high content o f A s , Pb, H g . Moreover, it requires high capital cost. Smelting to ferronickel proved its applicability for high nickel grade (saprolite type) laterites, whereas it is an impractical option to process limonite sources due to higher energy consumption. Hence, the hydrometallurgical process options are deemed suitable for limonite sources. O n the other hand, hydrometallurgical processing options for base metal production proved its several advantages over pyrometallurgy. This route eliminates air pollution and yields higher product quality at lower capital and operating costs. Despite its advantages, not all existing technologies in nickel production are suitable for global resources. The high-pressure acid technologies, however, work reasonably well for most o f the oxide ores and sulfide concentrates, they still face acid consumption constraints especially for high acid consuming resources. Therefore, P A L processes are mostly used to treat limonite (low acid consuming) ores rather than saprolite (high acid consuming). Clay content (high A l and M g O ) i n ore is a limiting factor o f the P A L usage. Moreover, the solid residue and solution from the pressure leaching circuit is neutralized with significant cost. On the other hand, ammonium technology can effectively treat higher acid consuming feed (high M g O laterite ores) and sulfide concentrates. The major disadvantages o f the Caron process are the ore preheating and drying stages. This makes Caron based processes very sensitive to energy cost. In general, it is unlikely that new ammonium hydrometallurgical plants would be put into operation. Existing plants and operations w i l l continue, since their capital is already invested. Recently, more attention has been put on P A L ( H P A L ) processes commercializing three plants i n Western Australia. T w o plants are expected i n N e w Caledonia and Australia for laterite resources, and one i n Argentia, N L for sulfide concentrate. The main advantage o f those modern operations is successful utilization o f advanced methods, such as solvent extraction, ion exchange,  21  pyrohydrolysis for solution treatment. Though all processes work well, the shortcomings o f the existing hydrometallurgical processes rest on the autoclave leaching unit for acid leaching processes, and on the ore drying and reductions stages for Caron based processes. The feed characteristics are limiting criteria for H P A L operations. Moreover, the high-pressure vessels are the most expensive and non-standard equipment in any hydrometallurgical circuit. To overcome shortcomings o f the existing technologies, the chloride-processing option has recently entered a period o f renewed interest and investigation, because o f its advantageous leaching power.  The strong leaching power eliminates the use o f pressure vessels and related  costs. Second, processing i n chloride media tolerates high clay content and high acid consuming feed. A t an industrial level, chloride processes proved their viability economically and technically. Three refineries in the world are already operating to process nickel sulfide mattes based on chloride processes.  Outokumpu developed the Hydrocopper process  to treat chalcopyrite  concentrates i n cupric-sodium-chloride media. In the case o f nickel, Jaguar N i c k e l developed a process to treat laterites i n the mixture o f magnesium chloride and hydrochloric acid at atmospheric pressure. This mixture draws specific attention, which w i l l be described shortly. There could be the possibility to process sulfide minerals and concentrates in chloride media at atmospheric pressure. Therefore, current research focused to treat sulfide concentrates o f nickel/cobalt i n the mixture o f magnesium chloride and hydrochloric acid at atmospheric pressure.  2.1.5  Why M g C h ? Uniqueness of this mixture A mixture o f strong magnesium chloride and hydrochloric acid creates a non-ideal aqueous  solution. First, proton activity i n this mixture increases from its ideal, which gives a strong leaching power. Second, water activity is reduced. Jaguar N i c k e l has reported that iron is easily hydrolyzed and precipitated, which may allow selective leaching o f cobalt and nickel over iron. Thermodynamically, HC1 solutions with divalent chlorides such as M g C l  2  create much  higher proton activity than univalent salts such as N a C l . Trivalent salts such as AICI3 create an even higher activity than univalent or divalent metal chlorides. Therefore, M g C l - H C l mixture is 2  ideal for high M g and clay (high A l ) content feed, which is an economical constrain for any other above-mentioned processes. Whilst A l cations contribute to increase proton activity at the same time decreasing water activity, M g cation may minimize dissolution potential o f magnesia from laterite lattices and M g containing concentrates due to common ion effects. Pyrohydrolysis is used to recover and recycle hydrochloric acid i n strong chloride  22  processes such as in Inco and Sechol. During this process, MgCh is one o f a few chloride salts that decompose unlike other alkali and alkali earth metal chlorides. The decomposed M g is recyclable as M g O [11, 12]. Excess M g O may be sold as a by-product. A few promising properties o f this mixture are mentioned here. In order to utilize specific properties o f chloride media, more detailed knowledge o f aqueous chloride solution is required. Therefore, the next part o f this chapter reviews the thermodynamics o f strong brine and hydrochloric acid mixtures.  23  2.2  Thermodynamics of aqueous chloride media  2.2.1  General  Thermodynamically, the mixture o f hydrochloric acid and chloride salts o f common base metals create very useful properties o f aqueous solutions o f relevance to hydrometallurgists. These mixtures can increase the proton activity by several orders o f magnitude due to metal ion hydration by water, which reduces the activity o f free water i n solution. The reduced water activity may allow selective leaching o f metals [11, 12]. O n the other hand, the chloride complexation with metal cations can enhance the solubility limit o f certain cations. These changes o f proton and cation activities in solution are the particular interest o f the hydrometallurgists. Recently, the mixture o f strong magnesium chloride and hydrochloric acid solution is proposed to be a good lixiviant to selectively leach nickel from saprolite/limonite mixture with good rejection o f iron along with high extractions o f nickel and cobalt [11, 12]. In order to utilize the specific properties o f this mixture for the purpose o f leaching sulfide minerals, proper understanding o f thermodynamic properties o f aqueous chloride solution is required. M a n y efforts have been made to measure and estimate activities o f ions in concentrated electrolytes. Sets o f data, applicable for aqueous chloride solutions, are provided by Robinson and Stokes [42] and Harned and Owen [54]. Unfortunately, all known thermodynamic properties o f acid chloride solution are limited to dilute solutions with ionic strength o f less than six at ambient temperature. Hydrometallurgical processes are expected to operate at the upper limits o f chloride concentration. Estimation methods followed by experimental verification (when applicable) w i l l be used to quantify the thermodynamic properties o f strong chloride solutions, more specifically focused on hydrochloric acid and its mixtures with magnesium chloride at 25-100°C. The estimation procedure requires thorough knowledge o f thermodynamic properties; namely: mean ionic activity coefficients; corresponding water activities; osmotic coefficients; and the hydration numbers. In addition, the formation o f chloride complexes is another important contributor i n the behavior o f leaching system. A l l mentioned thermodynamic properties w i l l be defined as completely as possible i n the following sections.  24  2.2.2  Fundamental expressions of aqueous chloride media The following expressions are commonly used for solute concentrations i n aqueous  solutions: mole fraction-x, molality-m and molarity-c. The molal (mol/kg solvent) scale is preferred over the others for thermodynamic calculation purpose because o f its independence o f temperature and pressure. Based on mass balance, the molar and molal scales can be related as follows: m, =c,./(/?-0.00l]Tc,.^.)  t - ) 2  Where, p-density o f the solution, Wj -the formula weight o f the i  t h  1  solute, c and m are molar and  molal concentrations, respectively. The ionic strength-I, relates to molal concentration by the following equation. / = 0.55>,mK For A that dissociates into:  A <=> [v B  (  +  +  where, v  +  2  )  + v_C~] it becomes  I = 0.5m [v zl v_zt] A  Z  +  (  2  2  a  )  are moles o f respective cations and anions, and z are the charge numbers. The  ±  ±  reduced activity coefficient T° defined i n Meissner method i n the next section is related to the ionic strength o f the solution. Furthermore, the mean ionic activity coefficient- y is related to the ±  reduced activity coefficient (r°) as shown here:  = (r°)  Y  (z+z  '  (2.3)  a =my ±  ±  and the mean ionic activity a itself is: ±  (2.4)  ±  where m is the mean ionic molality defined as: ±  m =(m *m ) v  ±n  v  Uv  (2-5)  where, v = v+ + v. K n o w i n g all these parameters, the partial molal free energy or the chemical potential Lij can be defined as: M  .=//,°+W?rin(a ) ±  (2.6)  M o r e definitions and applications o f those equations w i l l be covered in the following sections and in the attachments.  25  2.2.3  Estimation of activity coefficients in aqueous chloride media  2.2.3.1 Estimation methods o f activity coefficients i n aqueous chloride media  To precisely analyze thermodynamic properties o f strong chloride solution, it is important to start estimating/measuring accurate values for the participating ion activities. The initial effort to estimate the activity coefficients for electrolyte solutions was put forward by Lewis and Randall [30] (cited from 40) by relating the activity coefficient and the concentration o f an aqueous electrolyte solution. They related the ionic strength (I) based on the molal concentration as follows:  / = 0.5^>,.z, i  2 (  2  7  )  Continuing this work, Debye & Hiickel developed an expression for mean activity coefficient (y±) and the ionic strength: log/  +  =  Az^zJ '  0 5  (2.8)  A detailed description o f the constant A is reported with a value o f 0.5107 k g  172  mol"  1/2  at 25°C  [40]. Guntelburg [cited from 40, 54] has made improvements on this expression, taking ion size into account. Nevertheless, both expressions give fair results at ionic activity up to 1=0.1, all later improvements are based on this equation. Further improvements to calculate the mean ionic activity coefficients have been studied extensively by Guggenheim [56], Stokes & Robinson [42]; however, the validity o f those equations weakens in solutions o f molality greater than one m o l kg" . 1  Meissner [31-38] developed a more useful and straightforward method using a chart based on previously reported thermodynamic data. The Meissner chart is a family o f curves constructed by plotting T° (reduced activity coefficient) against I (ionic strength) for various electrolytes at 25°C. For a given solution, reduced activity coefficient (r°)  at any ionic strength can be  approximated from these graphs. Besides this graphical method, they also provided the following expression relating the reduced activity coefficients with ionic strength for pure electrolytes.  r° = [1 + B(\ + 0.U) -B]*exp[-AI q  m  / ( l + CTJ  (2.9)  26  where, A(25°C) = 0.5107, B=0.75 - 0.065q,  C = 1 + 0.055q * exp(-0.023 I ) and q is called 3  Meissner q-value which has different values for each electrolyte and at each temperature. Average values for the q are reported i n Meissner [37,38] and D i x o n [6] for selected electrolytes at 25°C. K n o w i n g q° at 25 °C, its value at other temperatures is obtained by the following empirical equation. q° = q° [l-0.0027(T-25)/z z )] T  25  l  2  ( 2  1 0 )  where, T i s the temperature, and zj, Z2 are the charge numbers of the dissociated salt. Meissner et al [31-38] also derived semi-empirical expression applicable to calculate mean activity coefficients for multi-component aqueous solutions. For a binary system such as a target of this research work-the M g C V H C l mixture, the equation can be reduced to:  ^ior  ^g r I0  w a  MgCT2  = io = io  g l o  g l 0  r  0 w c /  +o.5x iog (r^ 3  -  r°  MgCl2  o.5x, i o  1 0  /r^)  c / 2  (T° 1 r° ) MgCl2  g l 0  HCl  ( 2  l l a  )  (2.1 i b )  where, r ° refers to the reduced activity coefficient T. i n a pure component i having the same total ionic strength as the mixture, x i and x represent the ionic fractions of the respective cations. 3  Recently D i x o n [6] provided the generalized equation to calculate the reduced activity coefficient o f components for mixtures o f electrolytes as follows:  log^r^: = ( z , X / ^ „ i o g r ° +z Y i v iog r° )/i(z +z ) n  where,  1 0  ^  =  0  . ( . 5  z  J  J m  + z  .f  mJ  l0  mJ  i  j  (2.12)  /.. 2 z  In these equations, indices i and m refer to cations whereas j and n refer to anions. It is important to note that for equations 2.11-2.12, the reduced activity coefficients o f each species are calculated as i n equation 2.9 at the total ionic strength o f the mixture. Calculations obtained by using equations 2.11 or 2.12, give slightly different result as w i l l be shown i n sample calculations later. Meissner et al also provided an empirical expression for temperature dependences o f mean activity coefficients between 0-150°C at total ionic strength o f 1=10.  l o g r£ _io) = [1 - 0-005(7 - 25)] * l o g 10  (/  10  r°  5(/=10)  (2.13)  27  Combination o f this formula and the Meissner plot allows calculating mean activity coefficients at any temperature-T and at an ionic strength o f other than 10. These authors provided sample calculation i n their works. The expression i n 2.13 assumed that the isotherm for a given electrolyte at 25°C would coincide with that at some other temperatures, which is not true for most electrolytes. The dashed line on the Meissner's chart [37,38], designated by the subscript " r e f , w i l l be relatively unaffected by temperature. Applying this, the temperature effect can be estimated at any ionic strength below 20 by the following equations.  l o g r ° = ( 1 . 1 2 5 - 0.0057/) * l o g T ° - (0.125 - 0.0057) * log Y° 10  10  tog r^=-O.41/ /a  5  + / )+p.039/  ,/,  , / i  10  ( 2 ref  '  1 3 )  w  h  e  r  e  (2.14)  f t 9 1  Those expressions allow calculating the reduced activity coefficients (and then mean ionic activity coefficients) at any temperature not limited to ionic strength o f one value. Pitzer and co-workers [68] developed an expression (model) accounting for the effect o f ion-pair interaction and triple ion interaction. The latest modified Pitzer equation is more successful for higher concentrations up to six molal. Even though the Pitzer model is considered complex comparing to other models, it is considered the most precise fit to experimental data. R o y et al [43-44], as w e l l as K h o o ' s work [49-50] clearly demonstrates the use o f this equation for a variety o f mixed chloride systems. Bromley [39] developed the simplified version o f the Pitzer model. According to his work, the correlation between mean ionic activity coefficients o f strong electrolytes and ionic strength can be illustrated as shown below:  iogio r±  2,22  =0.511* 7 ° / ( l + 7 ° ) + (0.06 + 0.6B)I / ( l +1.5/ / z z_ f+BIIz 5  5  +  +  (2.15)  The Bromley B values are a function o f temperature and are reported for selected electrolytes; when data is not available, it can be calculated [39]. However, modifications have been made on both o f these models (Edwards [41] et al. extended this correlation up to 10-20 molal and between 0-170°C for aqueous ammonia solutions), the limitation remains up to 6 m for the chloride system.  28  Analyzing all these equations, methods and modifications to estimate the mean ionic activity coefficients, the Meissner method based calculations (the method described i n Meissner's original papers, or the generalized equations appear i n D i x o n ' s paper [6]) gave a reasonable estimation for activity coefficients at higher ionic strengths and at temperatures for strong chloride aqueous electrolytes. Hence, the Meissner method was selected for use i n this thesis.  2.2.3.2 Estimating activity coefficients by Meissner method  Taking the Meissner's theory as a basis, Peters [4] calculated the activity coefficients o f hydrochloric acid mixed with N a C l , C a C ^ and M g C b , respectively, at various ionic strengths. This calculation confirmed that the strong chloride salts enhance the activity o f hydrochloric acid. In the same manner, strong solutions o f hydrochloric acid also enhance the activity o f dissolved salts, and even stronger acid solution results i n salting out o f metal chloride salts. This unique thermodynamic  property  o f mixed chloride electrolytes  was  successfully utilized i n the  Falconbridge matte leaching and crystallization processes. Likewise, the salting-out property o f strong hydrochloric acid is used to precipitate other non-associated salts such as FeCl2 and AICI3 as applied in the Pechiney process to recover aluminum from clay. In the present work, calculations were carried out to estimate activity coefficients o f compounds i n the mixture o f M g C L . and HC1. The purpose o f this estimation was to illustrate estimation techniques to compare experimentally obtained values and to apply the calculated values to characterize the leach solutions where measurement is not applicable due to the instrument limitation. T w o techniques, one provided by D i x o n [6], and the second described i n Meissner's papers [31-38] have been utilized. Both o f these are the same, except for different approaches to calculating reduced activity coefficients o f components o f mixed electrolytes. The calculated mean activity coefficients o f HC1 i n mixture o f H C l - M g C l 2 having various ionic strength, are plotted i n Figures 2.11 a, 2.11b and 2.11c at temperatures 25, 35 and 45°C, respectively, against reference data [43] at these ionic strengths and temperatures. A t the same time, activities o f M g C L . i n solution have been calculated. There are only two reference sources to compare calculated values o f MgCL.. One reference was calculated by R o y et al [43] using Pitzer's equation. The second reference for MgCl2 in H C l - M g C b mixture is provided by K h o o etc [49], again calculated using Pitzer's equation. Calculated values o f yno and YM ci2 as g  well as the reference values are summarized i n the Table A 2 . 3 and A 2 . 4 (Appendix 2) for HC1 and M g C h , respectively.  29  A s shown i n these sample calculations, the activity o f the species i n strong brine and hydrochloric mixture can be estimated at any ionic strength and at any temperature. These calculations allow assigning individual ion activities. In addition, these calculated values could be used to characterize the ionic activities o f high ionic strength solutions, where commercial instruments are not applicable.  30  Figure 2.11 a. 2 5 ° C  Calculated ynci of a mixture having I compared with experimental data from E M F measurement at temperatures [43] b. 35°C  Figure 45°C  2.2.3.3 Experimental methods to estimate activity coefficients: E M F measurement  Activity coefficient measurements i n binary electrolyte mixtures o f H C l + M g C l 2 + H 0 have 2  been made by K h o o et al [49] at 25°C up to ionic strength o f 3.0. R o y and his coworkers [43] extended these measurements up to total ionic strength o f 5.0 at temperatures o f 5-45°C. These are the only available activity coefficient data for this system. Both measurements utilized the method o f measuring the Electro Motive Force ( E M F ) o f the cell A without junction: Pt I H  \\HCl - MgCl - H 0\\ Ag I AgCl  UgasMm)  2  (A)  2  The reaction occurring in the cell A is: '  ^^  2 ( g a s )  +  AgCl ^Ag° H^ {S)  is)+  )  Cl-  +  •  aq)  (2.16)  Therefore, the cell potential is defined by Nernst equation as follows: E = E°-2303RT/nF  W  *log  a a  w  h PT*P  (2.17)  2  W  = r r m ,m H+  cr  H  =  cr  Y m m HCl  H+  cr  For mixtures o f multiple electrolytes (e.g. HCI-MCI-MCI2-MCI3): m.m H  cr  =m  HCI  (m  +m  HCI  MCl  + 2m  + 3m  MCh  MCh  ) .  In this case, assumptions are made that these are all strong electrolytes and dissociate completely. Therefore, the following equation can be used for mixtures o f multiple electrolytes.  log,0 W  =  where, m  MCl  lQ  S ' 0 tic! *  HC,  m  (Z  MCl  m  +  2  E MC  +  m  h  is molality o f H C l , N a C l etc, m  MCh  3  E  MC  m  + ~) etC  h  (2.1 8)  is molality o f M g C h , C a C k etc and m  MCh  is  molality o f AICI3 etc. For specific case, the activity coefficient o f H C l i n the mixture o f H C l - M g C l 2 is calculated based on the measured potential o f the cell-A: logic YHCI = " I / 2 [ ( £ -E°)/k where, y  HCl  + l o g m {m 10  HCl  HCl  + 2m  MgCh  )],k = 2303RTIF  (2.19)  is activity coefficient o f the hydrochloric acid  E - cell potential (corrected by hydrogen pressure and liquid junction potential) E°-reference electrode standard potential (varies with temperature)  32  m , HCl  m  -molal  MgCl2  concentrations  o f hydrochloric acid  and magnesium chloride,  respectively. The next approach o f measuring cell potential was to use commercial reference electrodes instead o f the hydrogen electrode and adjust the potential by applying junction potential. This measurement approach has been discussed i n M u i r and Senanayake's work for determining junction potential [29]. In this work, combination o f S C E and hydrogen electrodes were used for hydrogen ion activity measurement, whilst S C E (with junction) and A g C l pasted A g electrode (no junction) was used for CI" ion activity measurements. They proved that the Henderson equation, which is applicable to define junction potential, is valid up to ionic strength o f six. Beyond this ionic strength, this equation is not applicable [29]. The next approach to measure activity coefficient i n chloride mixture had been carried out by J i [19] at the University o f British Columbia. Commercial p H glass electrode was chosen for the purpose o f measurement. J i made p H measurement based on the following approximate principles. pH = - l o g  1 0  a  H+  =-log  1 0  ym +  +  « -log, y C 0  +  H+  (  2  2  0  )  Concentrated hydrochloric acid solution was added into a known concentration o f NiCl2 aqueous solution whose p H changes are measured constantly. Then a plot o f aH+ vs m(Hci)  added  was  constructed for each N1CI2 concentration. The results show almost straight lines, whose reverse slope indicates the activity coefficient o f that solution.  c„.=c, c =«„./,„, =10-"+  0  <-» 2  2  The liquid junction potential o f the glass electrode was determined and i n this way the true p H values were obtained. Because o f its simplicity, the E M F measurement with no junction w i l l be tested i n this work.  33  2.2.4  Corresponding water activity or osmotic coefficient  2.2.4.1 Expressions for water activity and osmotic coefficient  K n o w i n g mean ionic activities for an aqueous solution, the chemical potential p.; can be calculated using equation 2.6. Then the corresponding water activity may be obtained by solving the Gibbs-Duhem relation:  ]£>M=0  (2-22)  or it can be written as:  1000/18dlnfl + X[v // rfln( )] = 0 w  /  /  W  (  2 2  3  )  Further, for an aqueous solution o f single electrolyte, it is simplified as: 1000 /18d In a + m vd Ma.) = 0 A  W  A  V ±>  (  2 2  4  )  For 1:1 electrolyte, the corresponding water activity (a° ) may be directly read from Meissner w  chart, whereas, it can be calculated as follows for non 1:1 electrolyte.  log (^) = 0.0156/(l-l/z z_) + l o g K ' ) 1 0  +  1 0  ( - ) 2  2 5  For a mixture o f electrolytes, the corresponding water activity is calculated as follows [6]:  log.o a = YL v W  w  l  Q  g i o + r  r = 0 . 0 1 5 6 [ / X 2 X / , . / . /(Z/„)-£/,.  (2-26), where  Iz) - I / , / z j ] (2-27) and  34  In addition to water activity described here, the related quantity, the osmotic coefficient § is defined as follows: ^ ^ = -55.511na /2 v,.7w . w  J  (2-29)  (  Generally, this equation defines the osmotic coefficients for pure electrolytes at 25°C. M o r e meaningful <>| value for mixed electrolytes at elevated temperatures can be determined from the activity coefficient data (equation 2.22) as described i n Jansz [7].  X Jf  m  1  <p = \ + 2>« «  £  v,w,. In y. -  w  i  rM  v  (2.30)  The integral part o f this equation may be graphically evaluated more conveniently.  2.2.4.2 Estimating osmotic coefficients o f H C l and M g C l  To illustrate validity o f equation  2  2.30, and further to use it for mixed electrolytes, the  osmotic coefficient calculation has been carried out for pure H C l and M g C l  2  electrolytes,  separately. (Figure 2.12a and 2.12b, and Figure 2.13a and 2.13b)  Figure 2.12  Calculated activity coefficient vs. reference data [42] at 2 5 ° C for single electrolytes a) H C l  b) M g C l  11111  3  1.8  o  1.4  ref 142]  2.2  •cal c  1  1 1 11 A  ref[42]  <> - 1.4  0  Mi  DC  £0.6  i  s  •3 0.2  «a 0.6  -0.2  -0.2  -0.6 -1  2  A  -1 2 m  4 HCl  2 m  4 MgCI2  35  The calculated mean ionic activity coefficient data compared with reference data show an excellent agreement for HC1, while M g C b data is a little bit off, but it can still be used for further calculation. The curves on Figure 2.12 are graphically integrated. In consequence, osmotic coefficients for HC1 and M g C h are evaluated. This calculated data shows an excellent agreement with reference data compiled by Robinson & Stokes [42] as shown i n Figure 2.13a and 2.13b. Those calculated and reference values are summarized i n table A 2 . 2 i n the Appendix 2. Figure 2.13  Calculated osmotic coefficients vs. reference data [42] at 2 5 ° C for single  electolytes a) HC1  b) M g C l  2  The calculated mean ionic activity coefficients for pure electrolytes o f HC1 and M g C b . are compiled i n Table 2.6a and 2.7a, respectively.  2.2.5  2.2.5.1  Individual ionic activities  Individual ionic activities i n single/mixed electrolytes There is no direct method to calculate the individual ionic activities. However, they may be  estimated by a number o f different methods. The most reliable methods are acidity functions (Ho), E M F measurement, hydration treatment and the Ferrocence methods [29]. From these, the E M F measurement method stands out as the fastest and most convenient. E M F measurement i n  36  appropriate cell while knowing the liquid-junction potential has been applied to determine the activity o f hydrochloric acid. Determining the junction potential o f cell is the difficult part o f this method [28]. Stokes and Robinson [42] proposed an expression for mean ionic coefficients for unassociated strong electrolytes as follows:  lny  = [z z~ ] In f -hlv  In a - l n [ l + 0.01 S(v-h)m]  +  ±  DH  (2.31)  w  where,//)//- is the electrostatic contribution expressed as an activity coefficient.  /  = -Al ' 1(1 0 5  + Ba°I ) 05  can be estimated by Debye-Huckel theory giving correct values for the  activity coefficient o f hydrated ions on the mole fraction scale, h-hydration number (the number o f moles o f water bound to one mole o f solute). Values o f hydration numbers are provided for some electrolytes and specific molality i n Table 2.3.  Table 2. 3  Hydration numbers of some simple salts and ions [28] Salt  m  h  HC1 NaCl  0  8 3.4  1  4.6  2  3.8  5.1  3.2  1  4.1  0  12  KC1 CaCl  MgCl  2  2  1  8.2  2  6.9  4.1  5  0  13.7  1  7.8  2.1 4.2  7.4 5.9  h. 7 5  1±1 1±1  12  1±1  14  1±1  This approach is based on the fixed hydration number independent o f concentration. In concentrated solution, especially for highly hydrated salts, where a large number o f water bound to ions i n solution, the calculated activity coefficient may have misleading results. To overcome this problem, Jansz brought up an empirical equation for an "average hydration number" as a function of fixed hydration number and the activity.  37  log,,, h = l o g h + (5 l o g a 10  0  10  w  (2.32)  This equation is valid for water activity o f 0.4-0.9, where log-log plot o f calculated hydration number against water activity shows linear relation. Jansz provided experimental values for ho and P for H C l and M g C l (Table 2.4). 2  Table 2. 4  Hydration number at infinite dilution (ho) and P values [7] HCl MgCl  2  ho  P  6.4 12  0.51 0.36  U p to this point, we have defined mean ionic activity o f a compound, hydration number and osmotic coefficients, which are the main parameters to estimate single ion activities. Bates et al. stated expressions for separating mean salt activities into the contributions o f individual ionic species by extending hydration theory. For univalent salts (MCI):  log V  = S i o Y± + O.OO782A/H0  log 7 10  (2.33a)  l o  10  = log  CR  10  Y - 0.00782/zm^  ( 2  ±  3 3 b  )  For unassociated s a l t s - M C ^ : l°gio 7 > = 2 l o g y + 0 . 0 0 7 8 2 / ^ + l o g [ l + 0.018(3 - h)m] I0  log y 1 0  c r  ±  =log ^ +0.00782/z/T2^-log[l + 0.018(3 - 4 ) w ] 10  ^  10  ±  (2.34b)  Further Robinson and Bates expressions can be extended to calculate single-ion activity coefficients for two 1-1 electrolytes, A and B at constant ionic strength were used:  logio 7  = r log f  CR  A  10  A  + Y log.o YB - 0 . 0 0 7 8 2 / ^  log.o Y , = 2 l o g YA ~ l o g H  10  (  2  3  5  a  )  B  10  Y  CR  (2.35b)  For mixture o f 1-1 and 1-2 electrolytes: (this is important i n view o f the possible use o f H C l / M g C b solutions for the leaching o f sulfides.)  38  (THO + YMtp,.) gio 7 2  lQ  = THCI 8 . O f 1o  cr  Ha  YHCI l o g [ l + 0-018(2- ^ 10  l o g [ l + 0.018{(2 - h )m  a  10  HCl  HCl  ) m „  a  + r c, log r ^ a , " 0 . 0 0 7 8 2 ^ ^ * ^ / 2 + y ^ h ^ 13)(2m Mg  2  I0  ] - 2 ^ l o g [ l + 0.018(3 - h 10  + (3 - h  MgCl2  )m  + 3m , )  HCI  MgCl2  )m  MgCh  MgC 2  ]+  }]  MgCh  (2.36a)  The H activity coefficient is calculated as follows: +  log y^=21ogy*-logy 10  (  2  3  6  b  )  cr  Note that all parameters in single ionic activity calculation equations y±, h, (j) are not fixed numbers, they all are variables as a function o f concentration. Keeping this i n mind, it is now possible to estimate single ion activities i n a pure electrolyte and as well as for the mixed electrolytes.  2.2.5.2 Estimation o f individual ionic activities and p H o f a mixture  Activities o f H and CI" ions are calculated using equation 2.33a and 2.33b for solutions o f +  l - 6 m HC1 at various temperatures. These results are summarized i n Table 2.8. Individual ionic activities o f M g  2 +  and CI" are calculated using equation 2.34a and 2.34b for aqueous solutions o f  M g C l 2 i n relation to molality and temperature, as well. The results are shown i n Table 2.9. A s mentioned before the interest o f hydrometallurgist is generally not i n pure electrolytes. The mixture o f electrolytes is much more interesting. Therefore, individual ionic activities are calculated for mixtures o f HC1 and M g C b at various ionic strength and temperature using equation 2.36a and 2.36b. The results are summarized i n table 2.7 at 25°C. More results o f this calculation at higher temperatures are compiled i n Tables A 2 . 5 and A 2 . 6 (Appendix 2) at temperatures o f 60 and 100°C, respectively. The highlighted rows i n these tables are the mixtures that m a y b e used in the leaching experiments o f this work. Note that the osmotic coefficient for mixture electrolytes are evaluated using equation 2.30 finding the area (the integral part) under the curve o f respective species on lny .(j mixture) vs. molality diagram. Water activity o f mixture is calculated as described +  in equation  n  2.26. Based on this water activity value, the corresponding hydration numbers were  39  calculated. Using this approach, the individual ion activities o f the mixture can be evaluated. For the osmotic coefficient calculation using equation 2.24, the integral part was calculated as follows; it was assumed that logy o f either H C l or M g C l  obey the Harned equation. The general form o f  2  the Harned equation [53] is shown below.  l o  g  where,  7net =  1 0  y  MgCl  log r°Ho  - ifyM a a  S  2  (2.37)  - Pfrlgck  represents the ionic strength fraction o f the magnesium chloride in the mixture.  A comparison has been made i n terms o f hydrogen ion activity for the pure electrolyte versus mixture electrolytes as shown below. Table 2. 5  Calculated hydrogen ion activity based on individual ion calculations M  m  HCl  MRCI2  1  0 0.87  --  2  3 7.87  4  13.15  6621  • -  These results confirm that the hydrogen ion activity i n l m H C l increases 9 times with the addition o f 3m M g C l . This would yield p H o f -0.9 (pH=0.06 at V  =0.87) at only l m  2  o f acid concentration. This shows the potential to develop high leaching power i n mixed electrolytes. A s seen here, the calculation o f the individual ion activity coefficient determines p H o f a mixture. Note that the individual ion activities are calculated based on the mean ion activity coefficients as described i n section 2.2.3.1. For the mean activity coefficient calculations, two approaches were tested. One was described i n Meissner's papers, and the second was the modified method by D i x o n for mixed electrolytes. The results by both approaches differ slightly as shown in Figure 2.11. Therefore, p H values were calculated for one set o f data (I tai 5 at 25°C i n Figure =  to  2.11) and results are summarized i n Table 2.6. There is not a big difference between p H values based on both approaches; hence one o f these approaches w i l l be utilized further to characterize solution properties. Table 2. 6  Comparison of p H values based on the two different approaches m ci  Calculated p H m  MgC12  I total  Meisner  5.00  0.00  5.00  Dixon -1.30  3.58  0.47  5.00  -0.90  -1.02  2.40  0.87  5.00  -0.65  -0.71  H  -1.31  1.77  1.08  5.00  -0.46  -0.49  0.86  1.38  5.00  -0.04  -0.05  40  The p H values for the mixtures highlighted i n Table 2.10 and ,in Tables A 2 . 5 - A 2 . 6 (Appendix 2) were calculated and summarized i n Table 2.7. The similar mixtures w i l l be used for the experiments o f this work. There are no commercial electrodes to measure the p H o f these strong acid solutions; therefore, calculated p H values are applicable to characterize solution properties when measurement is limited. Table 2. 7  Estimated p H of solution mixtures at temperatures pH at temperatures mHci  2.00 4.00 6.00 7.00 8.00 10.00 . 6.00 6.00 8.00  m  MgCI2  2.00 2.00 2.00 2.00 2.00 2.00 2.30 2.40 2.40  25°C -1.05 -1.92 -2.62 -2.94 -3.23 -3.77 -2.74 -2.78 -3.36  60°C -0.78 -1.57 -2.18 -2.46 -2.71 -3.17 -2.29 -2.32 -2.83  100°C -0.53 -1.23 -1.76 -2.00 -2.21 -2.61 -1.86 -1.89 -2.33  41  Table 2. 8  m  HCl  3w  1.0 2.0 3.0 4.0 5.0 6.0  0.970 0.910 0.850 0.800 0.720 0.600  u n  25°C  MgC12  3w  6.301 6.099 5.891 5.712 5.413 4.932  h  M g C 1 2  1.024 1.185 1.360 1.532 1.717 1.920  Yci0.693 0.753 0.839 0.932 1.056 1.249  50°C  60°C  70°C  80°C  90°C  100°C  YH+  Yci-  YH+  Yci-  YH+  Yci-  YH+  Yci-  YH+  Yci-  YH+  Yci-  YH+  Yci-  YH+  0.874 1.267 1.993 3.288 5.630 9.667  0.684 0.726 0.785 0.845 0.924 1.051  0.863 1.221 1.865 2.979 4.922 8.136  0.678 0.708 0.752 0.792 0.847 0.941  0.855 1.192 1.786 2.794 4.514 7.285  0.672 0.691 0.720 0.745 0.779 0.846  0.848 1.163 1.712 2.626 4.152 6.549  0.666 0.675 0.691 0.701 0.719 0.764  0.840 1.135 1.642 2.472 3.830 5.912  0.660 0.659 0.664 0.661 0.665 0.693  0.833 1.109 1.577 2.332 3.544 5.360  0.654 0.644 0.638 0.625 0.617 0.631  0.825 1.084 1.517 2.205 3.291 4.881  0.649 0.630 0.615 0.593 0.575 0.577  0.818 1.060 1.461 2.091 3.066 4.465  Calculated individual ionic activity coefficients for M g C l in relation to molal concentration and temperature 2  <()  25°C Y Cl-  1.0 2.0 3.0 4.0 5.0  40°C  HCl  Table 2. 9  m  Calculated individual ionic activity coefficients for H C l in relation to molal concentration and temperature  0.929 11.685 1.111 0.835 11.247 1.517 0.705 10.582 2.023 0.620 10.104 2.527 0.524 9.507 3.043  Y Mg2+  0.518 0.541 0.707 3.157 0.885 25.140 0.912 207.07 0.813 1637.4  40°C Y Cl-  Y Mg2+  0.479 0.462 0.619 2.418 0.735 17.345 0.724 130.76 0.623 960.34  50°C Y Cl-  Y Mg2+  0.455 0.418 0.569 2.042 0.654 13.714 0.626 97.766 0.526 685.33  60°C  70°C  Y Cl-  Y Mg2+  Y Cl-  Y Mg2+  0.434 0.525 0.584 0.545 0.448  0.380 1.739 10.964 74.093 496.81  0.415 0.486 0.526 0.478 0.385  0.347 1.495 8.871 56.965 366.17  80°C Y Cl-  Y Mg2+  0.398 0.320 0.453 1.297 0.476 7.269 0.422 44.469 0.333 274.63  90°C Y Cl-  Y Mg2+  0.384 0.424 0.434 0.376 0.291  0.297 1.138 6.037 35.278 209.78  100°C Y Cl-  Y Mg2+  0.371 0.277 0.400 1.009 0.398 5.087 0.338 28.464 0.257 163.35  Table 2.10 Calculated individual ion activity coefficients for a mixture of HCl-MgCl2 in relation to molal concentrations of each species at 25°C Dixon m  HCI  m  MgC12  I total  n  MgC12  "  HCI'  yCl-  Meisners, Jansz et al. yH+  yCl-  yH+  TEMPERATURE: 25°C 8.00 5.50 3.94 2.00 1.04 10.00 5.01 4.00 1.28 12.00 10.79 7.68 6.00 3.95 1.37  0.00 0.83 1.35 2.00 2.32 0.00 1.66 2.00 2.91 0.00 0.40 1.44 2.00 2.68 3.54  8.0 8.0 8.0 8.0 8.0 10.0 10.0 10.0 10.0 12.0 12.0 12.0 12.0 12.0 12.0  0.500 0.518 0.561 0.641 0.691 0.380 0.457 0.491 0.611 0.300 0.303 0.341 0.379 0.443 0.550  9.350 9.473 9.748 10.227 10.504 8.470 9.049 9.287 10.052 7.779 7.804 8.147 8.465 8.950 9.678  4.494 4.578 4.767 5.103 5.300 3.907 4.291 4.451 4.980 3.463 3.479 3.697 3.903 4.225 4.719  1.000 0.923 0.837 0.666 0.541 1.000 0.781 0.702 0.385 1.000 0.981 0.884. 0.796 0.637 0.323  3.775 1.947 1.615 1.516 1.567 6.888 2.335 2.166 2.170 12.074 8.028 4.001 3.205 2.783 2.897  28.673 11.228 8.802 5.488 4.072 96.394 22.914 18.544 8.553 296.804 88.503 73.282 56.711 36.411 16.800  1.022 0.929 0.833 0.640 0.497 1.019 0.790 0.707 0.358 1.033 0.996 0.864 0.757 0.573 0.215  3.628 2.048 1.707 1.581 1.617 6.641 2.477 2.286 2.236 11.537 8.182 4.361 3.512 3.025 3.088  29.834 16.287 10.428 5.652 4.054 99.981 28.282 20.987 8.530 310.597 237.508 109.998 69.950 38.401 16.134  13.00 11.20 9.75 7.00 3.02 1.06 14.00 12.20 10.49 8.00 3.39 2.23 16.00 14.63 11.25 10.00 4.60 3.20 12.90 8.33 6.00 2.95 2.25 13.20 11.98 6.00 3.73 1.89 15.20  0.00 0.60 1.08 2.00 3.33 3.98 0.00 0.60 1.17 2.00 3.54 3.92 0.00 0.46 1.58 2.00 3.80 4.27 0.00 1.52 2.30 3.32 3.55 0.00 0.41 2.40 3.16 3.77 0.00  13.0 13.0 13.0 13.0 13.0 13.0 14.0 14.0 14.0 14.0 14.0 14.0 16.0 16.0 16.0 16.0 16.0 16.0 12.9 12.9 12.9 12.9 12.9 13.2 13.2 13.2 13.2 13.2 15.2  0.280 0.286 0.301 0.351 0.477 0.564 0.240 0.246 0.261 0.300 0.429 0.475 0.200 0.202 0.228 0.245 0.366 0.412 0.280 0.322 0.375 0.478 0.508 0.280 0.281 0.373 0.444 0.518 0.200  7.589 7.647 7.785 8.228 9.191 9.767 7.179 7.240 7.400 7.782 8.850 9.178 6.723 6.752 7.051 7.231 8.354 8.722 7.589 7.979 8.429 9.201 9.403 7.589 7.603 8.416 8.959 9.467 6.723  3.344 3.380 3.467 3.750 4.386 4.781 3.091 3.128 3.227 3.465 4.157 4.378 2.816 2.834 3.013 3.123 3.831 4.073 3.344 3.590 3.880 4.393 4.530 3.344 3.353 3.872 4.230 4.574 2.816  1.000 0.971 0.933 0.813 0.478 0.198 1.000 0.972 0.928 0.827 0.465 0.319 1.000 0.981 0.897 0.849 0.484 0.330 1.000 0.850 0.710 0.421 0.330 1.000 0.979 0.724 0.524 0.292 1.000  15.533 8.754 6.178 3.927 3.148 3.504 20.456 11.587 7.679 4.993 3.628 3.739 33.211 21.475 9.704 7.815 4.760 4.781 15.190 4.808 3.594 3.190 3.253 16.238 10.833 3.653 3.273 3.420 28.196  511.733 141.214 132.639 95.502 38.491 19.824 837.344 213.733 199.253 151.778 57.019 39.847 2208.874 487.828 423.856 371.895 136.748 92.390 483.867 108.893 75.254 35.672 28.642 572.063 154.771 84.259 49.497 28.082 1472.131  1.043 0.984 0.925 0.770 0.381 0.065 1.041 0.985 0.919 0.789 0.368 0.202 1.039 1.000 0.876 0.815 0.388 0.213 1.031 0.856 0.704 0.388 0.287 1.021 0.986 0.677 0.454 0.196 1.028  14.716 9.077 6.659 4.346 3.434 3.763 19.486 12.029 8.325 5.546 3.981 4.070 31.747 21.947 10.745 8.751 . 5.310 5.296 14.530 5.181 3.874 3.374 3.424 15.631 11.094 4.026 3.560 3.665 27.251  540.157 360.537 253.694 124.419 38.045 18.716 879.029 588.716 392.419 210.331 56.480 38.090 2310.718 1715.600 787.759 582.743 138.113 88.622 505.829 170.961 91.712 36.284 28.495 594.282 454.987 99.552 50.686 27.088 1523.199  8.00  2.40  15.2  0.292  7.701  3.414  0.711  5.753  213.189  0.719  6.232  288.545  5.83  3.12  15.2  0.351  8.228  3.750  0.546  4.725  141.570  0.547  5.063  161.939  3.30 2.18  3.97 4.34  15.2 15.2  0.442 0.492  8.946 9.293  4.222 4.455  0.279 0.127  4.485 4.728  73.548 51.060  0.263 0.098  4.720 4.937  74.911 50.557  43  2.2.6  Thermodynamic predictions  a) Dissolution of sulfide minerals The individual ion activity calculations allowed for estimates o f the p H values o f any mixtures as described in the previous section. To select a proper mixture o f H C l and MgCh  to  dissolve certain sulfide minerals, it is useful to predict p H values for each sulfide minerals where dissolution occurs. Based on the Gibbs free energy o f corresponding dissolution reactions, these p H values can be estimated. For example, the dissolution o f millerite is predicted as follows: NiS + 2 H  O  + ( a )  Ni  2 + (  + H S( )  a)  2  at equilibrium, AG°(25°C) =-2.14 kJ/mole  g  (RXN2.1)  Assuming unit activities for solid compounds and 1 arm pressure for gas phases, and assigning a unit activity for the dissolved metal cations (a „ Me  t  = l ) t h e solution p H relates to the  Gibbs free energy as follows: H  (  a  i  =  A G )  =  °( ) J  where m is the number o f moles o f the hydrogen ion involved i n the sulfide mineral dissolution. In this specific example m=2. Applying the same principle, p H values for the selected minerals were estimated at different temperatures. The results are summarized i n Table 2.11 and plotted on Figure 2.14. Note that the predicted p H values are calculated at a unit activity o f the dissolved metal cations. It was assumed that at the unit activity o f dissolved metal cations, an acceptable dissolution w i l l occur.  Table 2.11  The AG° and estimated p H values for the dissolution ol ' selected sulfide minerals AG , kJ, at °C 25 60 100 -18.32 -25.70 -28.29 -2.14 -5.17 -6.66 0  Mineral Ni S 3  N i S + 6HCl = 3 N i C l  2(a)  NiS + 2 H C l = N i C l FeS + 2HCl = F e C l  +H S +  3  2  NiS FeS  2  (a)  (a)  (a)  PbS CuFeS FeS 2  Equilibrium Reactions  2(a)  2  2  (g)  + H  (g)  PbS + 2HCl = P b C l + H S CuFeS + 2HCl = CuS +FeCl +H S (a)  2  2(a)  + 2H S  2  2(a)  FeS + 2HC1 = F e C l 2  2  (a)  W  (g)  2(a)  2(a)  +H S 2  fe)  2  +S  (g)  2 ( g )  15.66  5.48  -5.50  20.97 47.58  11.48 37.30  1.65 26.17  72.52  60.94  48.26  pH at equilibrium when a(Me )=l 25 60 100 0.53 0.67 0.66 0.41 0.19 0.47 -1.37 0.38 -0.43 n+  -1.84 -4.17 -6.35  -0.90 -2.92  -0.12 -1.83 -3.38  -4.78  A G data from HSC Version 5.1 0  44  F i g u r e 2.14  Predicted p H for the dissolution of selected minerals  Based on these thermodynamic calculations, the dissolutions o f the selected minerals are summarized as follows: Heazelwoodite and millerite would be expected to dissolve i n acid solutions with low acid concentration i n the p H range o f 0.0-0.5. Troilite and galena would be directly attacked in strong acid. In both cases, increasing temperature up to 100°C has a beneficial effect to increase the dissolution p H o f the minerals. Unlike these minerals, chalcopyrite dissolution requires a significant amount o f acid addition to be dissolved. However, higher temperature increases the required p H up to around -2.0. According to Table 2.7, the mixture o f 7m HC1 and 2m M g C l w i l l have -2.0 o f p H 2  value. A m o n g the sulfide minerals considered here, pyrite would be expected to have the most refractory behavior in the direct attack o f acid. The mixture o f 10m HC1 and 2m MgCl2 has a p H o f about -2.76 (Table 2.7); therefore creating a solution with p H o f about -3.5 (at 100°C) to dissolve pyrite may not be practical. The previous section estimated the p H values o f any mixtures. This section predicted the p H values where certain minerals could be dissolved. Combinations o f these predictions allow selecting a suitable mixture o f HC1 and MgCl2 to process certain minerals and commercial concentrates.  45  b) Chemistry of dissolution products  Let us revisit the prediction o f sulfide minerals dissolution (Table 2.11). In strong acid solution, the sulfide minerals o f common base metals dissolve forming H2S gas i n addition to their corresponding metal chloride salts. The H2S gas is a strong reducing agent (as well as H2 gas i n case of heazelwoodite dissolution). A n interesting question is how w i l l H2S gas react with the metal cations i n solution. It is especially a concern, as illustrated below, i f the solution contains ferric and cupric ions. Cupric and ferric reduction by H2S gas is favorable i n terms o f Gibbs free energy.  C u C l a ) + H S ) = CuS + 2 H C l 2(  2  (g  2FeCl + 3H S 3  2  ( g )  ( a )  = 2FeS + S° + 6 H C l  ( a )  AG°(25°C) = -84.68 kJ/mol  ( R X N 2.2)  AG°(25°C) = -202.9 kJ/mol  ( R X N 2.3)  The solid products formed by these reactions (especially elemental sulfur and copper sulfide) may have a deleterious effect on the leaching o f minerals due to the formation o f passive layers. Furthermore, i f the feed contains copper, its extraction into solution w i l l always be lower than the other metals since the dissolved copper more likely precipitates according to the above reaction ( R X N 2.2). If feed contains both heazelwoodite and copper minerals, copper extraction w i l l be much lower than nickel since both H S and H2 gases reduce dissolved copper. The reduction o f cupric ion 2  by H2 gas is also very favorable compared to other cations as illustrated by the following reactions.  C u C l a ) + H ( ) =Cu+ 2 H C l 2(  2  g  ( a )  AG°(25°C) = -61.4 kJ/mol  ( R X N 2.4)  FeCl a) + H g ) = Fe+ 2 H C l  ( a )  AG°(25°C) = +52.98 kJ/mol ( R X N 2.5)  NiCl ) + H  ( a )  AG°(25°C) = +54 kJ/mol  2(  2 ( a  2(  2 ( g  ) = Ni+ 2 H C l  ( R X N 2.6)  Although these predictions were made at 25 °C, we expect the same results at higher temperatures; therefore, for the processing o f mixed metal sulfides, the addition or presence o f cupric or ferric ions may have a negative impact on metal extraction.  46  2.2.7  Chloride complexes The chloride system presents many important features o f relevance to the hydrometallurgist  in addition to increased ionic activities. One o f these is the formation o f chloride complexes with the common metal cations. This feature allows formation o f ionic species that are not present i n other media such as in sulfate. A good example o f this is the stabilization o f cuprous chloride complexes along with cupric chloride. The combination o f these ions can create a strong leaching environment to effectively leach sulfide minerals, while allowing copper metal to be recovered from its lower valence state. There are several observed phenomena for the chloride complex system. First, this type o f complexation is weaker than the aquo complexes. Second, the metal cations that are complexed poorly by water, form strong chloride complexes. Table 2.12 summarizes a general categorization o f metals according to their tendency o f chloride complex formation.  Table 2.12  Strengths of chloro-complexes according to periodicity [28] WEAK  Lanthanides  LogK<l  Actinides Transition metals Groups III-VIII  ( N i < Fe < Co  Group IV  ( Sn  Group VIII  (Fe )  Coinage metals  (Cu <Ag <Au )  Volatile metals  (Zn  Precious metals  (Os  Group V  (As  2 +  2 +  <Cu )  2 +  2 +  Moderate 1 < logK < 3  < Pb  2+  )  2+  2 +  Strong LogK >3  +  2 +  3 +  3 +  +  < Cd «Ir «  3 +  2 +  3 +  «  «Pd  Sb  3+  Hg ) 2 +  2 +  ,Pt  2 +  ,Pt  4 +  )  < Bi ) 3 +  The transition metals i n the second row form stronger chloride complexes than the first row metals, especially i f in their lower valence state. In addition to general rules for metals, chloride complex formation is also strongly related to chloride ion concentration. Table 2.13 summarizes the chloride complexes o f common metal cations that may be present i n the solution o f sulfide concentrate leaching.  47  Table 2.13  Resume of the common chloro-complexes [6] Low C l - concentration  High C l - concentration  Cu(II)  Cu  CuCl  Cu(I)  CuCl '  Fe(III)  Fe -  Fe(II)  Fe  Zn  Zn  ZnCf  Pb  PbCf  PbCl  Ni  Ni  Co  Co  Mn  Mn  Cd  Cd  Sb  SbCl  Bi  BiCl  CuCf  2 +  CuCl "  2  3  CuCl "  3  3  4  FeCl  3+  2  4  CuCl "  2  2  CuCl "  FeCl  2+  + 2  FeCf  2+  ZnCl  ZnCl "  2  3  PbCl "  2  ZnCl " 2  4  PbCl " 2  3  4  NiCl  2 +  +  CoCf  2 +  MnCf  2 +  CdCl  3 +  SbCl  2+  BiCl  2 +  +  CdCl SbCl  + 2  BiCl  + 2  3  3  As  CdCV  CdCl "  SbCl "  SbCl -  SbCl "  BiCl "  BiCl "  BiCl "  Ag Hg  HgCl  2  4  5  2  4  AsCl Agcr  2  5  2  4  3  6  3  6  3  AgCl " 2  3  HgCl  +  HgCl -  2  3  HgCl " 2  4  In general, the complexation is represented by the following reaction. Me" + iCl <^> MeCir  (2.38)  +  The maximum ligand number-i is often four i n chloride system. The corresponding stepwise stability constants are defined as: K  0  (2.39)  MeCir  a =  The cumulative stability constant is: (2.40)  The complexation changes free energy o f a metal ion as written below, which i n turn changes its reduction potential.  AG  0 com  p,ex = AG° tai - 2 . 3 0 3 R T L o g Pi me  (2.41)  Therefore, the effect o f complexation on the reduction potential can be observed by the Nersnt equation (e.g. for reaction 2.38).  48  2303RT F =F * Me"* I Me"  „, A 0_i fli cr *log  (2.42)  MeCir  The increase i n background [Cl"] generally decreases E h for metal ion/metal complexes depending on the Pi and complexing number-n. Considering the effects o f complexation on the reduction potential, M u i r and co-workers constructed the Eh-p[Cl"] diagram for various base metals (Figure 2.15).  Figure 2.15  Eh-log[Cl] diagram at 2 5 ° C [28]  (Calculated using p„ assuming y = 1; Pb(II) and Bi(III) = 10" M , Ag(I) and Au(III) = 10" M , others 10" M , p H = 1)  4  5  This  diagram  1  provides  useful  thermodynamic  information o f chloride complex species and their region o f stability. It is known that the metals with lower E h i n this diagram can displace (cement out) metals with higher E h from their solutions. It is detrimental i f impurities are cemented on to the final  metal  product,  but  advantageous  in  the  solution purification and recovery o f some metals from their chloride solutions.  log[Cn  49  2.2.8  Solubility of chloride salts One o f the multiple advantages o f chloride leaching media is an increased solubility o f  metals compared to sulfate media. Solubility data o f metal chlorides that are commonly found in the leaching o f sulfide minerals are compiled extensively i n Linke [47]. Even solubility o f sparingly soluble salts is increased by several orders i n chloride media [3, 7]. A s described in the literature, temperature has a significant effect on the solubility o f chloride salts. Decreasing temperature may allow precipitation o f chloride salts such as A g C l and P b C ^ . Calculations o f individual ion activities in section 2.2.5 confirmed that the mixtures o f chloride salts with hydrochloric acid create high individual ion activities including hydrogen and chloride ion. The addition o f salts that form a high background concentration o f chloride has a significant effect on the solubility. Whilst hydrogen ion breaks the sulfide mineral lattices down forming metal cations, the chloride ions form complexes with these cations increasing their solubility. In addition, it is observed that the solubility limits vary, not only with the total chloride concentrations, but also with the type o f chloride salts added to the solution (or contents o f the commercial product that is processed in strong brine). Table 2.14  AG  0  reaction  of selected chloride complexes at 2 5 ° C , kJ/mole  Complexing reactions C u + nCl" O CuCl,, "" +  Cu Ni  1  2 +  + nCl" <» C u C l " 2  n  n  2 +  + nCl" O N i C l " 2  n  n  Co  2 +  Mg  2 +  Ca  2 +  Fe  2+  Fe  3+  + nCl" »  CoCl " 2  -  2  + nCl" O C a C l " 2  n  n  n (complexing numbers) 2 3  -38.74  -30.24  -32.53  -2.71  23.24  13.08  5.75  49.15  n  0.99 -0.82  + nCl" O FeCl "  0.93  91.53  + nCl" <» FeCl "  n  -8.44  -81.24  n  3  n  26.21  121.77  n  2  4  -119.57  n  n  + nCl O MgCl„ -  1  78.80  Table 2.14 shows the Gibbs free energies for the selected metal cation-chloride complexes that may form i n chloride media during leaching o f sulfide minerals. What is expected from this information? Cuprous, ferric and cobaltous cations have great affinity, whereas cupric and calcium ions have less tendencies to form complexes with chloride ions. Divalent cations such as nickel and magnesium have no tendency to form chloride complexes. These complexation behaviors have positive or negative effects on metal dissolutions. The weak complexation o f magnesium leaves chloride ions free i n solution resulting i n an increased concentration o f this ion (in case o f using the  50  mixture o f M g C l  2  and H O ) . The free chlorides form complexes with the dissolved metal cations  enhancing their solubility. In addition to dissolved metal cations (in this specific case N i , C o , 2 +  2 +  C u ) , i f a solution contains metal cations that form strong chloride complexes such as C u and Z n , 2+  +  2 +  the complexation w i l l have deleterious effect on the solubility o f the weak complexing metals. This phenomenon may easily be illustrated by the following example. Say that a leach solution contains ferric ion i n addition to dissolved copper the following reaction w i l l most likely take place. CuCf + Fe  3 +  + 3C1" => CuCl ( ) + F e C l 2  S  + 2  (a  q)  ( R X N 2.7)  The salts that form strong chloro-complexes depress the solubility o f salts that form weak chloro-complexes. However, CuCl ( ) w i l l not precipitate in dilute solutions as shown here; this may 2  S  retard dissolution kinetics i f the solution is concentrated.  2.2.9  Effect of A1C1 , NaCl and C a C l on activities of M g C l + H C l mixture 3  2  2  A leach system contains a variety o f minerals, metal cations and chemical species; therefore, it is useful to estimate the effects o f each component on the activities o f each species. The effects o f Al  3 +  and N a  +  cations on proton activities were estimated (an interest o f project supporters). In  addition, the effects o f M g  2 +  and C a  2 +  were considered since these metals are encountered i n any  type o f ore and are dissolved in a chloride leach system. The effect M g  i n solution draws a  2 +  particular interest in order to process high magnesium containing feeds i n this mixture. Again, taking the Meissner method as a guide for mixed electrolytes, the activity coefficients o f each salt were estimated assuming they were i n the chloride salt form and dissociated completely. The results are shown i n Figures 2.16a to 2.16d for the case o f increasing concentrations o f single salts (the remaining salt concentrations were kept constant). The effects o f double salts are plotted in Figures A 2 . 1 a to A 2 . 1 d (Appendix 2). Complete results are summarized i n Table A 2 . 7 (Appendix 2). Selected results at higher concentrations are shown i n Table 2.15. A s shown in Table 2.15, AICI3 has the most impact on increased activity coefficient o f HC1. In contrast, N a C l has no advantageous effect on increased HC1 activity coefficient. C a C l has a 2  noticeable effect on it, more importantly M g C l has a higher effect than C a C l . This shows that the 2  2  high clay (high A l ) and M g O content feed mixed with an acid has the potential for creating high acid activities. The activity coefficients o f HC1 i n the presence or absence o f added salts (58 vs. 7, respectively) are presented i n the fifth and last row o f this table. This tells the advantages o f using mixtures instead o f pure acid solution. Rows 6 to 8 o f this table summarized the effects increasing  51  concentrations o f double salts. Increasing molalities o f AICI3 and M g C h up to 4m results i n mean ionic activity o f 88 for HC1 while the rest o f salt ( M g C ^ , N a C l & HC1) molalities are kept at constant o f l m . Double salts o f M g C ^ and.CaCh create HC1 activity coefficient o f 61 (vs. 88 in previous case), which is excellent combination for the purpose o f increased HC1 activity coefficient. Figure 2.16a displays the effect o f increasing AICI3 concentrations on the activity o f HC1 while other salt concentrations remained constant. Each curve on this figure represents the activity coefficient changes o f corresponding salts including HC1. In addition, a total ionic strength is included in this plot. Figures 2.16b-2.16d displays the same information, the only difference is the concentration o f salt, o f which the effect that was considered, is increasing. Figures A2.1a-A2.1d (Appendix 2) contain the same information, in these cases the effects o f double salts were estimated. Overall, more salt addition with increasing concentration results i n increased HC1 activity coefficients in the mixture. Therefore, i n terms o f increased HC1 activity coefficient, the mixture o f HC1 and M g C h is suitable to process high clay (high A l ) and M g O containing materials.  Table 2.15  HC1 1 1 1 1 1 1 1 4  Effect of added salts on calculated HC1 activities at 25°C Molal concentrations of each salt MgCl A1C1 NaCl 1 1 4 1 1 1 1 4 1 4 1 1 1 1 1 4 1 4 4 1 1 4 0 4 0 0 0 2  3  CaCl 1 4 1 1 1 1 4 0 0  I total 2  32 23 17 23 17 41 32 37 4  Activity of HC1 34.81 20.97 10.53 24.48 58.47 88.46 61.12 62.14 7.00  52  Figure 2.16  Effects of A1C1 , NaCl and C a C l on activities of M g C l + H C l mixture 3  2  2  a) The effect o f AICI3  b) The effect o f G a C l  c) The effect o f N a C l  d) The effect o f M g C l  2  2  20  0  1  2  3  4  Molality of NaCl -•-HCl  -D-MgC12  -0-A1C13  -£-CaC12  —O-NaCI 1 total  0  1  2  Molality of M g C l  -•-HCl -0-A1CI3  -D-MgC12 -6-CaC12  3 2  -•-NaCl 1 total  53  2.2.10 Summary of thermodynamic review  Reviewing the thermodynamics o f strong electrolyte mixtures, it is clear that the activity coefficients are important parameters that need to be estimated. A m o n g several  techniques  developed to estimate activity coefficient, the Meissner method is considered the simplest and most convenient to use. In the present work, activity coefficients o f HC1 and M g C l  2  i n the mixture o f  H C l - M g C l 2 - H 2 0 have been calculated utilizing Meissner's method at various total ionic strengths and temperatures at various ionic strength fractions. Available reference data for this mixture is limited to total ionic strength o f five and temperatures o f up to 45°C. This data was obtained from the E M F (Electro Motive Force) measurement method. The E M F measurement method is considered the simplest experimental method and was selected to be tested i n this work. This method allows determining activity coefficients o f HC1 i n a mixture. Based on this, the activity coefficients o f MgCl2 are calculated using very complex equation o f Pitzer with multiple parameters. These parameters are not easily obtained, and are dependant on both ionic strength and temperature; therefore, current work w i l l only focus on HC1 activity coefficients. There is no experimental technique to determine individual ion activity coefficients i n a mixed electrolyte. However, the individual ion activity coefficients can be estimated  using  expressions provided by Stokes, Robinson and Bates. M o r e accurate estimation can be done applying variable hydration numbers, water activities and osmotic coefficients as suggested by Jansz. The individual ion activity allows the assigning o f the p H o f a solution. This calculation followed the mean activity calculations by the Meissner method. T w o different approaches for mean activity coefficient estimation were used; however, both gave almost the same p H values for a mixture. Therefore, only one method was selected for further calculations o f p H . There were no distinct criteria to select one approach over another. The thermodynamic predictions for dissolutions o f sulfide minerals showed that the minerals such as heazelwoodite and millerite can be dissolved in acid solutions with low acid concentrations with pH~+0.5. The decomposition o f troilite and galena by the direct attack o f a strong acid at p H — 1.0, are favorable. In both cases, the increasing temperature o f up to 100°C has a beneficial effect on the increase o f the dissolution p H o f the minerals. Unlike these minerals, chalcopyrite dissolution requires a significant amount  o f acid addition (pH<-2.0) to be dissolved; however, higher  temperature increases the required p H above -2. Pyrite shows the most refractory behavior in the  54  direct attack o f acid. A n increasing temperature has a weak effect to increase the dissolution p H o f this mineral. The chemistry o f dissolution products (H2S and H gases), with the metal cations in solution, 2  was explored here. If solution contains an excess amount o f cupric or ferric ions, these gases would react with these metal cations, and may cause formation o f a protective layer o f C u S or S, which may prevent further mineral dissolution. In addition, solubility and complexation behavior o f chloride mixtures are reviewed here. Both o f them have positive or negative effects on the dissolution o f sulfides depending on the compositions o f leach media. A s metals form strong complexes with chlorides, their solubility increases. The complexation mostly decreases the reduction potential o f common base metals. The metals with lower potential on the E h - L o g ( C f ) diagram tend to cement out the metals with higher potential. Some cations ( C u , F e ) have a strong tendency to be complexed, while others ( N i , C u ) +  3+  2 +  2 +  have less tendency. The metals that form strong complexes with chlorides tend to precipitate the metals that form weak chloro-complexes. A l l these could lead to lower metal extractions and/or slower leaching kinetics. These may be deleterious effects o f the complexation on the leaching o f some metals such as N i , C o and C u , which are the objectives o f this investigation. The present review established the fundamentals  o f studying thermodynamics o f these  mixtures. The review calculations also provided several important points relevant to the processing of base metal sulfides i n this mixture; furthermore, this review suggested studying o f the leaching chemistries o f individual minerals and commercial sulfide products i n this mixture. M a n y useful leaching parameters, such as leaching time, temperature, and acid concentrations, w i l l be explored i n this work.  55  C H A P T E R 3 EXPERIMENTAL ASPECTS  The experimental program o f this work covered the following two areas: 1. Thermodynamic measurement i n the mixture o f H C l and M g C l  2.  .  Measurement o f H C l activity coefficient  .  Measurement o f M g C l solubility i n H C l solution 2  Study o f leaching chemistry o f individual sulfide minerals and the concentrates i n the mixture o f H C l and M g C l  3.1  2  2  Experimental procedures and methods The first objective o f the experimental part was to measure the E M F o f the cell o f interest.  The experimental procedure o f the E M F measurement method is summarized i n A3.1 (Appendix 3). This experimental technique allows direct and true measurement o f the E M F o f the cell avoiding junction potential; however, the electrodes are not commercially available and need to be prepared as described here. Preparation methods for hydrogen/platinum and silver-silver chloride electrodes were adopted from the work o f Bates [52] and are summarized i n A 3 . 2 and A 3 . 3 , respectively (Appendix 3). The glassware design used for the Harned cell measurement (the cell uses hydrogen electrode) is taken from Harned, Bates & Robinson [45-48] and is summarized i n A3.5 (Appendix 3), The experimental method to measure the solubility o f M g C l  i n hydrochloric acid solutions  2  was adopted from Demopoulos et al, [63]. Excess amount o f M g C l  2  was brought in contact with  solution. After adequate stirring, the liquid sample was taken at specific temperatures. The following procedure solved the initial difficulty o f solid re-crystallization on sampling. A fritted glass tube was inserted into the system deep enough to be at the same temperature as that o f the solution. A t a certain sampling temperature, the vacuum applied to the fritted glass tube allows for collecting clear solution inside the tube, from where sample was taken and diluted for further analysis. Beforehand, both the fritted glass tube and pipette were kept in an oven at certain temperatures in order to eliminate salt re-crystallization due to temperature changes. In each leaching test, a certain amount o f either individual mineral or a concentrate sample charge was leached i n 150 or 500 m l solutions o f mixture. The acid concentration varies, whereas MgCl  2  was kept at 2m. Literature [64] suggests that a minimum o f 200g/l total chloride is required  for the processing o f sulfide minerals i n this mixture. Initial tests o f this work confirmed that increased total chloride concentration has no effect on dissolution. Therefore, through the leaching  56  tests 2-2.4m o f M g C l was added to insure enough chloride i n the solution. Solution samples were 2  withdrawn at specific time intervals, weighed, and converted to volume scale assuming no density change due to the dissolved metals. Samples were diluted and prepared for analysis. A t the end o f leaching, solids and liquids were separated by a vacuum filter, and solids were washed with D I water. Solution volumes and solid weights were recorded and sent for analysis. Selected solid residues were subjected to X R D and S E M - E D X . A n assay o f M g C l stock solution was determined by E D T A titration method as described i n 2  attachment A 3 . 4 . A n assay o f HC1 stock solution was determined by potentiometric titration as illustrated i n attachment  A 3 . 6 . Free acid concentrations o f leach and wash solutions were  determined by a method described i n Wassink [65]. This method is most suitable for acidic solutions with an excess amount o f hydrolysable cations.  3.2  Experimental instruments and set-up The  experimental set-up is similar to the setup shown i n Figure 3.1, however minor  modifications have been made from test to test. Figure 3.1  1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12.  Experimental equipment set-up  Reaction vessel Stirrer P t / H electrode A g / A g C l reference electrode Thermosensor Fritted glass tube for sampling Condenser Hydroseal to prevent air entrance Glass lid with standard openings Barometer Temperature controller o f heating equipment Water bath or heating mantle 2  57  Figure 3. 2  Experimental set-up for thermodynamic measurement  Figure 3. 3  Experimental set-up for leaching test  Leaching tests at lower temperatures (60°C) were carried out in a controlled temperature orbital shaker, which is shown on the far left o f Figure 3.3.  58  A voltmeter, with precision o f O . l m V (Denver Instrument p H / m V ) , was used to measure cell potential for the thermodynamic measurements. A number o f reference electrodes (single and double junction) were used to substitute A g / A g C l reference electrodes. The commercial electrodes were supplied from Thermoelectron. Scientific Glassware C o Ltd., Richmond, B C made the bases o f the Pt/H2 and A g / A g C l electrodes, glass feature, and the 250ml reaction vessel with five standard openings according to specifications and drawings. Pt bases for hydrogen electrodes are platinum-blacked before use. Pt wire base for A g / A g C l electrode was coated with A g first, and then coated by A g C l . For the fhermoelectrical  coating purposes Harrison 6203B B C power supplier by Hewlett Packard  instrument was used. Due to complication o f this method, the latest measurements were made using A g / A g C l bases o f the used p H electrodes. For the initial leaching tests, mineral samples o f pyrite, millerite, pentlandite, violarite, heazelwoodite, troilite and chalcopyrite were sized to minus 200 mesh and leached i n 250ml-baffled flasks with continuous shaking. S / L ratio was kept 1/150 during the tests, neglecting the amount o f liquid samples withdrawn for sampling. The temperature control and continuous stirring was provided by Environ-Shaker by Lab-Line Instrument Inc. The equipment shaking speed was kept i n the range o f 220-240 rpm. For those shaking tests, the system was kept closed to minimize evaporation losses. Solution samples were withdrawn inserting Teflon tubes through a rubber stopper. Tests at higher temperatures (concentrate samples and some minerals) were carried out in a one-liter reaction vessel sitting on a heating mantle. A n overhead-plastic stirrer was used to aid in enhanced mass-heat transfer and to prevent solution contamination. The stirrer was inserted through a septum stopper into the reaction vessel. The contacting areas o f the stirrer rod and septum, and any other joints o f glassware were greased by silica o i l i n order to prevent air entrance into solution and acid losses into surroundings. Double condensers (stacked) were used to minimize evaporation losses. Samples were withdrawn via Teflon tubes using a syringe. The temperature sensor connected to D M C type Dataplate 520 temperature controller controlled power input o f the heating mantle. The water bath temperature was regulated by its own controller. The actual temperature o f the leach system was controlled by DigiSense thermometer.  3.3  Chemicals, minerals and concentrate samples Hydrochloric acid o f analytical grade supplied by Fisher was used as a stock solution for an  acid supply. The concentration o f the stock acid solution was determined by repeated potentiometric  59  base titrations and the end point was defined as shown i n example A 3 . 6 (Appendix 3). Stock solution o f magnesium chloride was prepared by dissolving an analytical grade salt supplied by also Fisher, and the concentration was determined by E D T A titration. Densities o f stock solutions were measured to enable preparation o f mixture o f solutions at exact ionic strength fractions (YM ci2 and g  Y  H C  i ) o f M g C l a n d HC1. 2  C u C l and F e C ^ solutions were prepared by weight percent from reagent grade o f respective 2  salts supplied by Fisher. In addition, 0.1N N a O H , 0.1N HC1 and 0.1N AgNC>3 standard solutions were supplied by Fisher. A reagent grade H P t C l 6 * 6 H 0 (dihydrogen hexachloroplatinate-IV 2  2  hexahydrate) supplied by A l f a Aesar was used for Pt-black purpose. 0.05M E D T A standard solution was bought from LabChem Inc. A l l individual mineral samples, except pyrite, were bought from Mineralogical Research Co., San Diego, U S A . Crystal fragments o f each mineral sample were dry ground i n a laboratory m i l l . M i n o r inclusion o f pentlandite in very rich chalcopyrite sample was removed by hand after crushing mineral particles i n a laboratory cone crusher. The nickel concentrate samples with low (two identical samples) and high (two identical samples) M g O content were supplied from B H P Billiton as well as matte samples (four identical samples) from its Kalgoorlie smelter. Only three representative samples out o f a total o f eight were tested. These are indexed as 1 B H P ( I B ) , 3 B H P (3B) and 5 B H P (5B) throughout the test work. A l l commercial samples were dried. N o further sample preparation was required for concentrate samples i n terms o f particle size. In contrast, a matte sample was re-ground i n powderizing m i l l to pass P80 -200 um prior to leaching. Mineral characterization involved ICP for 30 elements, A A for common base metals and L E C O for total sulfur. International Plasma Laboratory in Vancouver performed all analyses. Some o f sample characteristics are summarized i n Table 3.1. Trace elements are excluded i n this table. Table 3.1 Mineral samples Pentlandite Troilite Millerite Heazelwoodite Violarite Chalcopyrite Pyrite  Summary of mineral and concentrate samples Sample character Test ID Origin Sudbury, Ontario P T Alta Mine, Del Norte County, California M McCreedy West Mine, Levack, Ontario H Lord Brassey Nickel, Tasmania, Australia V Perseverance Mine, Agnew. WA, Australia C Frood Mine, Sudbury, Ontaria, Canada P Unknown  S(tot) 30,41 34,59 32,81 4,50 33,39 33,29 54,06  Co 0,10 0,05 0,24 0,30 0,32 0,00 0,06  Assay, % Cu Fe Mg Ni Si02 MgO 3,22 63,01 0,01 4,07 -8,68 57,23 0,41 0,27 -0,52 13,78 0,03 59,29 0,14 15,12 17,04 10,48 0,43 36,90 0,33 19,03 23,78 35,30 33,75 0,01 0,28 1,31 0,04 49,96 0,01 0,01 —  —  -  Concentrate samples Low MgO concentrate 1BHP(1B) WMC Resources, BHP Billiton, Australia 29,92 0,28 0,32 38,49 4,55 13,50 High MgO concentrate 3BHP (3B) WMC Resources, BHP Billiton, Australia 20,23 0,68 0,12 21,19 9,33 25,75 Matte 5BHP (5B) Kalgoorlie Smelter, BHP Billiton, Australia 24,74 1,02 2,33 5,48 0,03 74,20 -— not analyzed 60  --  8,76 17,4 --  3.4  Solution preparation  Each o f the stock solutions, o f which concentrations and densities were previously determined, were weighed to prepare solutions for the thermodynamic measurement and leaching tests. Solutions for the activity coefficient measurement were prepared at the exact same ionic strength fractions as per the references. A n example is shown i n the next table. Table 3. 2  m  Solution preparation example for the E M F measurement  HCl  m  2.00 1.74 0.20 1.00 0.48 0.32  MgC12  I total  YHCI  YMgC12  V (HCl)  0.00 0.09 0.60 0.33 0.51 0.56  2.00 2.00 2.00 2.00 2.00 2.00  1.000 0.871 0.100 0.499 0.242 0.159  0.000 0.129 0.900 0.501 0.758 0.841  29.26 25.50 2.93 14.60 7.09 4.66  V (MgCl ) water, ml 2  0.00 2.51 17.58 9.79 14.80 16.42  70.74 71.99 79.49 75.61 78.11 78.92  Sol.V, ml 100 100 100 100 100 100  Table 3.3 illustrates the solution preparation for the leaching tests. The volume o f each compound represents the volume o f each stock solutions required for a total o f 500 m l solution. In both tables (Tables 3.2 and 3.3), m represents the molal concentrations o f each salt, Y represents the ionic strength fractions o f each salt, and V represents the volume o f each stock solution required to prepare the specific volume o f a mixture solution. Table 3. 3 m ci H  4.0  m  Solution preparation example for leaching tests  MgC12 C u C I 2 m  m  FeC13  I total  YHCI  YMgC12  YcuC12  YFeCB  0.02  0.00  120.26 223.56 100.00  V  H C  .  VMgCl2  VcuCl2  ^FeCB  H 0 , ml  0.00  56.18  2  2.4  0.2  0.0  11.8  0.34  0.20  4.0  2.4  0.0  0:2  12.4  0.32  0.19  0.00  0.02  120.26 223.56  0.00  100.00  56.18  6.0  2.4  0.2  0.0  13.7  0.44  0.17  0.01  0.00  180.39 223.56  90.12  0.00  5.93  61  3.5  The basic principles of the S E M - E D X , X R D analyses These analyses were utilized to characterize the solid samples before and after leaching. The  composition tables i n section 4.4 ( X R D , S E M - E D X analyses) were created based on the S E M - E D X results. Note that this method has an accuracy o f ± 5 % . These analyses are operated based on the following principles. For the S E M analysis, the sample o f interest is bombarded by beam o f electrons. The interaction o f the electron beam and the sample produces a series o f electron scatters with different energy level, which are analyzed by a sophisticated microprocessor. The electrons produced are classified as either elastic or inelastic i n terms o f energy level. The inelastic electrons are low energy electrons deflected from the surface o f sample. They mostly have electron energies o f less than 50eV, and give information o f the surface topography and a black and white, three-dimensional image o f the sample. The elastic electrons are any electrons that interact with the primary electron beam to produce a specific energy from the collision and retain most o f its energy. These electrons are categorized as: •  Backscattered electrons-yielding topological, compositional and crystallographical surface information.  •  Absorbed current-which enables the study o f the internal structure o f semi-conductors or (EBIC).  •  Auger electrons-contain elemental and chemical information o f the surface layers.  •  Characteristic X-ray Radiation-yields microanalysis and distribution o f elements o f a given sample. A typical S E M has the ability to analyze a particular sample utilizing any o f the above  mentioned methods. Unfortunately, each type o f analysis considered is an additional peripheral accessory for the S E M . The most common accessory equipped with a S E M is the energy dispersive x-ray detector or E D X (sometimes referred to as E D S ) . This type o f detector allows a user to analyze a samples molecular composition. In an S E M , x-rays are produced by accelerating the primary electron beam with enough current to pass through the sample thereby interacting with the elements inner core electrons. When enough high-velocity electron bombardment contacts the inner most electron shell o f an atom, it forces the orbiting electron to be kicked out. Subsequently, this results in the neighboring outer electrons to move into the vacant inner electron shell. The release o f energy from the escaping  62  electrons from the inner most orbiting shell or core electrons are analyzed and measured based on their classification type. For the X R D analyses, the three-dimensional structure o f non-amorphous materials, such as minerals, is defined by regular, repeating planes o f atoms that form a crystal lattice. When a focused X-ray beam interacts with these planes o f atoms, part o f the beam is transmitted, part is absorbed by the sample, part is refracted and scattered, and part is diffracted. X-rays are diffracted by each mineral differently, depending on what atoms make up the crystal lattice and how these atoms are arranged. A detector detects the X-ray signal; the signal is then processed either by a microprocessor or electronically, converting the signal to a count rate. When an X-ray beam hits a sample and is diffracted, we can measure the distances between the planes o f the atoms mat constitute the sample by applying Bragg's L a w . The Bragg's L a w is nX = 2 d sind  where the integer n is the order o f the  diffracted beam, X is the wavelength o f the incident X-ray beam, d is the distance between adjacent planes o f atoms (the J-spacings), and 9 is the angle o f incidence o f the X-ray beam. Since we know X and we can measured, and can calculate the rf-spacings. The geometry o f an X R D unit is designed to accommodate this measurement. The characteristic set o f d-spacings generated in a typical X-ray scan provides a unique "fingerprint" o f the mineral or minerals present i n the sample. When properly interpreted, by comparison with standard reference patterns and measurements, this "fingerprint" allows for identification o f the material.  63  C H A P T E R 4 R E S U L T S A N D DISCUSSIONS  4.1  Thermodynamic measurement  4.1.1  E M F measurement of the cell M g C l - H C l - H 0 using P t / H - Ag/AgCl electrodes with no junction 2  2  2  Table 4.1 lists the experimental E M F and corrected E M F to l a t m hydrogen pressure for constant ionic strength o f two and at each ionic strength fractions o f magnesium chloride-Y ci2Mg  Activity coefficients o f H C l i n each mixture were calculated using equation 2.19 (or equation reported in Appendix 3). The last column i n Table 4.1 lists the activity coefficients o f H C l determined applying the Harned rule comparing to experimentally determined logynci by least square method. The measured potential is corrected to the hydrogen pressure o f l a t m as follows: E =E +^-where,LE^RTI2F\n[16Qlp ] corr  mws  = RT[160  Hi  P - barometric pressure, p  H 0  (4.1)  - water pressure, and h - depth o f jet i n mm. The water vapor  pressure is taken from thermodynamic reference [54] and attached as A 3 . 7 . Table 4.1  Solution compositions, measured and corrected E M F , calculated activity coefficients for H C l at 25°C m ci  I total  YHCI  2.00 1.74 1.50 1.00 0.48 0.32  2.00 2.00 2.00 2.00 2.00 2.00  1.00 0.87 0.75 0.50 0.24 0.16  H  * **  p  ^ meas  0.1885 0.1942 0.2000 0.2163 0.2404 0.2485  ^ corr.  *log Y HCl  **H.E log y HCI  0.1889 0.1946 0.2004 0.2169 0.2410 0.2491  -0.0167 -0.0255 -0.0318 -0.0627 -0.0856 -0.0552  -0.0186 -0.0272 -0.0354 -0.0521 -0.0693 -0.0748  Calculated activity coefficients based on measured E M F Calculated activity coefficients based on Harned equation  Figure 4.1 presents the log values o f activity coefficients for H C l . The activity coefficientsexperimentally measured, determined by the Harned equation, the references [43] and the calculated values by the Meissner method by both approaches, are plotted i n this figure at temperatures 25, 35 and 45°C. Additional measurements were made at temperatures o f 50 and o f 60°C (intended to make measurements up to 100°C); however, it was difficult to obtain a stable E M F reading above 60°C. The Harned rule has been convenient to express this kind o f series measurements at a constant total ionic strength. It expresses the experimental activity coefficients as a function o f concentration:  64  i°gio YHO = log  rlc, - aJyu c - PJy  2  s  h  MgCll  ( 4  2 )  where YHCI is the activity coefficients o f H C l i n the mixture; YHCI is the activity coefficients o f H C l 0  when it is present in its pure solutions at the same total ionic strength as the mixed solution; a and /? are so called Harned coefficients; and y  MgCl  is the ionic strength fraction o f the magnesium chloride  in the mixture, which is given by: JW» = M a 3m  2  g  '{ Hci + Mgck ) m  2  ()  m  43  Table 4.2 compiled the Harned equation coefficients for each set o f measurement at different temperatures. It is clear from Figure 4.1 the calculated activity coefficients based on the Harned coefficients give better results than the experimentally determined values. One way to cross check validity o f these coefficients is to compare H C l activity coefficient with its pure state at the same total ionic strength. A t I =2.0, YHCI = 1.009 at 2 5 ° C [43], i n our case YHCI = 0.98, which means the Harned values agree with the experimentally obtained values. Table 4. 2  Harned equation coefficients Temp, °C  logY°Hci  25 35 45  -0.0186 -0.0285 -0.0399  a  A  -0.0334 -0.0380 -0.0487  PA  A 1 2 (error)  0.0000 0.0000 0.0090  0.0008 0.0004 0.0001  A  The results obtained during these measurements tell us that the current equipment set-up, instruments and experimental methods are applicable to get reasonable estimation o f y ci- The E M F H  measurement sounds so simple, but i n reality, it is not straightforward. It is very sensitive to any small change i n test conditions such as solution composition, temperature, and as well as the electrode condition. When temperature gets higher, one rarely obtains a stable reading using H 2  A g / A g C l couple with no junction. It is also expected that the same difficulty w i l l be encountered i n solutions with higher ionic strength. The interests o f hydrometallurgists are the higher temperatures and the upper limits o f the concentration. Through these E M F measurements variable combinations o f electrodes (pH probe, p H half cell-Calomel/Saturated K C 1 , H 2 - A g / A g C l , H2(ga )-Ag/AgCl/Saturated KC1) have been utilized i n S  order to choose the best combinations i n terms o f convenience i n use and accuracy o f the results. The H2(gas)-Ag/AgCl/Saturated K C 1 combination gives rather stable reading; however, sensitivity o f H  2  electrode disables the use o f these electrodes for the leach solutions. Therefore, regular p H  combination electrode is preferred for the purpose o f p H and redox potential measurement o f the leach solution.  65  Figure 4.1 Log y c i values: experimental, calculated b y the Harned equation vs. reference and the calculated values b y the Meissner method H  a) 2 5 ° C  b) 3 5 ° C  0.05  c) 4 5 ° C  0.05 Roy [43] Calc [Dixon] •Calc [Meisner] • 1=2 Experimental •1=2 Harned Eq.  0.03 0.01 -0.01 u a >g> -0.03 -0.05 -0.07 -0.09  -0.09 -0.11 0  0.5  1  0  0.5  -0.13 0  0.5  yMgcn-Ionic strength  yM ci2-Ionic strength  yM ci2-Ionic strength  fraction  fraction  fraction  g  g  1  4.1.2  Solubility of M g C h in water and H C l solutions  The next part o f the solution property measurement was the solubility measurement o f M g C l 2 salt i n acid solutions with varying concentrations. The solubility o f MgCl2 is determined as follows (Table 4.3 and Figure 4.2) as a function o f acid concentration and the temperature. Table 4. 3  Summary of M g C h solubility [g/1] in acid solutions HCl Molarity 6 3 1.5 0.75 0 (H 0) 2  22 242.8 371.3 423.7 455.8 485.6  Temperature, °C 50 75 333.2 428.4 428.4 485.6 471.3 499.9 523.7 504.6 523.7  82.75 452.2 499.9 537.9 557.0  A s acid concentration increases, the solubility o f M g C l decreases due to the limited availability o f 2  water molecules because o f hydration. Overall, solubility o f M g C ^ is determined to be within range of 243-557 g/1 over this specific acid concentration and temperature ranges.  Figure 4. 2  Solubility dependence of M g C b on acidity and the temperature  600  200 -I  1  1  1  0  25  50  75  1 100  Temperature, °C  67  4.1.3  Summary of the thermodynamic measurements  The E M F measurement o f the cell o f H C l - M g C l 2 - H 0 allowed determining the activity 2  coefficients o f H C l i n this mixture. Unfortunately, the activity coefficients o f the H C l are not sufficient to assign individual ion activities (e.g. H activity) since these require both acid and salt +  activities. Therefore, for high ionic strength solutions at high temperature, the individual ion activities can only be estimated based on the Meissner's method followed by the  approaches  described in Jansz (Note that extensive amount o f calculations were carried out i n the literature review including the mixtures used i n these experiments). The reference electrodes with no junction effect ( H 2 ( / A s - A g C l couple) were limited gas  especially i n concentrated solutions at higher temperatures due to unstable reading o f E M F . Although, the commercial electrodes (single and double junction electrodes whose compartments were filled concentrated K C 1 solution) provided a stable reading potential, the junction potential must be eliminated as accurately as possible. Nevertheless, the Henderson equation, which is applicable for calculating junction potential, is only valid up to an ionic strength o f six. Therefore, the Meissner's method followed by individual ion calculation best estimates the property o f strong solutions at higher temperatures. The solubility measurement o f MgCh  i n aqueous solutions o f hydrochloric acid provides  valuable data for the use o f mixture o f M g C k and H C l . A n increasing temperature results an increased solubility, whereas an increasing acid concentration results i n a decreased solubility o f MgCl2. The solubility limits o f M g C l  2  in water are determined to be 485.6 and 557 g/1 at 22 and  82.5°C, respectively. These limits decreased to 243 and 452 g/1 i n 6m acid solutions at 22 and 82.5°C, respectively. Exceeding these limits w i l l result i n "salting out" effects. Therefore, the M g C b concentration should be kept according to this range i n order to the get full effect o f the solution for the further leaching tests.  68  4.2  Individual mineral leaching The thermodynamic calculations i n section 2.2.6 predicted the dissolution behavior for the  selected sulfide minerals i n the mixture o f H C l and M g C ^ . To prove the consistency o f these predictions, a few o f the sulfide minerals were tested here.  4.2.1  Pyrite (P)  A high purity pyrite sample, which displays peaks for only pyrite on its X-ray patterns, was used i n this study. The chemical analysis o f the mineral sample showed an iron content o f 49.86 wt pet and a sulfur content o f 54.06 wt pet. Experiments were performed to study the influence o f the acid concentration, total chloride concentration, temperature and the leaching time on the dissolution o f iron from this mineral.  Figure 4. 3 Pyrite leaching: Effects of acid concentration, temperature and time  Figure 4. 4 Pyrite leaching: Effect of M g C h concentration at 60°C  a) Effect o f acid concentration: To determine the effect o f the acid concentration on the dissolution o f pyrite mineral, experiments were carried out with acid concentrations in the range 0 to 10m. The results are shown i n Figure 4.3, where we can observe that the acid concentration has no effect at 25°C (the lowest curve on this figure). This is what was predicted for pyrite in section 2.2.6 (Figure 2.14). O n the other hand, an increasing acid concentration has little promoting effect on iron dissolution i n the acid range 1 to 6m; thereafter iron dissolution declines i n the acid concentration range from 6 to 10m at  69  60°C (upper 3 curves on Figure 4.3) b) Effect o f total chloride concentration: To determine the effect o f total chloride on the dissolution o f pyrite, experiments were carried out in solutions with 3m H C l mixed with varying concentration o f M g C ^ in the range o f 0 to 2.75m. The results are shown i n Figure 4.4 from where we observe that the increasing total chloride has no effect on iron dissolution from pyrite. c)  Experiments were carried out at 25 and 60°C to determine the effect o f temperature on iron dissolution from pyrite. A t room temperature the pyrite mineral did not leach yielding less that one percent iron extraction, whilst at 60°C about 6% o f iron dissolved. Pyrite shows very refractory leaching behavior i n this mixture at all temperatures. This is consistent with the thermodynamic predictions i n section 2.2.6 for pyrite.  d) T o determine the effect o f leaching time, samples were taken at 4, 8 and 24-hour intervals. The results suggest that the longer retention time could result i n some small degree o f increased iron dissolution from pyrite mineral. e) Generally, the results o f pyrite dissolution are consistent with the thermodynamic calculations as predicted in section 2.2.6 (Figure 2.14). I.e. i n no case was there a sufficient proton activity to promote the significant break down o f pyrite.  4.2.2  Millerite (M)  Chemical assays and calculated mineral compositions o f the millerite sample used in this study are summarized i n Table 4.4. The mineral sample contains about 97% o f millerite and about 2 % o f pentlandite i n the form o f Ni4.5Fe4.5Sg. These two minerals were detected on X-ray diffraction patterns as shown i n section 4.4.2; however, a trace amount o f chalcopyrite was present based on elemental analysis. A n amount o f iron assay i n this sample belonged to the pentlandite and chalcopyrite. The trace element compositions were neither included i n this table nor used i n metal extraction calculations. Table 4. 4  Assays and mineralogical compositions of millerite sample  Elements Assay,% Minerals Assay, %  S(tot)  Ni  Cu  Fe  Ca  Co  Pb  Mg  32.00  59.29  0.52  13.78  0.09  0.24  0.13  0.03  M S (Millerite)  (NiFe) S  97.40  2.39  9  8  CuFeS  2  0.21  70  Throughout the experiments, the effects o f acid concentration, temperature and the leaching time were studied. Figures 4.5 and 4.6 show experimental results o f the millerite mineral dissolution in the mixture o f M g C ^ and H C l . Note that the metal extractions were calculated based on the solution sample analysis and the head grade o f the solid feed sample. Figure 4. 5 extraction  Millerite leaching: Ni  8=a 0 4-=°= 0  Figure 4. 6 extraction  ft^—-^—q  5 10 Acid Concentration, Molal  0  4hrat60C  -4hrat60C •24hrat 60C  —O—8hr at 60C  -6—24hr at 60C —o—24hr at 25C|  Table 4. 5 Acid cone, molal 1 3 6 10  Millerite leaching: Fe  5 10 Acid Concentration, Molal •8hr at 60C •24hrat 25C  Dissolution of metals from millerite leaching at 6 0 ° C N i extraction, % 4 4.55 3.66 3.82 6.02  8 6.70 5.28 5.46 6.84  Fe extraction, % Leaching time, hr 24 4 12.45 7.45 13.82 6.01 15.59 6.46 56.72 6.76  8 10.73 8.32 8.91 7.64  24 17.32 19.03 18.18 67.74  These results are summarized i n Table 4.5. The summary o f results is as follows: a) Effect o f temperature: Temperature has a promoting effect on millerite dissolution. There is no dissolution o f millerite at room temperature, whereas dissolution increases by 15-20 times at 60°C below 6m H C l i n mixture. A t 10m H C l i n mixture, this increase reached up to 60 times. These can be seen comparing the lowest curves on Figure 4.5 and 4.6 against upper curves. The effect o f temperature is consistent with the thermodynamic predictions in section 2.2.6 for millerite (Figure 2.14). b) Effect o f acid concentration: Hydrochloric acid concentration i n the range o f 1 to 6m does not have positive effect on increased dissolution. Thereafter, nickel dissolution  71  increases up to 40% i n the acid range o f 6 to 10m. Thermodynamically, it was predicted that millerite would dissolve at p H o f above zero as discussed i n section 2.2.6 (Figure 2.14). The leach solution o f 2m M g C l and 6m H C l creates pH~-2.0 at 60°C (Table 2.7) 2  according to the estimated p H values for mixtures. M a n y factors, such as kinetic factors, could cause the discrepancy between the prediction and experimental results, c) Effect o f leaching time: W e can observe that increased leaching time plays a major effect on millerite dissolution combined with increasing acid concentration. Sharp increase o f dissolution occurs just after 6m H C l i n mixture with 24 hours o f retention time. Further, the dissolution is expected to increase as acid increases. Hence, it is clear that the strong acid and longer leaching time are beneficial for millerite dissolution.  4.2.3  Violarite (V)  Chemical assays and the dominant mineral compositions o f the violarite sample used i n this study are summarized i n Table 4.6. The sample contained about 50% violarite and 2 3 % pyrite. The violarite weight percent was calculated based on the nickel assay. The remaining sulfur contributed to form pyrite mineral since the mineral supplier noted it as a possible association. Since all sulfur is used up for these two minerals, the remaining iron (17%) occurred probably not in the form o f sulfides. Note that 46% o f the total iron was associated in neither one o f the two main sulfide minerals.  Table 4. 6  Assays and mineralogical compositions of violarite sample Fe  Co  Cu  Mg  36.93  0.35  0.45  0.33  23.10 49.46 17.02 * remaining iron, not included in pyrite or in violarite  0.35  0.45  0.33  Elements assay, % . Mineral assay, %  S(tot)  Ni  33.39 FeS  19.26 FeNi S  2  2  4  *  Experiments were conducted to study the effects o f acid concentration, temperature and leach time on direct non-oxidative leaching o f the violarite sample. The results are graphically represented in Figures 4.7, 4.8 and 4.9 i n terms o f N i , C o and Fe dissolutions, respectively. Selected results are summarized i n Table 4.7.  72  Figure 4. 7 Violarite leaching: Ni extraction (2m MgCl )  Figure 4. 9 Violarite leaching: Fe extraction  Figure 4. 8 Violarite leaching: Co extraction  2  40 30 20 10 0  1  0  1  1  1  i  2 4 6 8 10 Acid Concentration, Molal  0  1  1  r  2 4 6 8 10 Acid Concentration, Molal  •4hrat 60C  •8hr at 60C  »4hrat 60C  •8hrat 60C  •24hrat 60C  •24hrat 25C  •24hr at 60C  •24hrat 25C  Table 4. 7  I  2  4  6  8  10  Acid Concentration, Molal •4hrat60C  —O—8hr at 60C  •24hr at 60C —o— 24hr at 25C  Ni & Fe extractions from violarite sample at 60 C Acid cone. molal 1 3 6 10  N i extraction, % 4 8.67 4.64 7.81 7.35  8 9.00 6.70 9.28 10.31  Fe extraction, % Leaching time, hr 24 4 16.00 37.24 19.61 37.36 18.76 36.48 32.30 34.36  8 39.05 37.68 38.68 35.83  24 50.05 53.38 53.26 58.27  Based on these results, the following effects are observed: a) Effect o f acid concentration: Below 6m H C l i n the mixture, violarite dissolution is unaffected by acid concentration at both 25 and 60°C. A n increase o f acid concentration up to 10m results i n a 22% increase o f N i extraction from violarite. The same results were found for C o . O n the other hand, Fe shows a different behavior. It is clear that this mineral sample contained acid soluble iron that dissolved rapidly i n a very low acid concentration (Figure 4.9). Thereafter, Fe dissolution slightly increases as violarite dissolves as shown by the upper curve on Figure 4.9. A s mentioned before, 46% o f the total iron is associated i n neither one o f two main sulfide minerals; b) Effect o f temperature: A s always, an increasing temperature promotes violarite leaching. It is expected that even higher temperatures (up to 100°C or just below the boiling point o f a leach solution) could result i n higher metal extractions; c) Effect o f leaching time: Prolonged leaching time seems to promote mineral dissolution.  73  However, an increased temperature and a strong acid solution could result in high dissolution within a short leaching period.  The violarite feed contained about 17% o f iron that was associated neither i n violarite nor i n pyrite. The extra iron in this sample could be i n the form o f Fe20"3 or FeO(OH). If it were hematite, the following reaction would take a place. F e 0 + 6HC1 = 2 F e C l + 3 H 0 2  3  3  ( R X N 4.1)  2  It could cause FeNi S4 leaching by:  .  2  F e N i S + 6 F e C l = 2 N i C l + 7 F e C l +4S 4  3  2  ( R X N 4.2)  2  In this case, violarite is leached by the effect o f a ferric ion not by the effect o f higher acid concentration. Therefore, feed and solid residue were subjected to X R D i n section 4.4 to clarify the leaching chemistry o f violarite.  4.2.4  Troilite (T)  Chemical and mineral assays o f troilite sample are summarized in Table 4.8. Based on the iron content, 90% o f the total sample represented troilite mineral. Remaining sulfur (-0.018wt%) was associated with other base metals i n this sample. Table 4. 8  Assays and mineralogical compositions of troilite sample Elements assay, % Minerals assay, %  The effects  S(tot) Fe 34.59 57.23 FeS (Troilite) 90.09  Co 0.05  Cu 8.68  Mg 0.41  Ni 027  0.05  8.68  0.41  0.27  o f the acid concentration, temperature and the leaching time on troilite  dissolution were investigated and the results are presented i n Figures 4.10-4.12. Based on leaching kinetic curves o f troilite leaching, the following kinetic evidence can be drawn: a) Effect o f acid concentration: A t room temperature, iron dissolution o f troilite steadily increases as acid concentration increases from 0 to 5m. Thereafter, dissolution o f iron almost doubled i n the range o f 5 to 6m as seen i n Figure 4.10. A steady increase o f C u extraction is observed as shown in Figure 4.11. O n the other hand, 95% o f iron dissolved within the acid range o f 1 to 3m (Figure 4.12) at 60°C. The solutions in this case w i l l have pH—1 as it was predicted i n section 2.2.5.2 (Table 2.7). The thermodynamic calculation i n section 2.2.6 (Figure 2.14) predicted that the troilite leaches in the p H range o f -1.0 to -0.5 at these temperatures. Therefore, the experimental results are  74  consistent with both thermodynamic predictions. b) Effect o f temperature: A n increasing temperature results in a much higher dissolution o f troilite even at lower acid concentration. c) Effect o f leaching time. Dissolution percent increases with longer retention time but leaching time has a lesser effect than the acid concentration and the temperature. A low acid concentration at a higher temperature w i l l result i n near complete dissolution o f troilite mineral. Figure 4. 10 Troilite leaching: Fe extraction at 25°C (2m MgCI )  Figure 4.11 Troilite leaching: C u extraction at 25°C  2  4.2.5  Figure 4.12 Troilite leaching: Fe extraction at 25 & 60°C  Heazelwoodite (H) Dominant elemental assays  i n the heazelwoodite sample are  shown in Table 4.9.  Heazelwoodite (NisS ) mineral composition i n this sample is calculated based on N i assay o f this 2  sample. Assuming all nickel assay forms heazelwoodite minerals, about 13.5 percent o f total weight accounts for this mineral. Table 4.9 S(tot) 4.51  Assay of heazelwoodite sample, % Si0  2  23.78  MgO 0.00  Al 1.63  Ca 1.29  Co 0.31  Cu 0.13  Fe 14.58  Mg 15.83  Ni 9.92  The effects o f the acid concentration, temperature and the leaching time were investigated,  75  and only dissolution results o f N i from this sample are presented here. Some o f selected results o f heazelwoodite leaching are summarized i n Table 4.10. More studies w i l l be covered i n matte leaching which is an excellent representative o f the heazelwoodite mineral. Figure 4.13  Heazelwoodite leaching: Ni extraction (2m MgCh) 80  X  40  Nic  a © 60  20  W "3  0 0  2 4 6 8 10 Acid Concentration, Molal •4hrat 60C •24hrat 60C  •8hrat 60C •24hrat 25C  a) Effect o f acid concentration: Heazelwoodite started to dissolve at the beginning stage o f acid addition as low as l m . Thereafter, there is no significant effect o f acid addition on N i extraction; b) Effect o f temperature:  Although, heazelwoodite leaches at room temperature,  the  temperature increase from 25 to 60°C resulted i n 6 times faster leaching kinetics (two overlapped lower curves). c) It seems that the retention time did not play as significant a role as the temperature on the heazelwoodite dissolution and kinetics. d) The heazelwoodite dissolution was predicted in section 2.2.6. According to Figure 2.14, a significant amount o f heazelwoodite ( a [ N i ] = l ) dissolves at p H o f about 2.0. Table 2.7 2+  (section 2.2.5.2) estimates the p H o f this solution (2m M g C l 2 - 2 m H C l ) is about -0.7 at 60°C. The discrepancy between the prediction and the experimental results may be resulted by kinetic factors and the composition o f this sample. Table 4.10 Acid cone. molal 1 3 6 10  Summary of heazelwoodite leaching at 60°C N i extraction, % 4 29.80 26.95 27.70 25.21  8 34.94 31.73 32.93 31.41  Fe extraction, % Leaching time, hr 24 4 55.06 55.73 53.22 72.12 60.35 66.02 64.76 60.76  8 70.03 72.57 66.15 62.42  24 79.07 82.65 79.85 74.56  76  4.2.6  Chalcopyrite (C)  Based on the element assays, possible mineralogical compositions o f this sample were calculated as shown i n the next table along with assays o f the predominant elements. O n the X-ray diffraction analysis, peaks were only detected for chalcopyrite. Table 4.11  Assays and mineralogical compositions of chalcopyrite sample Element assay, % Mineral assay, %  S(tot) • Cu 33.29 35.30 CuFeS (Chalcopyrite)  Fe Ni33.75 0.28 Ni4.5Fe4.5Sg (Pentlandite)  99.5  0.5  2  The mineral was subjected to leaching i n the mixture o f strong acid and magnesium chloride solutions to determine the effect o f acid concentration, and the leach temperature. A l l tests were run with four hours o f retention time. The leaching results are presented i n Figure 4.14 and summarized in Table 4.12. Figure 4.14  Chalcopyrite leaching: Metal extractions 25 20 15 10 5 0 0  2 4 6 Acid concentration, m  8!  * - C u @60C, Cl-total =284g/l -o— Fe @ 60C, Cl-total = 284g/l • Cu @ 100C, Cl-total=390g/l • Fe @ 100C, Cl-total = 390g/l  Table 4.12  Summary results of chalcopyrite dissolution Acid cone. molal 1 3 5 7  Cu extraction, %  Fe extraction, %  60°C 0.7 1.44 1.51 1.51  60°C 1.65 3.27 3.57 4.02  100°C  22.18  100°C  22.71  Dissolution characteristics o f the most abundant copper mineral are as follows: a) Effect o f acid concentration: A t low temperature (60°C), an increasing acid concentration has a weak effect on metal dissolution. It is observed that the iron extraction is higher than copper extraction. This evidence suggested a selective leaching o f iron over copper,  77  leaving copper enriched solid residue as expected, thermodynamically (Table 2.11 reaction for chalcopyrite). To study further, a single test was carried out i n mixtures with 7m H C l and 2m M g C l at 100°C. 2  b) Effect o f temperature.  A t a higher temperature,  both temperature and the  acid  concentration resulted i n increased metal dissolutions. The results at 100°C clearly indicate that the same amount o f copper and iron dissolved meaning that there was no phase transformation from chalcopyrite to its copper enriched phases Cu2- S. The solid x  residue was then subjected to X R D to address i f there was any phase transformation. In contrast to the prediction in section 2.2.6, chalcopyrite could be directly attacked by high acid at high temperature forming cupric and ferric chlorides. This needs more study and investigation.  4.2.7  Summary of individual mineral leaching  A few o f the sulfide minerals were tested here in mixtures o f H C l and MgCl2. Each mineral showed a unique dissolution behavior i n this mixture depending on acid concentration and the temperature. Pyrite is not leachable i n this mixture. Increases o f H C l concentration, up to 10m, and the temperature increase from 25 to 60°C, have resulted i n only 6% iron dissolution from pyrite. In contrast, troilite - another iron mineral leached reasonably well yielding 90% iron extraction at 60°C in mixtures with 3m H C l . The chalcopyrite showed a refractory behavior at 60°C in solutions with varying H C l concentrations. However, 22% o f both copper and iron were extracted at 100°C in mixtures with 7m H C l . A m o n g the nickel sulfides, heazelwoodite showed a highly favorable dissolution behavior i n mixtures with H C l concentrations as low as l m within a short leaching period. Millerite dissolution depends on acid concentration, above 6m o f acid, 60% o f nickel leached into solution at 60°C. The behavior o f violarite depends on acid level; however, only 30% o f nickel transferred into solution i n mixtures with 6m o f acid at 60°C. A n increasing temperature plays a significant role on increased dissolution, e.g. 15-20 times increase in case o f millerite. Overall, both temperature and the acid concentration have significant effects on metal extraction and kinetics for the selected sulfide minerals. Most o f the leaching results o f individual minerals were consistent with those predicted thermodynamically (in sections 2.2.5-2.2.8) i n terms of acid concentration and temperature.  78  4.3  Commercial concentrates and matte leaching The leaching results o f individual minerals suggest possibilities and conditions o f processing  commercial sulfide concentrates i n this mixture. The objectives o f these leaching experiments were to achieve high metal extractions, to investigate leach parameters such as leach time, temperature, acid concentration and the addition o f CuCl2 or FeCL, to the leach system. Equipment set-up for this commercial sample leaching was the same as for the individual minerals. The only differences were solid/liquid ratio and the temperature. S / L ratio o f 25g/500ml was maintained for these tests. A l l tests were run at 100°C except initial tests for a low M g O concentrate.  4.3.1  Low M g O concentrate One o f two identical concentrate samples with low M g O content was tested. Several key  results are outlined below. Note that all test conditions are i n the absence o f oxygen. a) Effect o f leach time and the temperature: Initial leaching tests (at 60°C) were carried out in solutions with 10m H C l mixed with 2m M g C L . to get an idea o f retention time. The results show high metal recoveries can be achieved within 4 hours leaching time (Figure 4.15). The present goal is also to achieve high recoveries i n solutions with lower acid concentration. Therefore, subsequent test were carried out with a retention time o f 4 hours and an increasing temperature up to 100°C. b) Effect o f acid concentration: In order to determine the effect o f acid concentration on dissolution, tests were performed in the mixtures o f H C l - M g C l 2 with acid concentrations of 2, 6 and 8m. Results show that metal dissolutions are strongly acid dependent yielding around 75% extractions o f N i , C u and Fe and about 52% extraction for C o at 6m H C l i n mixture with a retention time o f 4 hours. The results at 8m H C l i n mixture were obtained with a retention time o f 2 hours (The points at 8m H C l on Figure 4.16). N i , Fe extractions reached up to 95%, and C o extractions increased up to 75% (Figure 4.16). c) Effect o f C u C ^ : To determine the effect o f C u C l addition, the concentrate sample was 2  leached in mixtures o f 6m H C l - 2 m M g C L . at 100°C with a retention time o f 4 hours. 0.5m C u C b was added into solution. This addition resulted i n a decrease o f extraction for both N i and Fe o f 10%, an 18% decrease for C o , and a 22% increase for C u compared to metal extractions with no copper addition (Figure 4.17). Thus, addition o f CuCL. has a negative effect on increased dissolution o f N i and C o . There are two possible reasons for  79  these low metal extractions. The C u Ni  2 +  ion tends to get complexed with chloride ions than  ion (Table 2.12). Therefore, cupric ion i n solution w i l l have more affinity to  precipitate nickel chlorides as discussed i n section 2.2.7 (as illustrated by the example i n section 2.2.7, R X N 2.7). The second possible reason is explained by strong tendencies o f reduction by H2S gas as discussed i n section 2.2.6b ( R X N 2.2). The higher C u  Cu  concentration favors this reduction. Therefore, there was no beneficial effect o f the C u  2 +  ion on metal extraction; instead, the reduced copper (or copper sulfide may have formed) covered the mineral surface. d) Effect o f F e C b : The leach conditions for these tests were the same as before, instead o f adding CuCl2, 0.5m FeCLj was added into leach solution. Addition o f F e C b resulted i n a 31, 33 and 40% decrease o f Co, N i and C u extractions, respectively. The addition o f this salt did not promote extractions (Figure 4.18). The reason is explained by the same phenomena as before. Even F e  3 +  has more tendencies to form chloro-complexes, which  may precipitate (or decreasing extraction) other metal cations such as N i , C o 2 +  C u . In addition, as discussed in section 2.2.6b, the F e 2 +  3 +  2 +  and  has a strong tendency to be  reduced by H2S gas ( R X N 2.3) forming elemental sulfur. Elemental sulfur may form a passive layer on the particle surface preventing further reaction. e) Figure 4.19 shows the dissolution o f magnesium from this concentrate.  63% o f  magnesium was dissolved with no addition o f cupric and ferric chlorides. The addition o f 0.5m o f either salts resulted i n about 96% magnesium extraction from this concentrate.  Figure 4.15 Low M g O concentrate: Effect of leach time (10m HCl-2m M g C l at 60°C) 2  Figure 4.16 Effect of acid concentration (2m MgCI , t=2 & 4 hr at 100°C) 2  80  Figure 4.17 Effect of C u C l addition (6m H C l , t=4 hr at 100°C)  2  Figure 4.18 Effect of F e C l addition (6m H C l , t=4 hr at 100°C)  3  Figure 4.19 The dissolution of magnesium (6m H C l , t=4 hr at 100°C)  0.0  0.1  0.2  0.3  0.4  0.5|  Added salt concentration, m  Generally, high metal extractions from low M g O concentrate can be obtained i n mixtures with higher than 8m acid concentrations with a retention time o f 2 hours at 100°C. The strong oxidants such as cupric and ferric chlorides do not promote metal extractions i n this specific test condition  (oxygen has been  excluded). The decreased  metal extractions were caused  by  complexation and solubility behaviors o f metals that present i n solution. A l s o , interaction o f dissolution product gases such as H S and H with the metal cations in solution has a deleterious 2  2  effect on metal extractions as explained above.  4.3.2  High M g O concentrate  One o f two identical concentrate samples with high M g O content was tested. The effects o f leach time, acid concentration and the addition o f strong oxidants were studied and the following results were obtained. a) Effect o f leach time and temperature: The results o f individual minerals and previous concentrate sample have suggested a leach temperature o f 100°C for the subsequent tests for high metal recoveries. So, all tests on this sample were run at this temperature. To determine the effect o f leach time, the concentrate sample was leached i n the mixture o f 6m H C l - 2 m M g C l . Unlike low M g O concentrate, the high M g O concentrate yielded 2  high metal extractions within retention time o f one hour (Figure 4.20). Subsequent tests were carried out with a retention time o f one hour.  81  Figure 4. 20 High M g O concentrate: Effect of leaching time (6m H C l - 2m M g C l at 100°C) 2  Figure 4. 22 Effect of C u C l addition (6m H C l 2m M g C l , t=lhr at 100°C) 2  2  Figure 4. 21 Effect of acid concentration (2m MgCI , t=lhr at 100°C) 2  Figure 4. 23 Effect of FeCI addition (6m H C l - 2m M g C l , t=lhr at 100°C) 3  2  Figure 4. 24 Dissolution of magnesium (6m H C l - 2m M g C l , t=lhr at 100°C) 2  100  100  0.00  0.25  0.50[  CuCh concentration, m  0.0  0.1  0.2  0.3  0.4  0.5|  Added salt concentration, m  b) Effect o f acid concentration: The mixture with 2m H C l i n mixture has resulted poor metal extractions. In contrast, 95% o f N i , 9 1 % o f Fe, 76% o f C o and 19% o f C u extractions were obtained from leaching i n mixtures with 6m acid concentrations (Figure 4.21). c)  Effect o f C u C l  2  addition: To determine  the effect  of CuCl  addition on metal  2  dissolutions, tests were performed i n mixtures o f 6m H C l - 2 m M g C l with the addition o f 2  82  0.05, 0.2 and 0.5m o f C u C l . The addition o f a small amount o f C u C l 2  2  (0.05m) has  resulted i n the decrease o f metal extractions o f 66.5, 90, 46 and 72% for C o , C u , Fe and N i , respectively. Thereafter, addition o f 0.2 and 0.5m o f C u C l  2  has resulted i n the  increase o f metal extractions; however, the metal extractions were lower than the extractions obtained with no addition o f C u C l (Figure 4.22). One possible reason for this 2  low extraction may be explained by the discussion i n section 2.2.6b. The C u  2 +  ion is  more favorable to be precipitated by H S gas, which is the product o f nickel sulfide 2  dissolution by the direct attack o f acid ( R X N 2.2). Hence, the reduced product o f copper prevents further dissolution o f minerals. d) Effect o f F e C b : To determine the effect o f FeCl3 on metal dissolutions, the sample was leached i n the mixture o f 6m H C l - 2 m M g C l with the addition o f 0.2 and 0.5m o f F e C ^ . 2  A s F e C b increases, extractions o f N i , C o and C u were decreasing. The addition o f 0.5m FeCi3 has resulted in the decrease o f metal extractions o f 60-64% for N i , C o and C u , and the increase o f 8% for iron extraction (Figure 4.23).  The reason for low metal  extractions with the addition o f ferric ion can be explained as follows: the ferric reacts with H S gas as i n R X N 2.3 (section 2.2.6b); as determined before, FeS is easily leached 2  in strong acid solution; and the elemental sulfur covers mineral surface causing decreased mineral dissolution. e) Figure 4.24 shows the dissolution o f magnesium from this concentrate. About 83% o f magnesium was dissolved with no addition o f cupric and ferric chlorides. The addition o f 0.5m o f either salts resulted in about 96% magnesium extraction from this concentrate.  Generally, the high M g O concentrate is leachable i n mixtures with 6m acid concentrations with a retention time o f one hour at temperatures o f 100°C at ambient pressure. The high M g (the most problematic substance during P A L ) was dissolved with a significant extent (83%). In a process flowsheet this magnesium could later be recovered as described by pyrohydrolysis process. The addition o f C u C l  2  decreased N i , C o and Fe extractions. Similarly, addition o f FeCh  promoted Fe extraction and depressed N i , C o , C u extractions from this concentrate sample (Figure 4.22). The reasons o f lower metal extractions with the addition o f ferric and cupric chlorides were explained by the same phenomena described in the previous section.  83  4.3.3  Nickel matte  One o f four identical matte samples supplied by B H P Billiton was studied here. The effects o f temperature, acid concentration and the leaching times were investigated. a) Effect o f temperature: Temperature has a significant effect on increased extraction and faster kinetics. Temperature increase from 60 to 100°C has resulted i n the following: •  This accelerated the dissolution kinetics o f nickel by almost four times. The same extractions were obtained in 8 and 2 hours o f the leaching period at 60 and 100°C, respectively (Upper curve on Figure 4.25 against upper curve on Figure 4.29).  •  Faster kinetics and even higher cobalt extractions were observed due to the temperature increase (compare upper curve on Figure 4.26 against second curve from the top on Figure 4.29). Similar phenomena were observed for iron extraction from this matte sample.  •  Copper extraction from this sample increased by 9% i n a four times shorter leaching period as a result o f temperature increase from 60 to 100°C. 83% C u extraction at 60°C i n 8 hours vs. 92% i n 2 hours at 100°C (Figure 4.27 against lower curve on Figure 4.29).  b) Effect o f acid concentration: Most o f the metals except copper dissolved to a significant extent in solutions with acid concentrations as low as 3m (Compare Figures 4.25-4.28). In contrast, copper i n this matte sample started to dissolve in solutions with 6m H C l in the mixture. This suggested leaching matte samples at 100°C i n solutions with 6m o f acid in order to get higher metal extractions (including copper). The low copper extraction is explained by the following phenomena. A s discussed in section 2.2.6a, heazelwoodite dissolution i n strong acid produces both H S and H gases (Table 2.11). Both gases are 2  2  strong reducing agents. A m o n g metal cations i n solution ( N i , C o , C u ) , cupric ion 2 +  2 +  2+  has a strong tendency to be reduced by any one o f these gases ( R X N 2.2 and R X N 2.4 i n section 2.26b). This reduction results i n a lower copper extraction. c) Effect o f leaching time: Tests at 60°C showed that leach time increase resulted i n higher metal extractions (Figure 4.25 - Figure 4.28). O n the other hand, there was almost no effect o f leaching time increase from 2 to 4h at 100°C. Most o f the valuable metals o f this matte sample were easily extracted at 100°C in solutions with 6m H C l within one hour.  84  Figure 4. 25 Matte leaching: Ni extraction at 60°C (2m MgCl ) 2  Figure 4. 26 Matte leaching: Co extraction at 6 0 ° C (2m MgCl ) 2  Figure 4. 28 Matte leaching: Fe extraction at 60°C (2m MgCl ) 2  Figure 4. 27 Matte leaching: C u extraction at 6 0 ° C (2m MgCl ) 2  Figure 4. 29 Matte leaching: Metal extractions at 100°C (2m MgCl ) 2  „100  a .2 95 w OS  S W 0 2 4 6 8 10 Acid Concentration, Molal •2hr at 60C •8hr at 60C  •4hr at 60C  90  3  80 85 1 2 -Ni -Cu  Test cond: 6m HC12mMgC12, 100C,  3  4  Leach Time, hr -a—Co —o—Fe  Overall, nickel matte can be easily processed i n the mixture o f H C l and M g C l just below the 2  boiling point o f the solution (~100°C). A t this temperature, complete dissolution o f nickel matte is expected within one hour o f leaching i n solutions with 6m o f hydrochloric acid. 6m o f acid is required i n order to achieve higher copper extraction.  85  Metal extractions from matte sample at 60°C  Metal extractions, % Co  Cu  Fe  Ni  Leach time, hr  Leach time, hr  Leach time, hr  Leach time, hr  lal  id traion,  Table 4.13  O C o < on 1 o  2  1 3 6 10  37.18 58.92 70.32 64.57  Table 4.14  4  8  2  4  8  48.44 63.66 0.50 0.75 0.59 70.69 78.49 1.82 3.78 5.63 71.23 80.04 8.79 38.97 83.43 63.82 78.44 41.99 46.48 91.09  2  4  52.23 63.22 70.97 64.28  8  63.87 8038 71.12 79.72 70.69 81.75 63.48 80.44  2  4  30.91 59.65 73.47 66.82  41.90 73.19 75.36 66.05  Metal extractions from matte sample at 100°C L.time, hr 2.00 4.00  Co 97.41 97.31  Cu 91.83 90.20  Fe 96.46 96.79  Ni 99.92 100.00  8 64.16 94.57 94.36 96.05  4.4  X R D , S E M - E D X analyses  The leaching results described i n the previous sections give rise to a number o f questions. A m o n g them are how individual minerals and the commercial samples were dissolved in this mixture. To address these issues, X R D and S E M - E D X analyses were performed on the selected solid samples before and after leaching.  4.4.1  Pyrite and leach residue  Figure 4.30 displays X-ray patterns o f pyrite and its leach residue. Both patterns show exact peaks for natural pyrite. Figure 4. 30  X-ray patterns of pyrite and pyrite leach residue (10m HCl-2m M g C l at 60°C) 2  inoline < | v | ? [ B [ B | l T g SCAN:40.0;80.0/0.05/1.5(sec)Xu(40kV.20inftM[ma>i)°3676.01/24/0607:02p  <40.0Q-80.0Q> P PDF P CPS P 21(0) 10.0  j ] Sj  u  Overlaid patterns  1  \, It BBnBDBBBBBIIIBB Jj|042-1340> Pyrite-FeS2  I i  2  ~  >-. Q_  a.  ~ ^  1  T|-M*l»H*irTiiRFll »  Residue  ><  CL  Pyrite • FeS2  £  J  J  40  .-2  >s  60  CL  « >>  £ >>  Feed  J Jl Jl  Q-  •  <D  CL 70  >>  a.  80  Thermodynamically, the following reaction is predicted for the direct dissolution o f pyrite: FeS + 2 H C l 2  ( g )  = FeCl  2 ( a q )  + S° + H S 2  ( g )  ( R X N 4.3)  Since the leach residue did not show any peaks corresponding to elemental sulfur, a S E M E D X was performed to investigate the composition o f the leach residue.  87  The following image was obtained from the S E M - E D X analysis o f the pyrite leach residue. The image contains mostly pyrite (Spot2) and sulfur covered pyrite particles (Spotl), based on the S E M - E D X analysis. Figure 4.31  S E M picture of pyrite leach residue (10m HCl-2m M g C l at 60°C)  Table 4.15  Composition of pyrite leach residue (10m HCI-2m MgCI at 60°C)  2  2  wt % as wt % as  Overall Fe S 0.495 0.505 Fe FeS  Fe 0.497 Fe  S 0.503 FeS  Fe 0.455 FeS  S 0.545 S  0.055  0.060  0.940  0.977  0.023  2  0.945  Area 1  Spot 1  2  2  Spot Fe 0.491 Fe 0.048  2 S 0.509 FeS 0.952 2  Spot Fe 0.505 Fe 0.075  3 S 0.495 FeS 0.925 2  Table 4.15 summarizes the composition o f the spots identified on Figure 4.31. Since only about 6% o f pyrite was leached, the reaction product (elemental sulfur) cannot be identified on the X R D patterns. This explains why Figure 4.30 displays the peaks only for pyrite. Hence, the qualitative values obtained by S E M - E D X were used to calculate the weight fractions o f pyrite and elemental sulfur as shown in Table 4.15. In most cases, the product is iron enriched, except for S p o t l . Spotl consists o f about 98% pyrite and 2 % elemental sulfur. Therefore, pyrite dissolution can be concluded as follows, based on the leaching, X R D and S E M - E D X results: •  Pyrite is the refractory mineral i n this mixture; yielded only about 6% iron extraction for 24 hours o f leaching time in a mixture o f 10m H C l and 2m M g C l ; 2  88  •  Elemental sulfur seems to be the dissolution product as expected ( R X N 4.3); however, this trace amount o f elemental sulfur was hardly detected on the X R D ;  •  About 5% o f iron enrichment occurred on several areas (mostly black covered particles on Figure 4.31) o f the leach residue.  4.4.2  Millerite and leach residue  Figure 4.32 displays X-ray patterns o f the millerite sample and the leach residue. A s reported before, this sample contains over 9 5 % millerite and about 3% pentlandite. Both minerals were detected on the X-ray patterns o f the feed. The patterns o f the leach residue contained exactly the same peaks o f millerite and pentlandite as before leaching. N o peaks disappeared and no new peaks appeared as a result o f leaching; however dissolution was only partual. Therefore, millerite, as predicted thermodynamically dissolved, as shown below.  NiS + 2 H C l  Figure 4. 32  ( g )  - NiCl (a + H S( 2  q)  2  g)  AG° = -15.76 kcal/mol  ( R X N 4.4)  X-ray patterns of millerite and its leach residue (10m HCl-2m M g C l at 60°C) 2  89  4.4.3  Violarite and leach residue  In section 4.2.3, a question was posed regarding whether the violarite mineral was leached by the effect o f the ferric ion or by the effect o f a strong acid. To answer this question, X R D patterns o f the feed and the solid residue are compared below. The peaks on the X R D pattern o f the feed (Figure 4.33) were identified as violarite and pyrite. These are consistent with those found in section 4.2.3. The extra iron in the feed was identified as siderite (FeCO^), in addition to a trace amount o f hydromolysite (FeCl3*6H20). N o peaks for hematite were found, meaning that the violarite was leached by the effect o f increased acid concentration. Figure 4.34 shows compared peaks o f violarite feed and the leach residue. A s a result o f the 30% N i and about 60% Fe extraction, the peaks for violarite and pyrite remained. This is consistent with the fact that pyrite is refractory as described before. Some peaks, belonging to siderite, disappeared resulting in about 60% iron extraction. This proves that the violarite was leached by the direct attack o f the strong acid in the mixture.  Figure 4. 33  X R D patterns for violarite mineral sample Sr^:«.0/120.nrt.05/1.5(stcLQ44<^  P O F T CPS T~ 2«0)|o.O  * sj  Counts  X III  ±1  ||fe  ~K\ii.M.  ill  it  il  VMt-FMX*  |i|s|c|n|*|h|ti|ii|*Miii|x|hir-M|»|>l*l  Siderite • FeC03 Hydromo^sile • FeC]3!6H20  | D ? c 0) c  H P>\  ]  s  •  : |  1 2  i ^ HF 5  \ ill )  *  v  i § IP J  7  i i l l  1  ^ f  1  *  1  m 0  90  Figure 4. 34  4.4.4  Compared X R D patterns for violarite and leach residue  Chalcopyrite and leach residue X R D patterns o f chalcopyrite and its leach residue both show peaks for chalcopyrite (Figure  4.35). A s reported before, about 22% o f this mineral was dissolved at 100°C. According to the nonoxidative dissolution o f chalcopyrite, the leaching product is supposed to contain some covelliteCuS (or copper enriched products-Cu2. S o f CuFeS2), as predicted thermodynamically. x  CuFeS + 2 H C l 2  ( g )  = CuS + F e C l + H S 2  2  A G = -3.8 kcal/mol 0  ( g )  ( R X N 4.5)  Since X R D o f the leach residue did not show any peaks corresponding to CuS, and displays peaks for only chalcopyrite after 22% o f dissolution, the probable dissolution o f chalcopyrite is expected as follows: CuFeS + 4 H C l 2  ( g )  = CuCl (a ) + FeCl aq) + 2H S( ) 2  q  2(  2  g  AG°=47kJ/mol at 100°C  ( R X N 4.6)  However, Gibbs' free energy o f this reaction is positive, the leach solution and the X-ray patterns o f leach residue suggested that the dissolution o f chalcopyrite follows this reaction [ R X N 4.6].  91  Figure 4. 35 100°C)  X-ray patterns of chalcopyrite and its leach residue (7m HCl-2m M g C l at 2  92  4.4.5  Low M g O concentrate and its leach residue  The detailed mineral assays o f the low M g O concentrate were kindly supplied by B H P Billiton (Table 4.16). X-ray patterns o f the concentrate sample were consistent with the B H P Billiton's mineral assays (Figure 4.36). Note that the Ni-sulfide was identified as pentlandite and the sample contained a substantial amount o f pyrrhotite. Table 4.16  Detailed mineral assay of low M g O concentrate (supplied from B H P Billiton) Ni-sulphide Ni-arsenide Pyrite Pyrrhotite Chalcopyrite Tochilinite Magnetite Serpentine Talc Magnesite Dolomite Mg-silicate Hydr-carb Felsic Total  Figure 4. 36  32.58% 0.03% 11.81% 29.38% 0.55% 3.00% 2.72% 5.51% 9.93% 0.36% 0.84% 2.48% 0.13% 0.68% 99.98%  X-ray patterns of low M g O concentrate P«illatti»e-|F«.Ni|933 PyrrtioSte W Fel.jiS Tafc2M-Ms33i*010i0H|2 PytSe • FeS2  Feed  Overlapped patterns o f the low M g O concentrate before and after leaching shows diminished peaks for residue (Figure 4.37). X-ray patterns o f the solid residue, where the highest metal recoveries were obtained, shows peaks for talc, pyrite and quartz (Figure 4.38). The pentlandite and  93  pyrrhotite peaks disappeared. This confirms that pyrrhotite and pentlandite are soluble in this mixture. Figure 4. 37 MgCl )  Overlapped X - r a y patterns of low M g O concentrate and its residue (8m HCl-2m  2  irolme < | : | •> 1 B | B| I H  lu  SCAN 40 0/100.0/0.05/1.5(sec], Cu(40kV.20n-A). I[m«>0-1198. 02/03/06 02:20p  r  p p F r " C P S r~ 2fl(o) joo  Overlaid patterns  |1B5-8.2-2.raw] 185-8.2-2 • Gartold  i|T|-M-kl»IH«l*hlHlxlH^[jia;]KiiM^Mk«,ff.  'HQ  Residue  Feed  - i — i — i — i — + -  Figure 4. 38  X-ray pattern of low M g O concentrate residue (8m HCl-2m M g C l at 100°C) 2  1«1 ' 1: I I " I 111 042-1340> Pyrite • FeS2 Millerite - NiS Pyrite - FeS2 Quartz - Si02 Talc-2M -Mg3Si4O10(DH)2  94  Based on the element assays determined by the S E M - E D X , the major mineral assays were calculated (Table 4.17) for the selected spots on the S E M image (Figure 4.39). The calculated mineral assays were consistent with those on the X-ray patterns (Figure 4.38). The dark and light dark spots on the S E M image had no distinction in terms o f elements and minerals. This means that it is unlikely that a product layer formed on the surface o f particles. Therefore, the low M g O concentrate leached in strong acid solutions leaving a solid residue o f pyrite, talc and quartz.  Figure 4. 3 9  S E M image of low M g O concentrate leach residue (8m HCl-2m M g C l at 100°C)  Table 4.17  Contents of low M g O concentrate residue (8m HCl-2m MgCl )  2  2  1B5-8.2-2  wt. fraction of elements based on S E M - E D X  ID on SEM Image  s  Si  O  Fe  Ni  Mg  Na  wt. fraction of elements and calculated minerals Sum  S  SiO,  O  FeS  Ni  Mg Si O (OH)  0.017  0.240  0.078  0.299  0.042  0.318  0.994  0.011  0.266  0.070  0.277  0.032  0.338  0.995  Spot 1  0.177 0.183 0.392 0.139 0.042 0.062 0.002 0.996 0.159 0.199 0.410 0.129 0.032 0.065 0.005 1.000 0.162 0.200 0.410 0.130 0.033 0.063 0.003 1.000  0.013  0.277  0.278  Spot 2  0.033  0.166 0.192 0.400 0.137 0.033 0.064 0.009 1.000  0.252  0.293  0.033  0.328 0.332  0.997  0.009  0.068 0.072  Overall Area 1  2  3  4  10  2  Sum  0.991  Addition o f 0.5m C u C h into leach solutions o f 6m H C l and 2 m M g C h did not improve metal extractions (Figure 4.17). However, peaks for pentlandite disappeared as a result o f 60% N i and 66% Fe dissolution. Peaks for pyrite and talc appear on the X-ray patterns o f the leach residue. N e w peaks for quartz also appear because o f leaching (Figure 4.40). To address the lower metal  95  dissolutions, leach residue was subjected to S E M - E X D . S E M image displays particles covered with flaky type dark layer (Figure 4.41). The calculated mineral assays based on the S E M - E D X are consistent with the peaks appear on the X-ray patterns. In addition, a significant amount o f copper assay was detected. The darker area (e.g. Area 4 in Figure 4.41) contains more copper as seen on the last row o f a summary table (Table 4.18). Therefore, an excess amount o f copper in the leach solution formed an insoluble layer (probably combined with leaching products) on the surface o f particles, and retarded the dissolution o f the minerals further. The S E M - E D X results confirm the reasons for low metal extractions as explained in section 4.2.1. This was actually predicted in section 2.2.6b ( R X N 2.2). Addition o f FeCi3 showed similar retarding effects on the dissolution. This is most likely due to formation o f a sulfur-enriched surface layer that may be expected to retard non-oxidative leaching.  Figure 4. 40 X-ray pattern of low M g O concentrate and its leach residue (6m HCl-0.5m MgCl -0.5m C u C l ) 2  2  JJV|?|B[B|I|'-'1 SCAN: 40.0/100.0/0.05/1.5(sec), Cu[40kV,20rrA), l{max)«1199.02/03/06 02:2 <40.00-1QO.0Q> f"~ P D F P CPS l ~ 28(0) |0.0  jj  |  Overlaid patterns  -u a JO +-> c  TO  c  JS  ItUlal'H  | t | t | i\ : | B | X | - j :||008-0090> Pentlandite-|Fe,Ni)3S8  [1B5-0.05CuCI2.tawI 1B5-6m HCI-0_lj_?l  rx3  C  JL8  —  C  Residue  c ai  _2 5 CL  Pentlandite • (Fe.Ni)9S8 Pyrrhotite-4H-Fe1-xS C TJ C 03  ®  CL  T3 C 03  TJO  cr:  —  £= JO  Feed  Q) Q.  a  (DO)  \L4 40  X! C 03  50  60  70  80  90  100  96  Table 4.18 Contents of low M g O concentrate leach residue (6m HCl-0.5m MgCl -0.5m CuCl atl00°C) 2  2  lB5-6.05-0.5CuCl, ID on SEM Image  I  wt. fraction of elements based on SEM-EDX S  Si  0  Fe  Ni  Mg  wt. fraction of elements and calculated minerals based on SEM-EDX Sum  O  FeS  Ni  Mg Si 0,„(OH)  Cu  Sum  Overall  0.266 0.126 0.328 0.119 0.044 0.050 0.057 0.991 0.129  0.131  0.113  0.257  0.044  0.260  0.057  0.991  Area 1 Area 2 Area 3 Area 4  0.267 0.267 0.268 0.268  0.136 0.143 0.143 0.143  0.115 0.114 0.113 0.111  0.247 0.249 0.250 0.249  0.042 0.042 0.043 0.041  0.258 0.252 0.254 0.253  0.059 0.056 0.055 0.063  0.992 0.991 0.992 0.995  4.4.6  0.127 0.128 0.128 0.128  0.332 0.333 0.332 0.330  0.115 0.116 0.117 0.116  0.042 0.042 0.043 0.041  0.050 0.049 0.049 0.049  Cu 0.059 0.056 0.055 0.063  0.992 0.991 0.992 0.995  S 0.135 0.134 0.134 0.135  Si0  2  2  3  4  2  High M g O concentrate and its leach residue  Major peaks on the X-ray patterns o f the high M g O concentrate feed (Figure 4.42) were identified as pentlandite. The middle pattern on this figure corresponds to the solid residue o f this sample, where high metal extractions were obtained i n the mixture o f 6m H C l and 2m M g C l no additions o f either C u C l  2  2  with  or F e C b . A s a result o f high metal extractions, pentlantite peaks  disappeared i n the leach residue pattern. The residue was then subjected to S E M for further investigation.  97  Figure 4. 42 X-ray patterns of high M g O concentrate and its leach residue (6m H C l and 2m M g C l atlOO°C) 2  * I v I ? I B | B| 11 -1 SCAN: 40.0/'80.0/0.05/1.5(scc), Cu[40kV.20irA), Umax).3980,02/03/06 03:07p  u  r  PDF r CPS  r zm |o.o jj g gj  Overlaid patterns  V *>j(^£fri 1  [3B5-6.2-1 law] 3B5-6.2-1 • Ganbol l | "I  a  M - | + l "I • I « H  •I 121 "' Jg ro  - I B| x |-r | jj|0QB-0090> Pentlandite • [Fe.Ni)9S8  a>o>  m J)  j  ?| - M -'I »l " 1 » 1 i | g | x  a) t_  _5>0)  itfcl  a) «B r  2<¥j Residue  Pentlandite - (Fe.Ni)9S8 Millerite - NiS Quartz-Si02  0^-  Pictures taken from S E M - E D X are shown below. The overall picture displays mostly fine, black-colored particles with a few white particles (Figure 4.43 and Figure 4.44). Figure 4. 43 100°C)  S E M image of high M g O concentrate leach residue (6m H C l and 2m M g C l at 2  98  Figure 4. 44  S E M image of high M g O concentrate leach residue: Selected spots  Based on the X R D and S E M - E D X analyses, the compositions o f the leach residue were determined for the selected spots on Figure 4.44 and tabulated below. Table 4.19 100°C)  Compositions of high M g O concentrate leach residues (6m HCl-2m M g C l at 2  Spots  weight fraction as Fe  S  Si  O  Cu  Ni  Co  Mg  Si0  SUM 2  Overal  0.063 0.082  ~  0.143 0.000 0.055 0.006 0.054  0.601  1.003  Areal  0.008 0.013  —  0.055 0.000 0.000 0.000 0.015  0.907  0.998  SpotlW  0.243 0.340  0.093  0.997  0.951  0.989  0.934  1.000  -  --  0.000 0.310 0.000 0.012 Spot2D 0.010 0.020 ~ 0.000 0.000 0.000 0.009 Spot3D 0.000 0.022 0.036 0.000 0.000 0.000 0.009 Note: — Stochiometric amount of either Si or O presents. Accounted in S i 0 . 2  According to this table, the leach residue mostly consists o f quartz. Spotl (a few white dots on overall picture) represents un-leached nickel minerals. A minor amount o f iron, sulfur and magnesium was reported in the residue. The X R D , S E M - E D X results were very consistent to the dissolution results reported in section 4.3.2. Leaching results with the addition o f C u C l are reported i n Figure 4.22. To address the low 2  recoveries, the leach residue was subjected to S E M - E D X . The addition o f 0.05m C u C l has resulted 2  in the lowest metal recoveries. Major peaks on the X-ray pattern o f the leach residue were identified as pentlandite (the middle pattern on Figure 4.45). Note that major peaks o f the feed were identified as pentlandite.  99  Figure 4. 45 X-ray patterns of high M g O concentrate and its leach residue (6m HCl-2m MgCl -0.05m C u C l at 100°C) 2  :)  2  r P D F r C P S r swiloo  J I $ | ? j B j B | 11 -• I SCAN: 40.0/80.0/0.05/1.5(sec). Cu(40kV,20ftA), l[max)>3980,02/03/06 03:07p  U w =J  II  Overlaid patterns  4i [3B 5-6.2-005CuD2-60\raw] 3B 5-6. i i i ?  )+(<»! 11 11 J I : | B | X H ;l|073-0515> Pentlandite-Ni4.5Fe4.5S8 0> :  5  i S  5 «J to Residue Q.Q.I  3 T  Millerite-NiS Pentlandite • Ni4.5Fe4.5S8  Feed  5  <D (J)  U 1 40  Figure 4. 46  50  60  S E M image of high M g O concentrate: (6m HCl-2m MgCl -0.05m C u C l at 100°C) 2  2  Table 4. 20 Compositions of high M g O concentrate leach residue (6m HCl-2m MgCl2-0.05m CuCl atl00°C) 2  3B5-6.2-0.05CuCI  2  |  wt. fraction of elements based on SEM-EDX  o  (CoFeNi),S  0.165 0.135 0.392 0.104 0.149 0.047 0.008 0.998 0.100  0.170  0.161  0.325  0.242  0.998  Area 1  0.168 0.135 0.383 0.104 0.153 0.048 0.007 0.999 0.102  0.165  0.152  0.330  0.250  0.999  Area 2 Area 3 Area 4  0.171 0.137 0.385 0.109 0.148 0.048 0.006 1.003 0.106 0.172 0.139 0.382 0.107 0.153 0.048 0.009 1.010 0.106 0.174 0.139 0.384 0.110 0.152 0.048 0.007 1.014 0.107  0.169 0.174 0.176  0.151 0.145 0.147  0.328 0.336 0.336  0.249 0.250 0.248  1.003 1.010 1.014  s  Si  o  wt. fraction of elements and calculated minerals  Overall  ID on SEM Image  Fe  Ni  Mg  Co  Sum  S  Si0  2  8  Mg Si O, (OH) 3  4  0  2  Sum  S E M image o f this leach residue displays white and black particles (Figure 4.46), however, all these color variations show exactly the same composition (Table 4.20). S E M - E D X based assays did not show copper enrichment like i n low M g O concentrate leaching with the addition o f 0.5m C u C l (Table 4.18). Instead, excess sulfur (or its compounds and variations) was found. In addition, 2  an excess amount o f oxygen was detected. These two may have contributed to the result o f the low metal dissolutions. The additions o f 0.2m C u C l  2  or 0.2m FeCi3 have resulted i n higher metal  extractions than the previous case. However, these tests d i d not get higher metal extractions comparable to the results obtained with no additions o f either C u C l  2  or FeCl3. The S E M images  (Figure 4.47 and 4.48) and the calculated compositions o f the corresponding leach residues (Table 4.21 and 4.22) are shown below, with the addition o f C u C l and FeCi3, respectively. In both cases, 2  the results showed similar compositions with excess amount o f sulfur and oxygen. From the tabulated results, the reasons o f the lower metal extractions with the addition o f these salts are the same; formation o f excess elemental sulfur is believed to be the main reason. The formation o f excess elemental sulfur with the addition o f cupric ion is unknown. The formation o f excess elemental sulfur with the addition o f ferric was predicted i n section 2.2.6b ( R X N 2.3). The ferric reduction by the H S gas to the ferrous sulfide and elemental sulfur is highly 2  favorable. Therefore, the ferric ion would not promote metal extractions i n the presence o f reducing agents such as hydrogen sulfide gas, which is the reaction product o f base metal sulfides by the direct attack o f acid.  101  Figure 4. 47  S E M image of high M g O concentrate leach residue: (6m HCl-2m MgCl -0.2m CuCl atl00°C) 2  2  Table 4. 21 Compositions of high M g O concentrate leach residue: (6m HCI-2m MgCl -0.2m CuCl atl00°C) 2  2  3B5-6.2-0.2CuCl  2  I  wt. Fraction of elements based on SEM-EDX  wt.fractionof elements and calculated minerals  s  Si0  0.222 0.156 0.309 0.106 0.161 0.033 0.011 0.999  0.153  0.284  Area 1  0.222 0.155 0.311 0.106 0.162 0.035 0.009 1.000  0.153  Area 2 Area 3  0.223 0.154 0.310 0.107 0.163 0.034 0.009 1.000 0.217 0.154 0.313 0.107 0.162 0.034 0.012 0.999  0.153 0.147  ID on SEM Image Overall  S  Si  O  Fe  Ni  Mg  Co  Sum  O  (CoFeNi) S  0.042  0.348  0.173  0.999  0.274  0.046  0.346  0.180  1.000  0.276  0.046  0.349  0.176  0.278  0.049  0.351  0.173  1.000 0.999  2  9  s  Mg,Si O, (OH) 4  0  2  Figure 4. 48 Compositions of high M g O concentrate leach residue (6m HCl-2m MgCl -0.2m FeCl a t l 0 0 ° C ) 2  3  102  Sum  Table 4. 22 Compositions of high M g O concentrate leach residue: (6m HCl-2m MgCl2-0.2m FeCl a t ! 0 0 ° C ) 3  3B5-6.2-0.2FeCl  wt. fraction of elements based on S E M - E D X  3  ID on S E M Image  S  Si  0  Fe  Ni  Mg  Co  wt. fraction of elements and calculated minerals Sum  S  Si0  2  Overall  0.214 0.137 0.284 0.132 0.185 0.034 0.012 0.999  0.132  0.229  Area 1  0.214 0.140 0.278 0.131 0.186 0.035 0.013 0.998  0.132  Area 2  0.214 0.139 0.285 0.132 0.183 0.033 0.013 0.999  0.133  4.4.7  O  (CoFeNi) S 9  Mg Si O (OH)  g  3  4  l0  Sum  2  0.049  0.41 1  0.17S  0.999  0.232  0.038  0.412  0.183  0.998  0.237  0.047  0.409  0.172  0.999  Nickel matte and its leach residue  The X-ray patterns o f the matte sample and a leach residue are shown i n Figure 4.49. The matte sample mostly consists o f heazlewoodite mineral as seen on its X R D pattern. The X-ray patterns o f the leach residue, where the highest metal extractions were obtained, did not match to elemental sulfur. Nevertheless, they match to a mineral named suredaite with a chemical composition o f C u A s S 9 . Further, the leach residue o f matte sample was investigated by S E M 6  4  E D X . The S E M images are shown in Figures 4.50-4.51. Figure 4. 49 X-ray patterns for matte and its leach residue (6m HCl-2m M g C l at 100°C) 2  roline)  J | i j ? | B] Bl 11 -1 SCAN: 40.0/80.0/0.05/15(sec), Cu(40kV,20mM. I(mai<)*337-102/03/06 0J53p  I~ PDF l~ CPS f~ 2W110.0  M =1  103  F i g u r e 4. 50  S E M picture of matte leaching residue (6m H C I - 2 m M g C l at 100°C)  F i g u r e 4. 51  S E M picture of matte leaching residue: Selected spots  2  A calculated mineral composition based on the S E M - E D X results is shown i n Table 4.23 and is consistent with the X R D peaks. The S E M and E D X analysis proved that the residue contains about 60% o f the suredaite in addition to about 20% o f elemental sulfur.  104  The insolubility o f suredaite i n the leach solution was the reason o f low copper extraction from this matte sample. The main component o f the matte is heazelwoodite, and is dissolved i n strong acid solution forming H2S and H2 gases as discussed in section 2.2.6a. Both gases are strong reducing agents, especially on cupric ion ( R X N 2.2 and R X N 2.4 i n section 2.2.6b). Therefore, the dissolved copper was reduced and resulted in the low copper extraction. Note that copper i n suredaite is in cuprous form, indivating that this compound may have been formed in the process o f cupric reduction. Instantly, it may be possible selectively leach nickel from arsenic i n matte using the non-oxidative leach system. Table 4. 23  Matte leaching solid residue compositions  Spots  Weight percent as  Suredaite  Overall  S 0.222  Si. 0.003  Cu 0.097  Ni 0.027  Areal Spotl  0.268 0.864  0.002 0.000  0.104 0.037  0.024 0.000  Spot2  0.226  0.075  0.079  0.024  Note:  —  As accounted in  SUM  As  CU6AS4S9  -  0.631  0.980  0.584 0.099  0.982 1.000  0.564  0.968  —  —  CU6AsS9 4  Overall, leaching results o f matte is properly explained by thermodynamic predictions as discussed i n section 2.2.6 and supported by X R D , S E M - E D X analysis.  4.5  Summary of commercial concentrates leaching and X R D , S E M analyses  The mixture o f magnesium chloride and hydrochloric acid solutions have proven their suitability to leach most o f the base metal sulfides, nickel sulfide concentrates and matte samples at atmospheric pressure. Temperature plays a key role on the dissolution and kinetics. A n acceptable dissolution was achieved at higher temperatures just below the boiling point (~100°C) o f the strong brine mixture. The dissolution results o f individual mineral leaching proved the possibilities and leach conditions for the commercial sulfide products. T w o sulfide concentrates and a matte sample supplied by B H P Billiton were studied here. The low M g O concentrate was slower to leach than the high M g O concentrate i n this specific mixture. The low M g O yielded about 95% metal extractions i n a mixture o f 8m H C l and 2m M g C l for two hours o f leaching time; whereas the high M g O concentrate yielded same extractions 2  in a mixture o f 6m H C l - 2 m M g C k for an hour o f leaching time. The leach temperature i n both cases was 100°C. Under above mentioned leach conditions, the magnesium dissolution was 63% and  105  83%, with no additions o f either ferric or cupric chloride salts, for the leaching o f low and high M g O concentrates, respectively. The dissolved magnesia could be recycled by the pyrohydrolysis. The leach residue o f low M g O concentrate contained mostly pyrite, talc and quartz. A substantial amount o f pentlandite and pyrhotite o f the feed disappeared as a result o f leaching, meaning that these minerals are leachable i n a strong brine mixture at this temperature. The leach residue o f the high M g O concentrate, where the highest metal extractions were occurred, contained mostly quartz and talc. Note that this feed contained mostly pentlandite. Therefore, it confirms that the pentlandite from this concentrate is leachable in this mixture at these conditions. The addition o f either Q1CI2 or F e C h did not promote metal dissolution. The addition o f 0.5m either salts to leach solutions o f low M g O concentrate resulted i n lower metal extractions due to formation o f copper and elemental sulfur on the particle surfaces. The formation o f copper and sulfur enriched layers is predicted thermodynamically, and confirmed by X R D , S E M - E D X results. Similarly, the additions o f these salts, to leach solutions o f high M g O concentrate, did not result in an improved recovery due to formation o f excess sulfur product on the surface o f minerals. The explanation o f the decreased metal extractions wwas provided by the thermodynamics o f the metal cations i n this mixture as discussed in section 2.2.6. In this case, the formation o f elemental sulfur with the addition o f the ferric ion is well defined, whilst sulfur formation with the addition o f cupric ion is unknown. On the other hand, close to 99% metal extractions were obtained from the nickel matte i n mixtures with acid concentration o f as low as 3m within an hour o f retention time. However, 6m H C l i n mixture is preferred in order to leach copper values i n the feed. The leached matte residue contains quartz and sulfur as final products, i n addition to a mineral named suredaite. L o w extractions o f copper from matte were expected i n section 2.2.6, and the test results confirmed this. Overall, the mixture o f H C l - M g C l 2 was proven to be a good lixiviant for the processing o f sulfide products at atmospheric pressure.  H i g h dissolution o f metals can be obtained i n a mixture  with a strong acid concentration at higher temperature or just below the boiling point o f the mixture.  106  C H A P T E R 5 CONCLUSIONS AND RECCOMMENDATIONS  5.1  Conclusions  The aim o f this work was to study leaching chemistry o f sulfide minerals and commercial products in the mixture o f H C l and M g C ^ . A s part o f this study, thermodynamics o f this mixture were studied. Based on the thermodynamic calculations and experimental results, the following conclusions are drawn:  a) K n o w n experimental methods to measure activity coefficients o f species i n the mixture of H C l and M g C b are difficult to apply for strong solutions at higher temperatures. Therefore, only a calculation method provides an estimation o f activity coefficients o f ions in solutions with higher ionic strength and at higher temperatures. In this thesis, the calculations involved the Meissner's method for mean activity coefficients o f compounds in this mixture, followed by assigning individual ion activity coefficients applying Bate's equation and the modified Jansz's equations for mixed electrolytes. Furthermore, p H values o f any mixtures were estimated based on these calculations. b) Based on the solubility measurements o f MgCh  i n hydrochloric solutions, following  findings are concluded: A n increasing temperature resulted i n an increased solubility, whereas an increasing acid concentration resulted i n a decreased solubility o f MgCl2The solubility limits o f M g C k in water were determined 485.6 and 557 g/1 at 22 and 82.5°C, respectively. These limits decreased to 243 and 452 g/1 i n 6m acid solutions at 22 and 82.5°C, respectively. c) The temperature plays an important role for the dissolution o f sulfide minerals in this mixture. Based on the initial leaching results, 100°C or just below the boiling point o f the solutions has resulted in the highest metal extractions. d) A c i d concentration i n the mixture o f H C l and M g C b plays an important role in the increased dissolution o f individual sulfide minerals and commercial sulfide concentrates along with temperature. O n the other hand, an increasing concentration o f M g C L ; in the mixture o f H C l and M g C ^ has no significant effect on increased metal recovery. L o w M g O concentrate could yield about 95% metal extractions in mixtures with 2m MgCl2 and 8m H C l within 2 hours o f leaching. The high M g O concentrate could yield over 95% metal recoveries in mixtures with 2m M g C L ; and 6m H C l within 1 hour o f leaching. The  107  dissolution o f magnesia were 63% for low M g O , and 83% for high M g O concentrates. N i c k e l matte could yield over 99% metal recoveries i n mixtures with 2m M g C l and 6m 2  H C l within 1 hour o f leaching. The matte is leachable even at lower acid concentration, i f copper extraction is not required. The tendency o f cupric reduction by reaction product gases caused the low copper extractions from matte, e) The addition o f C u C l or FeCh in the leach solutions o f commercial concentrates had no 2  beneficial effects on the increased metal recoveries. Based on the S E M and E D X o f the solid residues, the following reasons explained the low metal extractions. The cupric and ferric ions are easily reduced by the sulfide mineral dissolution gases such as H S and 2  H . The reduced products are more likely to cover mineral surfaces resulting i n lower 2  metal extractions. The ferric reduction, to ferrous sulfide and elemental sulfur by H S 2  gas, is highly favorable ( R X N 2.3 with AG°=-203kJ/mol). The ferrous sulfide may dissolve instantly i n a strong acid solution at high temperature; therefore, elemental sulfur caused decreased metal extractions. The S E M and E D X analysis o f solid residues of low and high M g O concentrates with the addition o f ferric chlorides confirmed that the low extraction was caused by ferric reduction.  5.2  Recommendations  Further studies need to focus on the following aspects: a) The activity coefficient measurement o f this mixture at high ionic strength and high temperature should be considered from the point o f view o f physical chemists. More precise measuring devices and instruments are recommended for this purpose. b) Further studies are recommended to address low recoveries with the addition o f C u C l  2  and FeCl3. Alternative methods (besides X R D , S E M - E D X i n this work) should be applied to identify species formed on the surface o f the leach residue. c)  Continuous, or batch wise two-stages o f leaching tests are recommended to get high metal extractions while not increasing retention time.  d) The development o f complete flowsheets including leaching, solid-liquid separation, solution  purification, iron  removal, product  recovery  and  reagent  recycling is  recommended to establish full mass flow o f the circuits.  108  U . S . Geological survey. (2006). Mineral Commodity Summaries: N i c k e l . Retrieved January 10, 2006, from http://minerals.er.usgs. gov/minerals/ D a l v i , A . D . , Bacon, W . G . , & Osborne, R . C . (March 7-10, 2004). The past and the future o f nickel laterites. P D A C International Retrieved January 10, 2006, from  Convention, Trade Show & Investors Exchange.  http://www.minmet.mcgill.ca/teachingresources.nsf/  Peters, E . (1976). Direct leaching o f sulfides: chemistry and applications. Metallurgical Transactions B , V o l . 7 B , 505-517. Peters, E . (1977). Applications o f chloride hydrometallurgy to treatment o f sulfide minerals. Proceeding o f Chloride Metallurgy, (pp. 1-37). Brussels: Benelux metallurgie. Dreisinger, D . B . (2004). N e w developments  i n hydrometallurgical treatment o f copper  concentrates. Engineering & M i n i n g Journal, 205(5), 32-36. D i x o n , D . G . (1997). Chloride based leaching o f sulfides: principles and practice. Vancouver: A short course note for the Industrial Research Chair in Hydrometallurgy at the University o f British Columbia. Jansz, J.J.C. (1984). Chloride hydrometallurgy for pyritic zinc-lead sulfide ores: The nonoxidative leaching route. Helmond: Wibro. Habashi, F. (Ed.). (1997). Handbook o f extractive metallurgy. V o l . 2. Weinheim. Chichester: Wiley-VCH. Habashi, F. (1997). The hydrometallurgy o f nickel sulfides. In Cooper, W . 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Presented at the Industrial  Research  Chair Meeting i n Hydrometallurgy at the University o f British  Columbia.  115  Appendix 1  Certificates of analysis  !Certificate#:06A0140 [Sample Name Pentlandite Troilite Millerite Heazelwoodite Violarite Chalcopyrute Pyrite  - -j SampleType Pulp Pulp Pulp Pulp Pulp Pulp Pulp  Minimum detection Maximum detection Method Sample Name Pentlandite Troilite Millerite Heazelwoodite Violarite Chalcopyrute Pyrite  Cu  %  %  30.41 34.59 32.81 4.50 33.39 33.29 54.06  3.22 8.69 0.53 0.15 0.45 35.78 0.04  SampleType  Minimum detection Maximum detection Method  %  4.077 0.288 59.528 10.538 19.256 0.292 <0.001  Co)  Fei  %  %  0.108 0.060 0.260 0.328 0.345 0.004 0.067  63.461 57.477 13.799 15.170 36.933 34.100 51.559  Pulp Pulp Pulp Pulp Pulp Pulp Pulp  SampleType Pulp Pulp Pulp Pulp Pulp Pulp Pulp  All ppmi 521' 1308 473 16960 411 <100 248  Sb ppm: <5 <5 <5 <5! <5 <5 <5  As ppm 42 161 528 190 176 <5 "<5  Ba ppm 26 75 <2 <2 <2 28 63  Bi ppm <2 <2 <2 <2 <2 <2 <2  Cd ppm: <0.2 <0.2 79.6 47.7 <0.2 <0.2 <0.2  5 2000 ICPM;  5 10000 ICPM  2 10000 ICPM  2 2000 ICPM  0.2 2000 ICPM  100 100000 ICPM  Ni ppm 40686 2669 592924 104800 190346 2843 62  PEE 108 283 <100 5660 <100 1386 <100  PP 988 532 2437 2992 3231 27 580  Cu! ppm 32155 86795 5236 1422 4342 353000 366^  Fe ppm 630117 572265 137817 151224 368952 337513 499627  La ppm <2 <2 <2 3 <2 <2 <2  Pb ppm <2 <2 1252 153 <2 110 <2  Mg ppm <100 4116 254 170352 3312 <100 <100  Mn ppm 816 29 21 492 488 39 17  Hg ppm <3 <3 <3 <3 <3 <3 <3  Mo ppm 15 11 12 1295 18 8 11  1 10000 ICPM  1 10000 ICPM  1 20000! ICPM  100 50000 ICPM  2 10000 ICPM '  2 10000 ICPMI  100! 100000! ICPM  1 10000 ICPM  3 10000 ICPM  1 1000 ICPM  1 10000! ICPM!  Na ppm 191 436 180 181 1196 211 211  Sr ppm <1 <1 <1 10 3 <1 <1  Tl ppm <2 <2 <2 <2 <2 <2 <2  Ti ppm 136 <100 <100 <100 <100 <100! <100  W ppm <5 <5 <5 <5 <5 <5 18  V ppm 79 54 17 57 39 27 41  Zn ppm 581 837 <1 <1 <1 3457 115  Zr! ppm! 6! 3 <1 <1 <1 <1 3  100 100000 ICPM  1 10000 ICPM  2 1000 ICPM  100 100000 ICPM:  5 1000 ICPM  1 10000 ICPM  1 10000 ICPM  Co m  K  Sc  As  PP <100 <100 <100 <100 <100 <100 <100  PP" <1 2 1 3 <1 4 <1  Ppm 83 55 10.1! <0.5[ 4.0! 171.9! <0.5  100 100000 ICPM  1 ioooo ICPM  1  0.5 500 ICPM  Ca ppm 204 179 871 12475 3537 <100 244  100 50000 ICPM  Cr ppm 6 778 7 722 116 4 77  m  Pentlandite Troilite Millerite Heazelwoodite Violarite Chalcopyrute Pyrite  Nii  0.01 0.01 0.001 0.001 0.001 100 100 100 100 100 Leco AsyMuA AsyMuA i AsyMuA AsyMuA  Minimum detection Maximum detection Method Sample Name  S(tot)  1 10000 ICPM  P  100 50000 ICPM  Certificated: 06B0204 BHP Billiton Sample IDSample NamSampleTyj  S(tot)  Al ppm  As ppml  Cd ppm  Ca ppm  Cr ppm  Co ppm  Cu! ppm i  Fe ppm  Pb ppm  Mg ppm  29.92 29.45 20.23 20.31 24.74 24.66 25.15 24.49  1092 1029 1443 1460 0i 0! 0 0  129! 151 599 654 753 777 767 S26  0.0 0.0 ' 2.8 4.5 95.9 102.9 96.2 97.8 '  2044 2000 2026 2026 443 430 432 434  153 149 281 • 268 10 5 7 5  2790 2840 6789 6802 10196 10189 10207 10222  3229! 3387! 1213! 1064! 23250! 23693! 23467! 23494!  384907 390965 211921 209288 54752 55132 55753 56497  0 0 15 33 256 247 246 249  45466 43038 93310 94141 303 197 267 247  0.01 100 Leco  100 50000 ICPM  5 10000 ICPM  0.2 2000 ICPM  100 100000 ICPM  1 10000 ICPM  1 10000 ICPM  1! 20000! ICPM  100 50000 ICPM  2 10000 ICPM  100 100000 ICPM  Sample Nam SampleTyp  Mn  ,  P.P  Mo ppm  Ni ppm;  Ag ppm  Na ppm  Sr ppm  W ppm  V ppm  324 316 609 610 5 5 6 6  21: 22! 16 16 29 32 40 31  134989 135300 257509 255486 741993 738702 747857 747528^  0.0 0.0 0.0 0.0 11.2 9.8 10.4 12.8  956 989 921 908 854 867 896  12 11 5 6 0 0 0 0  0 0 0 0 346 368 397 388  17 18 13 12 10 9: 10 9  1 10000 ICPM  1 1000 ICPM  1 10000 ICPM!  0.5 500 ICPM  100 100000 ICPM  1 10000 ICPM  5 1000 ICPM  1 10000 ICPM  %  FL UF FCCL Low MgQ BHP-1 FLUFFCCLLowMgO BHP-2 Sample 2 High MgQ.l BHP-3 Sample 2 High MgO.2 BHP-4 Mattel BHP-5 Matte 2 BHP-6 Matte3 BHP-7 Matte 4 BHP-8  Pulp Pulp Pulp Pulp Pulp Pulp Pulp Pulp  Minimum detection Maximum detection Method  BHP-1 BHP-2 BHP-3 BHP-4 BHP-5 BHP-6 BHP-7 BHP-8  £ulp Pulp Pulp Pulp Pulp Pulp Pulp Pulp  Minimum detection Maximum detection Method  m  ;  Zn ppm 93 93 618 629 0 0 0 0 1 10000 ICPM  -  Certificated:  06A0139  Sample Name  SampleType  SI S2 S3 S 4.1 S4.2 S5.1 S5.2 S5.3 So" S7 S8.1 S8.2 S9 S10 Sll S12 S14 S15 316 S17 S19 S20 S22 S23 S24 S25  Solution Solution Solution Solution Solution Solution Solution Solution Solution Solution Solution Solution Solution Solution Solution Solution Solution Solution Solution Solution Solution Solution Solution Solution Solution Solution  Clmg/L  Fe mg/L  Mg mg/L  Al mg/L  Sb mg/L  As mg/L  Ba mg/L  Bi mg/L  9746.8 7995.0 7799.5 7207.7 7078.7 6863.7 6771.5 6761.5 9583.1 8741.2 7701.9 7922.6 7401.6 6758.3 8863.1 8435.0 7708.8 7340.3 8422.7 9346.7 7733.0 7500.5 5988.8 6809.5 7252.2 7613.2  —  1342.24 2120.17 2417.01 2654.11 2604.87 2753.17 2819.03 2772.03 1873.31 2416.86 2764.24 2739.76 2856.25 2836.21 2295.77 2709.14 3004.86 3099.53 2383.41 3056.97 3140.34 3141.32 2482.95 2891.48 2997.93 3219.09  <0.2 <0.2 <0.2 0.4 0.2 <0.2 <0.2 <0.2 <0.2 <0.2 <0.2 <0.2 0.2 0.2 <0.2 <0.2 1.1 0.5 <0.2 <0.2 <0.2 <0.2 <0.2 <0.2 0.2 <0.2  0.3 O.l 0.1 0.2 0.2 0.1 <0.1 <0.1 0.3 0.5 0.3 0.6 0.2 0.3 0.6 0.6 0.3 0.4 1.0 1.0 0.3 0.3 0.2 0.3 0.3 0.3  0.2; <0.2 <0.2 <0.2 <0.2 0.2 <0.2 <0.2 0.2 <0.2 <0.2 <0.2 <0.2 <0.2 <0.2 <0.2 <0.2 0.2 0.4  0.01 0.04 0.04 0.04 1.74 0.02 0.02 0.05 0.06 0.03 0.04 0.01 0.02 <0.01 <0.01 <0.01 0.15 0.06 <0.01 <0.01 0.02 0.02 0.02 0.02 0.02 0.02  O.l <0.1 O.l O.l <0.1 <0.1 O.l <0.1 <0.1 <0.1 <0.1  — —  -  —  —  —  -  —  — — —  -  -  — ~  — — — — — — — —  <02  <0.2 <0.2 0.2 0.2 0.2 <0.2  <0.1 <0.1 O.l O.l <0.1 O.l <0.1 <0.1 <0.1 O.l O.l <0.1 O.l O.l  Cd mg/L O.01 : O.011 <0.01 O01! <0.01 <0.01 <0.01 <0.01 <0.01 O.011 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 ' ' <0.01 <0.01 <0.01 <0.01 <0.01! <0.01  Ca mg/L  Cr mg/L  Co mg/L  0.3 0.8 1.1 0.5 0.4 0.4 0.3 0.3 0.5 0.4 0.4 0.4 0.2  6.46 0.81 0.55 O.01 <0.01 <0.01 O.01 <0.01 9.59 15.80 9.31 10.05 O.01 <0.01 50.27 48.40 0.05 O.01 101.87 62.25 0.15 0.07 <0.01 <0.01 O.01 <0.01  0.17 0.09 0.10 0.05 0.08 0.08 0.06 0.05 0.19 0.31 0.24 0.20 <0.01 0.05 0.59 0.81 0.09 0.06 1.13 1.02 0.06 <0.01 0.06 0.08 0.06 0.01  ~02  0.4 0.4 1.4 0.7 1.1 0.3 0.4 0.4 0.4 0.2 0.9 0.3  Certificated:  06A0139  continues  Sample Name  Cu mg/L  Fe mg/L  La mg/L  Pb mg/L  Mg mg/L  Mn mg/L  Hgi mg/L  Mo mg/L  Ni mg/L  P mg/Li  K mg/L  Sc mg/L  Ag mg/L  SI S2 S3 S4.1 S4.2 S5.1 S5.2 S5.3 S6 S7 S8.1 S8.2 S9 S10 Sll S12 S14 S15 S16 S17 S19 S20 S22 S23 S24 S25  0.21 0.17 0.14 <0.01 <0.01 <0.01 <0.01 <0.01 0.26 0.27 0.20 0.26 <0.01 <0.01 0.65 0.53 <0.01 <0.01 1.23 0.60 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01  28.03 3.82 3.31 <0.03 <0.03 <0.03 <0.03 <0.03 39.93 65.73 39.13 42.11 <0.03 <0.03 205.23 196.85 1.77 <0.03 456.45 257.48 0.79 <0.03 <0.03 <0.03 <0.03 <0.03  0.11 0.17 0.13 0.13 0.12 0.15 0.15 0.11 0.13 0.15 0.15 0.17 0.11 0.12 0.14 0.12 0.12 0.09 0.11 0.06 0.08 0.10 0.06 0.10 0.09 0.08  <0.05 0.41 0.47 <0.05 0.53 0.50 0.29 0.38 0.48 0.50 0.57 0.33 <0.05 0.47 0.36 <0.05 0.45 <0.05 0.24 0.28 0.32 0.46 <0.05 <0.05 <0.05 0.53  1366.8 2211.6 2515.1 2715.4 2688.6 2860.3 2867.6 2837.7 1965.3 2481.7 2797.3 2782.6 2888.7 2920.3 2333.4 2755.1 3005.5 3102.4 2406.3 3067.4 3132.4 3143.0 2552.9 2898.2 3034.8 3202.2  0.59 0.08 0.07 <0.01 <0.01 <0.01 <0.01 <0.01 0.74 1.25 0.73 0.78 <0.01 <0.01 3.59 3.77 0.09 0.04 7.80 4.92 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01  <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 <005 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05  0.20 0.17 0.23 0.26 0.22 0.33 0.21 0.22 0.25 0.23 0.29 0.25 0.22 0.21 1.18 0.49 0.17 0.22 2.71 0.50 0.20 0.25 0.17 0.21 0.15 0.20  "3.25 0.45 0.24 <0.02 <0.02 <0.02 <0.02 <0.02 5.13 7.65 4.84 4.98 <0.02 <0.02 31.75 23.92 <0.02 <0.02 75.80 30.58 <0.02 <0.02 <0.02 <0.02 <0.02 <0.02  1.4 18 1.9 0.4! 1.7 1.0 1.0 1.6 0.7 2.3 0.9 1.8 2.9 2.6 2.1 1.8 2.8 2.3 2.3 2.6 1.7 2.8 1.2 3.8! 3.1! 1.4  <2 13 <2 14 14 12 <2 <2 12 13 17 14 <2 <2 <2 <2 <2 <2 <2 <2 <2 <2 <2 <2 52 <2  0.03 0.01 0.01 0.01 <0.01 <0.01 0.01 0.01 0.01 <0.01 <0.01 0.01 0.01 0.01 0.01 0.01 0.02 0.01 0.01 0.01 <0.01 0.01 0.01 0.01 0.01 0.01  <0.02 0.15 <0.02 <0.02 <0.02 <0.02 <0.02 <0.02 0.08! <0.02 <0.02 <0.02 <0.02 0.07 <0.02 <0.02 <0.02 <0.02 <0.02 <0.02 O.02 <0.02 <0.02 <0.02 <0.02 <0.02  1  Certificated: Sample Name  S1 S2 S3 S4.1 S4.2 S5.1 S5.2 S5.3 S6 S7 S8.1 S8.2 S9 S10 Sll S12 S14 S15 S16 S17 S19 S20 S22 S23 S24 S25  06A0139  continues  Na mg/L  Sr mg/L  Tl mg/L  Ti mg/L  W mg/L  V mg/L  Zn mg/L  Zr mg/L  <1 2 2 2 2 3 2 2 2 2 2 2 2 2 2 2 1 <1 <1 <1 <1 <1 <1 <1 <1 <1  <0.01 <0.01 O.01 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 <o.oi <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01  <0.2 <0.2 <0.2 <0.2 <0.2 <0.2 <0.2 <0.2 <0.2  7.3 2.4 2.4 <0.1 <0.1 <0.1 <0.1 <0.1 6.0 31.0 20.7 22.7 0.1 <0.1 12.8 120.5 <0.1 <0.1 19.9 163.0 0.2 <0.1 <0.1 <0.1 <0.1 <0.1  <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1j <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1  0.11 <0.01 <0.01 <0.01 <0.01 <0.01 O.01 <0.01 0.10 0.17 0.06 0.14 <0.01 <0.01 0.24 0.36 0.07 0.07 0.54 0.51 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01  0.04 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 0.05 <0.01 <0.01 <0.01 <0.01 0.06 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 O.01 4.59 <0.01  0.45 0.31 0.28 0.19 0.26 0.03 0.07 <0.01 0.38 0.49 0.33 0.34 0.27 0.03 0.40 0.85 0.32 0.18 0.36 1.10 0.50 0.46 0.41 0.03 <0.01 0.05  J  <02 <02  <0.2 <0.2 <Q2  <0.2 <02  <0.2 <0.2 <0.2 <0.2 <0.2 <0.2 <0.2 <0.2 <0.2 <0.2  Sample NaiSampleTyf  Heazelwoo Pulp Violarite Pulp 1BHP Pulp 3BHP Pulp REHeazelv Repeat Minimum detection Maximum detection Method  Si02  MgO  %  %  23.78 1.31 9.01 11.76 23.84 0.01 100 WRock  „  8.76 17.37  0.01 100 WRock  Certificated: 06E1246 Sample Name  SampleType  1B5-8.2-1 1B5-8.2-2 3B5-6.2-02CuC12-60" 3B5-6.2-02FeC13-60' RE 1B5-8.2-1  Solution Solution Solution Solution Repeat  Minimum detection Maximum detection Method  Al mg/L  Sb mg/L  As mg/L  Ba mg/L  Bi mg/L  Cd mg/L  Ca mg/L  Cr mg/L  Co mg/L  Cu mg/L  Fe mg/L  La mg/L  2.5 6.3 13.1 14.2 2.4  <0.1 O.l O.l O.l O.l  0.2 0.6 2 0.2 0.3  O.01 O.01 O.01 O.01 O.01  O.l O.l O.l O.l O.l  O.01 O.01 O.01 O.01 O.01  11.5 21.6 23 23.1 11.6  0.33 0.81 2.71 2.9 0.34  11.29 21.7 17.9 12.92 11.4  7.27 16.23 2686.74 3.24 7.45  1813.44 3561.01 1217.36 3600.89 1828.87  O.05 O.05 O.05 O.05 O.05  0.1 0.2 9999 9999 ICPH20 ICPH20  0.01 999 ICPH20  0.1 9999 ICPH20  0.01 999 ICPH20  0.1 9999 ICPH20  0.01 9999 ICPH20  0.01 9999 ICPH20  0.01 9999 ICPH20  0.03 9999 ICPH20  0.05 999 ICPH20  0.2 9999 ICPH20  Sample Name  SampleType  Pb mg/L  Mg mg/L  Mn mg/L  Hg mg/L  Mo mg/L  Ni mg/L  P mg/L  K mg/L  Sc mg/L  Ag mg/L  Na mg/L  Sr mg/L  1B5-8.2-1 1B5-8.2-2 3B5-6.2-02CuC12-6'u3B5-6.2-02FeC13-60' RE1B5-8.2-1  Solution Solution Solution Solution Repeat  0.31 0.69 0.56 0.73 <0.05  5202.7 10280.2 10852.2 11037.8 5139.1  1.47 2.85 5.93 15.21 1.48  O.05 O.05 O.05 O.05 O.05  0.16 0.33 0.26 0.23 0.24  655.27 1364.83 994.19 903.36 656.25  O.l 1.1 O.l O.l O.l  <2 <2 <2 <2 <2  O.01 O.01 0.04 O.01 O.01  O.02 O.02 O.02 O.02 O.02  <1 <1 <1 <1 <1  0.07 0.08 O.01 O.01 0.07  0.05 9999 ICPH20  0.1 9999 ICPH20  0.01 999 ICPH20  0.02 0.1 9999 9999 ICPH20 ICPH20  2 9999 ICPH20  0.01 100 ICPH20  0.02 999 ICPH20  Tl mg/L  Ti mg/L  W mg/L  V mg/L  Zn mg/L  Zr mg/L  <0.2 <0.2 <0.2 <0.2 <0.2  0.3 0.5 0.8 0.7 03  O.l O.l O.l O.l O.l  O.01 0.13 0.11 0.14 O.01  0.46 0.72 5.18 7.01 0.47  O.01 0.03 0.02 0.05 O.01  0.2 999 ICPH20  0.1 999 ICPH20  0.01 999 ICPH20  0.01 9999 ICPH20  0.01 999 ICPH20  Minimum detection Maximum detection Method Sample Name  SampleType  1B5-8.2-1 1B5-8.2-2 3B5-6.2-02CuC12-60" 3B5-6.2-02FeC13-60* RE 1B5-8.2-1  Solution Solution Solution Solution Repeat  Minimum detection Maximum detection Method  0.1 9999 ICPH20  0.05 0.02 9999 9999 ICPH20 ICPH20  1 0.01 9999 999 ICPH20 ICPH20  Certificated: 06E1138 Sample Name  SampleType  1B5-2.2-100-4 1B5-6.2-100-4 1B5-6.2-100-2 C5-7.2-100-4 3B5-4.2-02CuC12-20" 3B5-4.2-02FeC13-20 3B5-4.2-02CuC12-60' 3B5-4.2-02FeC13-60" FeC13 CuC12 RE1B5-2.2-100-4  Solution Solution Solution Solution Solution Solution Solution Solution Solution Solution Repeat  -  Minimum detection Maximum detection Method Sample Name  SampleType  1B5-2.2-100-4 1B5-6.2-100-4 1B5-6.2-100-2 C5-7.2-100-4 3B5-4.2-02CuC12-20" 3B5-4.2-02FeCB-203B5-4.2-02CuC12-60' 3B5-4.2-02FeC13-60FeC13 CuC12 RE1B5-2.2-100-4  Solution Solution Solution Solution Solution Solution Solution Solution Solution Solution Repeat  Minimum detection Maximum detection Method  Fe mg/L  Cu mg/L  —  —  --  -  -  —  —  —  -  -  -  59400  -  61000.00  Al mg/L  Sb mg/L  As mg/L  Ba mg/L  Bi mg/L  Cd mg/L  Ca mg/L  Cr mg/L  Co mg/L  Cu mg/L  28.8 7 3.3 0.4 5.9 5.9 13.5 13.9  <0.1 <0.1 <0.1 0.1 <0.1 <0.1 <0.1 <0.1  <0.2 <0.2 <0.2 <0.2 1.2 0.7 0.5 0.6  0.55 <0.01 <0.01 0.04 <0.01 <0.01 <0.01 <0.01  <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1  <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01  109.2 23.2 12.2 33.8 12.4 12.1 23.5 23.3  3.57 0.85 0.4 <0.01 1.32 1.36 2.76 2.81  3.66 15.42 6.22 0.23 8.45 2.99 16.3 9.5  18.25 15.76 6.73 841.78 1141.03 4.94 2278 6.98  —  —  —  —  „  -_  —  -  —  —  —  ._  „  __  ._  __  ..  -  29.0  <0.1  <0.2  0.58  <0.1  <0.01  109.9  3.62  3.75  0.03 0.01 9999 9999 AA H20 AA H20  0.2 9999 ICPH20  0.1 9999 ICPH20  0.2 9999 ICPH20  0.01 999 ICPH20  0.1 9999 ICPH20  0.01 999 ICPH20  0.1 9999 ICPH20  0.01 9999 ICPH20  0.01 9999 ICPH20  —  __  19.33 0.01 9999 ICPH20  Fe mg/L  La mg/L  Pb mg/L  Mg mg/L  Mn mg/L  Hg mg/L  Mo mg/L  Ni mg/L  P mg/L  K mg/L  Sc mg/L  Ag mg/L  12031.82 3216.01 1519.2 824.32 534.52 1587.5 1161.72 3339.32  O.05 0.13 0.16 <0.05 0.25 0.1 0.07 <0.05  <0.05 0.44 0.24 1.9 0.78 0.45 0.79 0.26  51381.9 10417 5291.1 48605.4 5399.2 5155.4 10574.2 10585.7  12.68 2.9 1.51 0.18 3 7.66 6.03 15.28  <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05  0.6 0.53 0.23 0.45 0.32 0.2 0.33 0.43  469.8 972.17 379.48 24.39 442.01 165.22 918 597.4  <0.1 <0.1 1.4 <0.1 <0.1 2 <0.1 <0.1 ._  <2 16 15 <2 20 <2 <2 <2 .. __  <0.01 <0.01 0.01 0.02 0.01 <0.01 0.05 0.01 __  0.06 <0.02 <0.02 1-51 <0.02 <0.02 <0.02 <0.02  --  -  -  12240.61  O.05  0.03 9999 ICPH20  0.05 999 ICPH20  — —  <0.05  -  —  52017.6  —  —  —  —  —  —  __  __  ._  12.78  <0.05  0.83  477.32  <0.1  <2  <0.01  0.05 0.1 0.01 9999 9999 999 ICPH20 ICPH20 ICPH20  0.05 9999 ICPH20  0.02 9999 ICPH20  0.02 9999 ICPH20  0.1 9999 ICPH20  2 9999 ICPH20  0.01 100 ICPH20  0.06 0.02 999 ICPH20  Certificated: 06E1 138  continues Na mg/L  1B5-2.2-100-4 :lB5-6.2-100-4 1B5-6.2-100-2 C5-7.2-100-4 3B5-4.2-02CuC12-20' 3B5-4.2-02FeC13-20" 3B5-4.2-02CuC12-60 3B5-4.2-02FeC13-60 FeC13 CuC12 RE 1B5-2.2-100-4 -  >  Solution Solution Solution Solution Solution Solution Solution Solution Solution Solution Repeat  7 5 5 3 5 5 5 5  Sr mg/L  Tl mg/L  Ti mg/L  0.46 <0.2 2.2 0.091 0.2 0.6 <0.01 < 0 . 2 ' " 0 . 4 0.09 <0.2| <01 <0.01 <0.2 0.4 <0.01 <0.2 0.3 <0.01 0.2 0.9 <0.01 <0.2 0.7 :  W mg/L  V mg/L  Zn mg/L  Zr mg/L  O.l O.l O.l O.l O.l O.l O.l O.l  0.68 0.18 0.11 O.01 0.07 0.09 0.12 0.17  9722 0.93 0.63 25.89 1.92 3.68 3.6 7.07  0.171 0~05 0 03 0.06 O.01 O.01 0.03 O.01  -7  -  -  0.50  -  -  0.2  2.2  1 9999 ICPH20  0.01 999 ICPH20  0.2 999 ICPH20  0.1 999 ICPH20  Al mg/L  Sb mg/L  As mg/L  Ba mg/L  Bi mg/L  Cd mg/L  Ca mg/L  Cr: mg/L!  Co mg/L  Cu mg/L  Fe mg/L  La mg/L  Pb me/L  Mg ms/L  <0.2 <0.2 <0.2 0.2 <0.2  0.3 0.3 0.3 0.4 0.4  <0 2 0.2 <0.2 <0.2 <0.2  O01 0.01 0.05 0.01 <0.01  O.l O.l O.l O.l O.l  O.01 O.01 O.01 0.25 O.01  3.8 3.3 3.1 19 4.1  O.01! O.01; O.01 O.01 O.01  O.01 O.01 O.01 O.01 O.01  34.2 70.33 73.68 73.69 37.74  77.12 152.4 166.58 188.24 78.63  O.05 O.05 O.05! 0.06 O.05  1.91 1.86 1.98 2.04 1.94  69262 7 51320.5 30932.2 11501 70762.2  0.2 9999 ICPH20  0.1 9999 ICPH20  Minimum detection Maximum detection Method  -  -  O.l  — —  0.72  0.1 0.01 9999 999 ICPH20 ICPH20  __  ._ 9.25  __  _. 0.21 -  0.011 0.01 9999: 999 ICPH20 ICPH20  Certificated: 06E0997 Sample Name  C4-1-3.5 C4-3-2.5 C4-5-1.5 C4-7-0.5 RE C4-1-3.5 Minimum detection Maximum detection Method Sample Name  C4-1-3.5 C4-3-2.5 C4-5-1.5 C4-7-0.5 REC4-1-3 5 Minimum detection Maximum detection Method  Mn mgrt0.13 0.16 0.15 0.19 0.14 0.01 999 ICPH20  Hg  0.2 9999 ICPH20  0.01 999 ICPH20  0.1 9999 ICPH20  0.01 999 ICPH20  0.1 9999 ICPH20  0.01 9999 ICPH20  0.01 9999 ICPH20  0.01 9999 ICPH20  0.03 9999 ICPH20  0.05 999 ICPH20  0.05 9999 ICPH20  0.1 9999 ICPH20 Zr mg/L  .g5r.  Mo I mg/L  Ni mg/L  P mg/L  K mg/L  Sc mg/L  Ag mg/L  Na mg/L  Tl mg/L  Ti mg/L  W mg/L  Zn mg/L  <0.05 <0.05 <0.05 <0.05 O.05  0.39 0.51 0.4 0.27: 0.36 i  0.93 3.27 3.96 4.49 1.01  O.l O.l O.l 1.1 O.l  <2 <2 <2 <2 <2  0.02 0.01 0.01 0.02 0.01  0.1 0.25 0.37 0.48 0.1:  7 6 6 6 7  0.2 0.2 0.2 0.2 0.2  O.l O.l O.l O.l O.l  O.l O.l O.l O.l O.l  9.2 17.19 22.6 27.35 9.45  0.05 0.02 0.02: 0.1 9999 9999! 9999 9999 ICPH20I ICPH20! ICPH20! ICPH20  2 9999 ICPH20  0.01 100 ICPH20  0 02 1 999: 9999 ICPH20 ICPH20  0.2 999 ICPH20  m  0.1 999 ICPH20  0.1 """9999 ICPH20  0.01 9999' ICPH20  1.38 1.6 1.04 0.4 1.38 0.01 999 ICPH20  g 4> U.  g  g  o O  Vi vo o o o o V V vo co Os o  VO CD O V  VO CD o CD d V V  Os 00 vo O vo vd vo vb vo Os Os 00 CN vo CO 00 CO 00  $  CD "st co vo CN vo co o>' vo vs. CN 00 CN cn CO  9 o  00  g  00  Os o c-^ Os  00  CN  CN os vb vo CO  <1  CD  vo o CD V  VO O CD V  CN vo vq 00 CN vo  vo o CD V  CN  VO P CD V  CO 00  00  oo Os CN CO  VO vo 0 0 r-; CO t-^ vb vb CO VO Os CN CN 00  ^  00  vo Os O p Os CD Os CN X  a N  PL,  g  VO VO •^r 0 0 vo CN  vo CN VO Os Os CO vq VQ •o CN CN CD vd CN CO  g  OS CO VO vq p CD CN CO CD  Os vo CN VO  CO O CD  o  Os Os Os Os CN X a, o  >  g  CL,  o o  d  CO  CD d CD V  VO o ^q CD CD  Os p Os O CN CD Os Os X Cu O Os O Os CD Os  V,  g  00 cn o o CN CN CO  CN  CN CO p CN  OS CD  CD o V V  O V  o V  o V  O V  o V  o V  o V  ac CU  H  CN  X  o  VO CO CO CN 00  g  CN  CN CO  CO CD  CN CO  00  CD CO  Os Os CD Os  P  CN  X  g  •a  O  3  VO Os VO CO vb vo vo  Os CO CN CO Os CN f-v Os Os  Os Os CD Os Os  o 8  w  CL,  g  CN CN CN CN CD CD CD d V V V V  CN  CO  Os  d V  g  p o V  p o V  p p CD d V V  p O O CD CD d V V V  p O CD CD V V  g  o V  o V  o V  o V  CD O V V  •i g  < i  g  JO Vi  <  •A  p o V  p CD CD V  CN CN CD d V V  CN CN CD CD V V  o V  o V  o V  o  00  CD CD d  VD  o  p p CD CD d V V V  P p CD CD V V  Os O Os CD Os  X  S  CN  X  u o CN  00  O CD d V  V  g  CN  o  00  vb CN  o V  •o o  vp VO  00 CO  vb  Os CD  o V  o V  o V  o V  O V  00  •n  Os  °0  VO  (N  00  Os 0 0 vb vb CN  o  s  O CD CD V  Os O Os CD Os  o V  o V  CD V  Os O CD Os Os CN Os DC  OD  o o  CN Os CD Os Os CN Os X Cu o  CN  a o o  Os Os Os CN Os X cu  V  O  o  g  *T VO vo •<* Os CN CN CN od 00 CD $ VO CO CN vo OS  CO *q vb vo CD CN CN  CO VO vo CO CN OS  CN CD CD  Os Os Os CN Os X Cu O  •i g  Os VO vo 00 vp vq VO vq CD CD d CD CD  00 vo vq CD CD CD CD  CN p CD  Os O Os Os CN Os X Cu  VO O CD V  VO O CD  Os O Os Os CN Os X Cu o  •i g  C  s  0H  CN VO CN "O Os 00 »-> vb •O VO  O  9  i  ^  o  o  Os O CD Os Os CN Os X Cu O CS  X  CL,  oPH Os CD Os Os Os  CN  CN OS O CD Os Os CN X Cu O  CL,  00  g  CD  CO CO VO CO  PL,  PQ  O  o Os O Os CD Os  o o Cu O  PL,  o •a g  PC  Os O CD Os Os CN Os  PL,  Os O Os CD Os Os  CN  CL,  O o  O O  Os O Os O CN CD Os Os X  Os O Os CD Os Os  vo  Os Os Os  ICPH20  s  0.01  N  O  Os CO CO o oo  VO vo OS VO CN CN o CN CO CO CO  Os Os Os Os  <0.01 0.08 0.57 0.75 <0.01 <0.01 0.03 O.01 <0.01  o  ICPH20  Os CO  00  3 O  00 00  0.05  CN  2.88 0.39 0.94 0.36  g  i  1.98 1.92  PH  s  2  VO p CD V  VO O CD V  VO O CD V  VO p od CD V V  VO O CD V  VO O CD V  vo p CD V  CO CN 00 Os vo [--; vq O 0 0 0 0 00 vo «o CN CN »o »o' VO vb CN CN CN CN CO  Os O Os O CD Os CN  Os 00 CN CD r-. Os vo CN VO  Os CD Os Os Os  o  s  00  vb CN c-CN  Os CO VO CO VO vb vb Os CD CO CN CN 00 vo CO  o  3'  ac 0H o o  CN  ac PH  o  a c a  1 o  to CN vo  S  z  u  o  w|  a  G o  C o  C o  c  1 I 1 I 111 O  o  o Vi  o o o to d oin d NO VO vo vo  d  tZ  VO O 5tt  o CO  O  o  O o CO in  a  o to o vo  m  s  m  O  OH  o oto vo  O VO CD CD CN vb VO PQ  CO  H a>  <u O. a>  d a a o  o o CD VO a> o O vo vo VO tu « l o o CD CD VO •o vo vo d O o CN O o vo VO vd P vb CN CD vo vo VO vd VO CN vb PQ PQ •A vb CO CO CO vo PQ vo PQ CO CO  (6  ft  d »A o vd vA PQ CO  s  c c o  w  a  a)  1 1 •o o  55 4>  a  s  a>  OT|  C  O  c o  c  1 o  G o  c c  O  O  "S3  I 1 1 w 1 1 1 ft!  o o vo  a  C O O o V u <1> "8  o  o d vo  |  o Vi o d Vi d VO  a  O  wo &  a d  o o a> U. U.  O o o Vi O CO VO VO  CD d vo o O vo o «o VO <$• vo d CD d d o vA vo vA •A CD CN O o o o vd vb vd vd CN vd CN •A \b •A vo •o vb PQ vo PJ PQ CO CO VO CO PQ CO PQ CO  (6  i i  2  m  d d u"i  o vo o CD CN vb 1 vo  CQ  CO  d vA o vd v~» PQ  C O  •j* o  S3 O  •a 4> ~* 4>  •o o  CO  S  Appendix 2  Summary of thermodynamic calculations  Table A 2 . 1 Best fit equation* values for lnynci & lnyM ci2 for integral part o f the osmotic coefficient g  calculation n  aj  3i  s  MgCl  HCl -0.007 0.085 -0.005 -0.306 0.007  3.000 2.000 1.000 0.000 0.000  2  3.506 2.253 1.388 0.062 0.000  -0.013 0.002 0.645 -0.888 0.033  y where rrij molal of species j , e.g. H C l or M g C l . ±  2  Table A 2 . 2 Comparative table o f calculated osmotic coefficient and mean ionic activity coefficient values against reference [42] values for pure H C l or pure M g C b electrolyte at 2 5 ° C .  m  MgCl  0.1 0.2 0.3 0.4  0.861 0.877 0.895 0.919  0.755  r± HCl MgCl HCl CALCULATED VALUES 0.837 0.995 0.502 0.788 0.895 0.986 0.466 0.754 0.914 0.979 0.464 0.740 0.934 0.976 0.476 0.735  0.5  0.947  0.974  0.480  0.757  0.958  0.978  0.495  0.735  0.6 0.7  0.976 1.004  0.986 0.998  0.490 0.505  0.763 0.772  0.986 1.017  0.983 0.991  0.520 0.549  0.739 0.746  0.8 0.9 1 1.2 1.4 1.6  1.036 1.071 1.108 1.184 1.264 1.347  1.011 1.025 1.039 1.067 1.096 1.126  0.521 0.543 0.569 0.630 0.708 0.802  0.783 0.795 0.809 0.840 0.876 0.916  1.048 1.079 1.111 1.176 1.247 1.329  1.001 1.012 1.024 1.052 1.083 1.116  0.581 0.616 0.654 0.739 0.841 0.966  0.755 0.766 0.778 0.808 0.843 0.883  1.8  1.434  1.157  0.914  0.960  1.419  1.150  1.120  0.928  2 2.5 3 3.5 4 4.5 5 5.5 6  1.523 1.762 2.010 2.264 2.521 2.783 3.048  1.188 1.266 1.348 1.431 1.517 1.598 1.680 1.763 1.845  1.051 1.538 2.320 3.550 5.530 8.720 13.920  1.009 1.147 1.316 1.518 1.765 2.040 2.380 2.770 3.220  1.517 1.769 2.023 2.275 2.527 2.783 3.043  1.185 1.273 1.360 1.445 1.532 1.622 1.717 1.817 1.920  1.307 1.926 2.812 4.046 5.734 8.001 10.997 14.900 19.917  0.977 1.120 1.293 1.500 1.751 2.059 2.439 2.907 3.475  —  -  2  r± HCl MgCl REFERENCE VALUES 0.943 0.528 0.945 0.488 0.952 0.476 0.963 0.474 2  4>  HCl 0.796 0.767 0.756  MgCl  2  2  126  Table A 2 . 3 Calculated mean ionic activity coefficients o f H C l ( ^  ± ( / / c / )  ) in mixture o f H C l - M g C k  compared with reference values Temp  25.0 °C Temp 35.0 °C Temp 45.0 °C Calc.D Calc. J Reff[43] Calc.D Calc. J Calc.D Calc. J MRC12 Reff[43] MgC12 MRCL2 Reff [43] Calc.D and Calc.J - applied approaches described in Dixon [61 and Jansz [71, Meisner [31-381 papers, respectively TX ltntnl Ulal  Y  Y  Y  0.10  0.000  -0.097  -0.103  -0.103  0.000  -0.099  -0.103  -0.103  0.000  -0.101  -0.103  -0.103  0.10 0.10 0.10 0.10 0.25 0.25 0.25 0.25 0.50 0.50 0.50 0.50 0.50 0.50 1.50 1.50 1.50 1.50 1.50 1.50 2.00 2.00 2.00 2.00 2.00 2.00 2.50 2.50 2.50 2.50 2.50 2.50 3.00 3.00 3.00 3.00 3.00 3.50  0.313 0.508 0.765 0.870 0.000 0.499 0.640 0.872 0.000 0.101 0.360 0.504 0.671 0.886 0.000 0.138 0.250 0.477 0.768 0.919 0.000 0.129 0.251 0.501 0.758 0.841 0.000 0.086 0.297 0.509 0.713 0.889 0.000 0.355 0.517 0.771 0.826 0.000  -0.098 -0.108 -0.099 -0.111 -0.100 -0.114 -0.101 -0.116 -0.120 -0.128 -0.125 -0.139 -0.126 -0.142 -0.129 -0.148 -0.122 -0.134 -0.125 -0.137 -0.128 -0.146 -0.132 -0.150 -0.135 -0.156 -0.140 -0.163 -0.048 -0.064 -0.058 -0.074 -0.064 -0.082 -0.081 ' -0.098 -0.100 --0.119 -0.112 -0.130 0.004 -0.010 -0.006 -0.022 -0.019 -0.034 -0.042 -0.057 -0.064 -0.081 -0.072 -0.089 0.059 0.049 0.050 0.039 0.027 0.014 0.003 -0.011 -0.018 -0.035 -0.041 -0.056 0.119 0.112 0.071 0.061 0.051 0.037 0.014 0.001 0.006 -0.007 0.181 0.176  -0.105 -0.106 -0.107 -0.107 -0.128 -0.132 -0.133 -0.135 -0.134 -0.136 -0.140 -0.142 -0.144 -0.147 -0.064 -0.072 -0.078 -0.089 -0.100 -0.106 -0.010 -0.020 -0.029 -0.046 -0.060 -0.064 0.049 0.040 0.020 0.002 -0.013 -0.025 0.112 0.069 0.052 0.028 0.024 0.176  0.155 0.508 0.765 0.870 0.000 0.331 0.499 0.872 0.000 0.101 0.360 0.504 0.671 0.886 0.000 0.138 0.250 0.477 0.768 0.919 0.000 0.129 0.251 0.501 0.758 0.841 0.000 0.086 0.297 0.509 0.713 0.889 0.000 0.355 0.517 0.771 0.826 0.000  -0.100 -0.102 -0.103 -0.103 -0.123 -0.126 -0.127 -0.131 -0.126 -0.128 -0.133 -0.136 -0.139 -0.143 -0.055 -0.065 -0.072 -0.088 -0.108 -0.120 -0.009 -0.020 -0.031 -0.055 -0.079 -0.080 0.046 0.035 0.013 -0.012 -0.034 -0.055 0.109  -0.104 -0.106 -0.107 -0.107 -0.128 -0.132 -0.133 -0.136 -0.135 -0.137 -0.142 -0.144 -0.146 -0.149 -0.071 -0.079 -0.085 -0.096 -0.107 -0.113 -0.021 -0.031 -0.040 -0.056 -0.070 -0.074 0.034 0.026 0.006 -0.011 -0.026 -0.038 0.092 0.051 0.035 0.012 0.008 0.152  0.155 0.313 0.508 0.870 0.000 0.331 0.499 0.872 0.000 0.101 0.360 0.504 0.671 0.886 0.000 0.138 0.250 0.477 0.768 0.919 0.000 0.129 0.251 0.501 0.758 0.841 0.000 0.086 0.297 0.509 0.713 0.889 0.000 0.355 0.517 0.771 0.826 0.000  -0.102 -0.103 -0.104 -0.106 -0.126 -0.129 -0.131 -0.135 -0.130 -0.133 -0.137 -0.141 -0.144 -0.148 -0.063 -0.072 -0.080 -0.098 -0.115 -0.126 -0.020 -0.032 -0.043 -0.068 -0.085 -0.100 0.028 0.019 -0.005 -0.028  0.036 0.001 -0.007 0.160  -0.105 -0.111 -0.115 -0.116 -0.128 -0.136 -0.140 -0.149 -0.135 -0.138 -0.147 -0.152 -0.158 -0.165 -0.071 -0.081 -0.089 -0.105 -0.126 -0.137 -0.021 -0.033 -0.044 -0.067 -0.091 -0.099 0.034 0.025 0.000 -0.024 -0.048 -0.068 0.092 0.043 0.021 -0.015 -0.022 0.152  0.021 -0.018 -0.022 0.138  -0.105 -0.108 -0.111 -0.117 -0.128 -0.136 -0.141 -0.150 -0.136 -0.140 -0.149 -0.154 -0.160 -0.168 -0.078 -0.088 -0.096 -0.112 -0.133 -0.144 -0.031 -0.043 -0.054 -0.077 -0.100 -0.108 0.020 0.010 -0.013 -0.037 -0.060 -0.080 0.073 0.026 0.004 -0.030 -0.037 0.129  -0.104 -0.105 -0.106 -0.108 -0.128 -0.132 -0.134 -0.137 -0.136 -0.138 -0.143 -0.146 -0.149 -0.152 -0.078 -0.086 -0.092 -0.102 -0.114 -0.120 -0.031 -0.041 -0.050 -0.066 -0.080 -0.084 0.020 0.011 -0.008 -0.025 -0.039 -0.050 0.073 0.034 0.018 -0.004 -0.008 0.129  3.50 3.50 3.50 3.50 4.00 4.00 4.00 4.00  0.092 0.513 0.717 0.857 0.000 0.509 0.617 0.783  0.167 0.102 0.063 0.044 0.252 0.158 0.141 0.106  0.160 0.089 0.054 0.030 0.243 0.143 0.121 0.089  0.161 0.104 0.081 0.067 0.243 0.159 0.144 0.123  0.092 0.513 0.717 0.857 0.000 0.509 0.617 0.783  0.144 0.082 0.048 0.030 0.231 0.133 0.112 0.087  0.137 0.069 0.035 0.012 0.215 0.119 0.098 0.067  0.138 0.084 0.062 0.048 0.215 0.135 0.120 0.100  0.092 0.513 0.717 0.857 0.000 0.509 0.617 0.783  0.127 0.062 0.037 0.015 0.208 0.109 0.092 0.063  0.114 0.049 0.017 -0.005 0.186 0.095 0.076 0.046  0.115 0.063 0.042 0.029 0.186 0.111 0.097 0.078  4.00  0.857  0.093  0.074  0.114  0.857  0.068  0.053  0.092  0.857  0.033  0.070  -0.070 0.093  127  Table A2.3 Continues 4.50  0.000  0.306  0.314  0.314  0.000  0.280  0.280  0.280  0.000  0.258  0.247  0.247  4.50  0.389  0.228  0.226  0.236  0.389  0.206  0.196  0.207  0.389  0.184  0.168  0.178  4.50 4.50 4.50 5.00 5.00 5.00 5.00 5.00  0.501 0.640 0.783 0.000 0.284 0.520 0.647 0.829  0.205 0.179 0.148 0.377 0.315 0.261 0.231 0.189  0.200 0.169 0.137 0.387 0.315 0.254 0.222 0.175  0.217 0.195 0.174 0.387 0.321 0.274 0.251 0.221  0.501 0.640 0.783 0.000 0.284 0.520 0.647 0.829  0.180 0.155 0.129 0.364 0.296 0.235 0.205 0.167  0.172 0.142 0.112 0.348 0.279 0.222 0.192 0.148  0.189 0.168 0.148 0.348 0.285 0.241 0.220 0.191  0.501 0.640 0.783 0.000 0.284 0.520 0.647 0.829  0.158 0.135 0.107 0.343 0.272  0.145 0.117 0.088 0.310 0.245 0.191 0.162 0.121  0.161 0.141 0.123 0.310 0.251 0.210 0.189 0.163  6.00 6.00 6.00 6.00 6.00 6.00 6.00 6.00 9.00 9.00 9.00 9.00 9.00 9.00 9.00 9.00  0.000 0.150 0.300 0.450 0.600 0.750 0.900 1.000 0.000 0.150 0.300 0.450 0.600 0.750 0.900 0.970  0.541 0.493 0.446 0.398 0.351 0.303 0.256 0.300 0.993 0.919 0.845 0.771 0.697 0.623 0.549 0.514 25.0  0.541 0.495 0.453 0.415 0.380 0.348 0.318 0.300 0.993 0.920 0.853 0.793 0.737 0.686 0.638 0.618  0.000 0.150 0.300 0.450 0.600 0.750 0.900 1.000 0.000 0.150 0.300 0.450 0.600 0.750 0.900 1.000  0.491 0.446 0.401 0.357 0.312 0.267 0.223 0.265 0.911 0.842 0.773 0.704 0.635 0.566 0.498 0.554 35.0  0.491 0.448 0.408 0.373 0.340 0.310 0.282 0.265 0.911 0.843 0.781 0.725 0.673 0.625 0.582 0.554  0.000 0.150 0.300 0.450 0.600 0.750 0.900 1.000 0.000 0.150 0.300 0.450 0.600 0.750 0.900 1.000  0.442 0.400 0.358 0.316 0.275 0.233 0.191 0.231 0.831 0.768 0.704 0.640 0.576 0.512 0.448 0.501 45.0  0.442 0.402 0.365 0.332 0.301 0.273 0.247 0.231 0.831 0.769 0.711 0.659 0.611 0.567 0.527 0.501  0.184 0.146  Temp Temp Temp °C °C °C Reff [49] Calc.D Calc. J Reff [43] Calc.D Calc. J Reff [43] Calc.D Calc. J MRC12 MgC12 MsC12 Calc.D and Calc.J - applied approaches described in Dixon [6] and Jansz [7], Meisner [31-38] papers, respectively 3.00 0.000 0.119 0.112 0.112 0.000 0.092 0.092 0.000 0.073 0.073 3.00 0.191 0.094 0.084 0.087 0.191 0.066 0.069 0.191 0.048 0.051 3.00 0.411 0.065 0.062 0.411 0.053 0.411 0.035 0.045 0.018 0.028 3.00 0.610 0.039 0.024 0.043 0.610 0.008 0.026 0.610 -0.008 0.010 3.00 0.815 0.010 -0.005 0.025 0.815 -0.021 0.009 0.815 -0.036 -0.007 3.00 0.921 -0.004 -0.021 0.921 0.016 -0.035 0.000 0.921 -0.050 -0.015 2.00 0.000 0.005 -0.010 -0.010 0.000 -0.021 -0.021 0.000 -0.031 -0.031 2.00 0.199 -0.012 -0.029 -0.026 0.199 -0.039 -0.036 0.199 -0.050 -0.046 2.00 0.412 -0.032 -0.049 -0.040 0.412 -0.059 -0.050 0.412 -0.069 -0.060 2.00 0.616 -0.050 -0.068 -0.052 0.616 -0.078 -0.062 0.616 -0.088 -0.072 2.00 0.818 -0.068 -0.087 -0.063 0.818 -0.097 -0.073 0.818 -0.106 -0.083 2.00 0.905 -0.076 -0.095 -0.068 0.905 -0.105 -0.077 0.905 -0.114 -0.087 1.00 0.000 -0.091 -0.109 -0.109 0.000 -0.113 -0.113 0.000 -0.116 -0.116 1.00 0.193 -0.099 -0.119 -0.116 0.193 -0.123 -0.120 0.193 -0.127 -0.124 1.00 0.388 -0.108 -0.129 -0.122 0.388 -0.133 -0.126 0.388 -0.137 -0.130 1.00 0.600 -0.117 -0.140 -0.128 0.600 -0.144 -0.132 0.600 -0.148 -0.136 1.00 0.805 -0.126 -0.150 -0.133 0.805 -0.155 -0.137 0.805 -0.159 -0.142 1.00 0.904 -0.131 -0.155 -0.135 0.904 0.904 -0.160 -0.140 -0.165 -0.144  I total  Y  Y  V  128  Table A 2 . 4 . Calculated mean ionic activity coefficients o f M g C k (y  i)  m  ±MgC 2  mixture o f H C l - M g C b  compared with reference values Temp Temp Temp 45.0 °C 25.0 °C 35.0 °C Reff [43] Calc.D Calc. J Reff [43] Calc.D Calc. J Reff [43] Calc.D Calc. J Y MgCI2 Y MgCL2 MgC12 Calc.D and Calc.J - applied approaches described in Dixon [61 and Jansz [71, Meisner [31-381 papers, resaectively T trvrnl X lUlai  V  0.10  0.000  -0.197  -0.214  -0.214  0.000  -0.202  -0.216  -0.216  0.000  -0.206  -0.217  -0.217  0.10 0.10 0.10 0.10 0.25 0.25 0.25 0.25 0.50 0.50 0.50 0.50 0.50 0.50 1.50 1.50 1.50 1.50 1.50 1.50 2.00 2.00 2.00 2.00 2.00 2.00 2.50 2.50 2.50 2.50 2.50 2.50 3.00 3.00 3.00 3.00 3.00 3.50  0.313 0.508 0.765 0.870 0.000 0.499 0.640 0.872 0.000 0.101 0.360 0.504 0.671 0.886 0.000 0.138 0.250 0.477 0.768 0.919 0.000 0.129 0.251 0.501 0.758 0.841 0.000 0.086 0.297 0.509 0.713 0.889 0.000 0.355 0.517 0.77.1 0.826 0.000  -0.201 -0.203 -0.205 -0.206 -0.240 -0.253 -0.257 -0.263 -0.252 -0.258 -0.272 -0.279 -0.288 -0.298 -0.169 -0.192 -0.210 -0.245 -0.287 -0.308 -0.104 -0.132 -0.157 -0.208 -0.257 -0.272 -0.031 -0.054 -0.108 -0.161 -0.210 -0.250 0.048 -0.061 -0.109 -0.181 -0.196 0.131  -0.231 -0.229 -0.225 -0.224 -0.272 -0.294 -0.293 -0.289 -0.297 -0.333 -0.331 -0.330 -0.328 -0.327 -0.217 -0.276 -0.280 -0.288 -0.297 -0.302 -0.144 -0.216 -0.223 -0.238 -0.254 -0.259 -0.064 -0.145 -0.164 -0.183 -0.201 -0.217 0.019 -0.107 -0.126 -0.157 -0.163 0.106  -0.217 -0.219 -0.221 -0.221 -0.272 -0.281 -0.283 -0.286 -0.297 -0.300 -0.309 -0.313 -0.318 -0.323 -0.217 -0.232 -0.244 -0.265 -0.289 -0.300 -0.144 -0.165 -0.182 -0.215 -0.244 -0.253 -0.064 -0.082 -0.123 -0.159 -0.189 -0.213 0.019 -0.067 -0.100 -0.147 -0.156 0.106  0.155 0.508 0.765 0.870 0.000 0.331 0.499 0.872 0.000 0.101 0.360 0.504 0.671 0.886 0.000 0.138 0.250 0.477 0.768 0.919 0.000 0.129 0.251 0.501 0.758 0.841 0.000 0.086 0.297 0.509 0.713 0.889 0.000 0.355 0.517 0.771 0.826 0.000  -0.205 -0.207 -0.209 -0.210 -0.246 -0.259 -0.263 -0.268 -0.259 -0.265 -0.279 -0.287 -0.295 -0.305 -0.182 -0.205 -0.223 -0.257 -0.299 -0.319 -0.120 -0.147 -0.173 -0.223 -0.271 -0.286 -0.050 -0.073 -0.127 -0.179 -0.226 -0.266 0.025 -0.083 -0.130 -0.200 -0.214 0.104  -0.235 -0.231 -0.228 -0.227 -0.274 -0.300 -0.298 -0.294 -0.301 -0.338 -0.337 -0.336 -0.335 -0.334 -0.231 -0.290 -0.294 -0.302 -0.312 -0.317 -0.164 -0.234 -0.242 -0.256 -0.271 -0.276 -0.089 -0.169 -0.187 -0.205 -0.223 -0.238 -0.011 -0.133 -0.152 -0.181 -0.187 0.069  -0.218 -0.221 -0.223 -0.224 -0.274 -0.282 -0.285 -0.291 -0.301 -0.306 -0.315 -0.320 -0.325 -0.330 -0.231: -0.247 -0.258 -0.280 -0.303 -0.314 -0.164 -0.184 -0.201 -0.234 -0.262 -0.271 -0.089 -0.107 -0.146 -0.181 -0.211 -0.234 -0.011 -0.094 -0.127 -0.172 -0.181 0.069  -0.209 -0.211 -0.214 -0.215 -0.251 -0.265 -0.269 -0.274 -0.266 -0.272 -0.287 -0.294 -0.303 -0.313 -0.192 -0.215 -0.234 -0.269 -0.311 -0.332 -0.132 -0.161 -0.186 -0.237 -0.286 -0.300 -0.066 -0.089 -0.144 -0.196 -0.243 -0.282 0.005 -0.104 -0.151 -0.219 -0.234 0.079  -0.237 -0.235 -0.233 -0.229 -0.277 -0.303 -0.302 -0.299 -0.306 -0.343 -0.342 -0.342 -0.341 -0.340 -0.245 -0.304 -0.308 -0.316 -0.325 -0.331 -0.183 -0.252 -0.260 -0.274 -0.289 -0.293 -0.114 -0.192 -0.209' -0.226 -0.243 -0.258 -0.041 -0.159 -0.177 -0.205 -0.211 0.033  -0.219 -0.221 -0.223 -0.227 -0.277 -0.285 -0.289 -0.295 -0.306 -0.311 -0.321 -0.326 -0.331 -0.337 -0.245 -0.260 -0.272 -0.293 -0.317 -0.328 -0.183 -0.202 -0.220 -0.251 -0.279 -0.288 -0.114 -0.131 -0.169 -0.203 -0.231 -0.254 -0.041 -0.121 -0.152 -0.195 -0.204 0.033  3.50 3.50 3.50 3.50 4.00 4.00 4.00 4.00  0.092 0.513 0.717 0.857 0.000 0.509 0.617 0.783  0.097 -0.049 -0.116 -0.161 0.218 0.015 -0.025 -0.088  -0.002 -0.066 -0.097 -0.118 0.196 -0.003 -0.023 -0.054  0.077 -0.038 -0.084 -0.113 0.196 0.028 -0.002 -0.044  0.092 0.513 0.717 0.857 0.000 0.509 0.617 0.783  0.071 -0.073 -0.138 -0.182 0.186 -0.013 -0.052 -0.111  -0.035 -0.096 -0.125 -0.145 0.153 -0.037 -0.056 -0.085  0.041 -0.068 -0.112 -0.140 0.153 -0.007 -0.035 -0.075  0.155 0.313 0.508 0.870 0.000 0.331 0.499 0.872 0.000 0.101 0.360 0.504 0.671 0.886 0.000 0.138 0.250 0.477 0.768 0.919 0.000 0.129 0.251 0.501 0.758 0.841 0.000 0.086 0.297 0.509 0.713 0.889 0.000 0.355 0.517 0.771 0.826 0.000 0.092 0.513 0.717 0.857 0.000 0.509 0.617 0.783  0.046 -0.098 -0.162 -0.203 0.156 -0.042 -0.080 -0.137  -0.067 -0.125 -0.152 -0.171 0.112 -0.069 -0.087 -0.114  0.007 -0.098 -0.140 -0.166 0.112 -0.040 -0.067 -0.105  4.00  0.857  -0.114  -0.068  -0.062  0.857  -0.137  -0.098  -0.092  0.857  -0.161  -0.126  -0.121  129  Table A2.4 Continues 4.50  0.000  0.308  0.291  0.291  0.000  0.271  0.242  0.242  0.000  0.235  0.194  0.194  4.50  0.389  0.134  0.089  0.136  0.389  0.100  0.050  0.096  0.389  0.064  0.012  0.056  4.50 4.50 4.50 5.00 5.00 5.00 5.00 5.00  0.501 0.640 0.783 0.000 0.284 0.520 0.647 0.829  0.085 0.026 -0.034 0.401 0.259 0.146 0.086 0.002 Temp  0.064 0.034 0.002 0.390 0.190 0.129 0.097 0.050 25.0  0.098 0.054 0.012 . 0.390 0.258 0.163 0.118 0.058  0.501 0.640 0.783 0.000 0.284 0.520 0.647 0.829  0.053 -0.004 -0.061 0.359 0.220 0.110 0.052 -0.027 Temp  0.027 0.059 -0.002 0.018 -0.032 . -0.022 0.334 0.334 0.144 0.209 0.088 0.121 0.057 0.078 0.014 0.021 35.0 °C  0.501 0.640 0.783 0.000 0.284 0.520 0.647 0.829  0.018 -0.036 -0.090 0.315 0.176 0.070 0.016 -0.059 Temp  -0.010 -0.037 -0.064 0.280 0.100 0.048 0.019 -0.021 45.0  0.022 -0.017 -0.055 0.280 0.163 0.079 0.039 -0.014  -0.270 -0.283 -0.298 -0.312 -0.319  -0.323 -0.325 -0.327 -0.329 -0.330  -0.288 -0.300 -0.312 -0.322 -0.327  -0.340 -0.337 -0.335 -0.332 -0.331  0.193 0.388 0.600 0.805 0.904  -0.350 -0.347 -0.344 -0.342 -0.340  -0.343 -0.333 -0.321 -0.307 -0.300  °C °C Reff [49] Calc.D Calc. J Y MRCI2 Reff [43] Calc.D Calc. J Y MgC12 Reff [43] CalcD Calc. J Calc.D and Calc.J - applied approaches described in Dixon [6] and Jansz [7], Meisner [31-38] papers, respectively 3.00 1.000 -0.050 0.019 0.019 -0.207 -0.207 0.000 0.000 -0.230 -0.230 3.00 0.809 -0.075 -0.087 -0.029 0.191 -0.186 -0.178 0.191 -0.209 -0.201 3.00 0.589 -0.111 -0.113 -0.079 0.411 0.411 -0.160 -0.140 -0.185 -0.165 3.00 0.390 -0.151 -0.137 -0.118 0.610 -0.137 -0.102 0.610 -0.163 -0.128 3.00 0.185 -0.198 -0.162 -0.155 -0.114 -0.057 0.815 0.815 -0.141 -0.085 -0.224 -0.175 -0.172 3.00 0.079 0.921 -0.102 -0.031 0.921 -0.129 -0.061 2.00 1.000 -0.169 -0.144 -0.144 0.000 -0.286 -0.286 0.000 -0.303 -0.303 2.00 0.801 -0.192 -0.220 -0.175 0.199 -0.274 -0.267 0.199 -0.291 -0.284 2.00 0.588 -0.218 -0.233 -0.204 0.412 -0.261 -0.244 0.412 -0.279 -0.261 2.00 0.384 -0.246 -0.245 -0.229 0.616 -0.249 -0.219 0.616 -0.267 -0.237 2.00 0.182 -0.275 -0.257 -0.251 0.818 -0.238 -0.192 0.818 -0.256 -0.210 2.00 0.095 -0.288 -0.263 -0.259 0.905 -0.232 -0.179 0.905 -0.251 -0.197 1.00 1.000 -0.256 -0.274 -0.274 0.000 -0.342 -0.342 0.000 -0.352 -0.352  I total  Y M C12 S  1.00 1.00 1.00 1.00 1.00  0.807 0.612 0.400 0.195 0.096  0.193 0.388 0.600 0.805 0.904  -0.333 -0.323 -0.311 -0.298 -0.291  130  Table A 2 . 5 Calculated individual ion activity coefficients for a mixture o f H C l - M g C ^ i n relation to molal concentrations o f each species at 60°C  m HCI  8.00 5.50 3.94 2.00 1.04 10.00 5.01 4.00 1.28 12.00 10.79 7.68 6.00 3.95 1.37 13.00 11.20 9.75 7.00 3.02 1.06 14.00 12.20 10.49 8.00 3.39 2.23 16.00 14.63 11.25 10.00 4.60 3.20 12.90 8.33 6.00 2.95 2.25 13.20 11.98 6.00 3.73 1.89 15.20 8.00 5.83 3.30 2.18  Dixon m  MuC12  0.00 0.83 1.35 2.00 2.32 0.00 1.66 2.00 2.91 0.00 0.40 1.44 2.00 2.68 3.54 0.00 0.60 1.08 2.00 3.33 3.98 0.00 0.60 1.17 2.00 3.54 3.92 0.00 0.46 1.58 2.00 3.80 4.27 0.00 1.52 2.30 3.32 3.55 0.00 0.41 2.40 3.16 3.77 0.00 2.40 3.12 3.97 4.34  I total  8.0 8.0 8.0 8.0 8.0 10.0 10.0 10.0 10.0 12.0 12.0 12.0 12;0 12.0 12.0 13.0 13.0 13.0 13.0 13.0 13.0 14.0 14.0 14.0 14.0 14.0 14.0 16.0 16.0 16.0 16.0 16.0 16.0 12.9 12.9 12.9 12.9 12.9 13.2 13.2 13.2 13.2 13.2 15.2 15.2 15.2 15.2 15.2  n  0.500 0.518 0.561 0.641 0.691 0.380 0.457 0.491 0.611 0.300 0.303 0.341 0.379 0.443 , 0.550 0.280 0.286 • 0.301 0.351 0.477 0.564 0.240 0.246 0.261 0.300 0.429 0.475 0.200 0.2020.228 0.245 0.366 0.412 0.280 0.322 0.375 0.478 0.508 0.280 0.281 0.373 0.444 0.518 0.200 0.292 0.351 0.442 0.492  M8CI2  9.350 9.473 9.748 10.227 10.504 8.470 9.049 9.287 10.052 7.779 7.804 8.147 8.465 8.950 9.678 7.589 7.647 7.785 8.228 9.191 9.767 7.179 7.240 7.400 7.782 8.850 9.178 6.723 6.752 7.051 7.231 8.354 8.722 7.589 7.979 8.429 9.201 9.403 7.589 7.603 8.416 8.959 9.467 6.723 7.701 8.228 8.946 9.293  h HCl  •  yCl-  TEMPERATURE: 60°C 4.494 1.000 2.166 4.578 0.940 1.310 4.767 0.875 1.160 5.103 0.745 1.155 1.221 5.300 0.651 3.907 1.000 3.397 4.291 0.834 1.534 4.451 0.774 1.474 4.980 0.537 1.584 1.000 3.463 5.193 3.479 0.985 3.812 3.697 0.913 2.283 3.903 0.847 1.962 1.821 4.225 0.728 4.719 0.495 2.011 3.344 1.000 6.272 3.380 0.978 4.071 3.467 0.949 3.145 3.750 0.860 2.277 4.386 0.611 2.059 4.781 0.403 2.378 3.091 1.000 7.777 3.128 0.979 5.079 3.227 0.946 3.745 3.465 0.871 2.747 4.157 0.602 2.302 4.378 0.494 2.429 2.816 1.000 11.289 2.834 0.986 8.158 3.013 0.923 4.539 3.123 0.888 3.879 3.831 0.617 2.820 4.073 0.503 2.915 3.344 1.000 6.171 3.590 0.887 2.624 3.880 0.783 2.154 4.393 0.567 2.082 4.530 0.500 2.155 3.344 1.000 6.477 3.353 0.984 4.772 3.872 0.794 2.185 4.230 0.645 2.090 4.574 0.472 2.271 2.816 1.000 10.011 3.414 0.784 3.088 3.750 0.662 2.717 4.222 0.463 2.735 4.455 0.350 2.939  Meisners, Jansz et al. yH+ 11.274 5.382 4.397 2.951 2.286 30.312 9.891 8.313 4.345 76.368 30.330 26.222 21.381 14.922 7.832 120.043 45.197 43.116 33.330 15.935 9.126 179.947 64.046 60.762 49.214 22.417 16.656 403.688 129.545 116.538 105.456 47.928 34.797 114.535 36.847 27.497 14.956 12.455 131.815 48.870 30.332 19.693 12.292 286.480 66.858 48.498 28.544 21.075  •  yCI-  1.017 0.945 0.872 0.725 0.615 1.014 0.842 0.779 0.515 1.025 0.997 0.898 0.818 0.680 0.411 1.032 0.988 0.944 0.828 0.537 0.301 1.030 0.989 0.939 0.842 0.528 0.404 1.029 1.000 0.908 0.862 0.545 0.414 1.023 0.892 0.779 0.542 0.467 1.016 0.989 0.758 0.592 0.399 1.021 0.791 0.663 0.451 0.328  2.089 1.363 1.213 1.195 1.253 3.285 1.607 1.538 1.623 4.993 3.857 2.438 2.105 1.942 2.113 5.992 4.175 3.325 2.460 2.201 2.513 7.468 5.214 3.978 2.974 2.472 2.592 10.879 8.274 4.897 4.221 3.063 3.150 5.939 2.776 2.280 2.174 2.242 6.261 4.843 2.353 2.229 2.396 9.728 3.280 2.863 2.844 3.039  yH+ 11.691 7.281 5.062 3.032 2.282 31.340 11.720 9.202 4.344 79.425 64.992 36.020 25.253 15.609 7.603 125.646 92.869 71.111 41.009 15.841 8.741 187.397 138.862 102.181 63.381 22.319 16.124 418.924 335.395 186.773 148.622 48.427 33.788 119.011 52.293 32.143 15.195 12.433 136.347 111.724 34.620 20.124 11.980 294.815 84.448 53.900 29.012 20.949  131  Table A 2 . 6 Calculated individual ion activity coefficients for a mixture o f H C l - M g C h i n relation to molal concentrations o f each species at 100°C  m  HCl  8.00 5.50 3.94 2.00 1.04 10.00 5.01 4.00 1.28 12.00 10.79 7.68 6.00 3.95 1.37 13.00 11.20 9.75 7.00 3.02 1.06 14.00 12.20 10.49 8.00 3.39 2.23 16.00 14.63 11.25 10.00 4.60 3.20 12.90 8.33 6.00 2.95 2.25 13.20 11.98 6.00 3.73 1.89 15.20 8.00 5.83 3.30 2.18  m  MgC12  0.00 0.83 1.35 2.00 2.32 0.00 1.66 2.00 2.91 0.00 0.40 1.44 2.00 2.68 3.54 0.00 0.60 1.08 2.00 3.33 3.98 0.00 0.60 1.17 2.00 3.54 3.92 0.00 0.46 1.58 2.00 3.80 4.27 0.00 1.52 2.30 3.32 3.55 0.00 0.41 2.40 3.16 3.77 0.00 2.40 3.12 3.97 4.34  I total  8.0 8.0 8.0 8.0 8.0 10.0 10.0 10.0 10.0 12.0 12.0 12.0 12.0 12.0 12.0 13.0 13.0 13.0 13.0 13.0 13.0 14.0 14.0 14.0 14.0 14.0 14.0 16.0 16.0 16.0 16.0 16.0 16.0 12.9 12.9 12.9 12.9 12.9 13.2 13.2 13.2 13.2 13.2 15.2 15.2 15.2 15.2 15.2  a*  0.500 0.518 0.561 0.641 0.691 0.380 0.457 0.491 0.611 0.300 0.303 0.341 0.379 0.443 0.550 0.280 0.286 0.301 0.351 0.477 0.564 0.240 0.246 0.261 0.300 0.429 0.475 0.200 0.202 0.228 0.245 0.366 0.412 0.280 0.322 0.375 0.478 0.508 0.280 0.281 0.373 0.444 0.518 0.200 0.292 0.351 0.442 0.492  Dixon n  MgCI2  9.350 9.473 9.748 10.227 10.504 8.470 9.049 9.287 10.052 7.779 7.804 8.147 8.465 8.950 9.678 7.589 7.647 7.785 8.228 9.191 9.767 7.179 7.240 7.400 7.782 8.850 9.178 6.723 6.752 7.051 7.231 8.354 8.722 7.589 7.979 8.429 9.201 9.403 7.589 7.603 8.416 8.959 9.467 6.723 7.701 8.228 8.946 9.293  n  HCl  •  yCl-  TEMPERATURE: 100°C 4.494 1.000 1.262 4.578 0.957 0.896 4.767 0.912 0.846 5.103 0.824 0.894 5.300 0.760 0.966 3.907 1.000 1.714 4.291 0.885 1.028 4.451 0.845 1.022 4.980 0.686 1.177 2.302 3.463 1.000 3.479 0.990 1.861 3.697 0.941 1.335 3.903 0:897 1.229 4.225 0.818 1.217 4.719 0.663 1.425 3.344 1.000 2.618 3.380 0.985 1.951 3.467 0.966 1.646 3.750 0.906 1.354 4.386 0.740 1.377 4.781 0.603 1.649 3.091 1.000 3.066 3.128 0.985 2.300 0.964 3.227 1.883 3.465 0.913 1.553 4.157 0.735 1.496 4.378 0.664 1.615 2.816 1.000 4.002 2.834 0.991 3.222 3.013 0.949 2.195 3.123 0.925 1.987 3.831 0.746 1.715 4.073 0.671 1.824 3.344 1.000 2.591 3.590 0.923 1.471 3.880 0.853 1.322 4.393 0.710 1.389 4.530 0.665 1.459 3.344 1.000 2.672 3.353 0.989 2.169 3.872 0.861 1.339 4.230 0.763 1.365 4.574 0.648 1.542 2.816 1.000 3.699 3.414 0.855 1.707 3.750 0.774 1.606 4.222 0.642 1.711 4.455 0.568 1.873  Meisners, Jansz et al. yH+  •  4.636 2.705 2.301 1.659 1.341 10.076 4.500 3.924 2.318 20.980 11.057 9.964 8.547 6.470 3.851 30.209 15.433 14.942 12.375 6.987 4.437 41.677 20.537 19.815 17.034 9.358 7.381 80.230 37.032 34.458 32.130 17.943 13.971 29.070 13.276 10.675 6.638 5.729 32.613 16.474 11.610 8.309 5.692 60.411 22.440 17.738 11.787 9.240  1.012 0.962 0.911 0.809 0.733 1.010 0.892 0.849 0.670 1.017 0.998 0.931 0.877 0.785 0.604 1.021 0.992 0.962 0.885 0.690 0.531 1.020 0.992 0.960 0.895 0.685 0.602 1.019 1.000 0.939 0.908 0.697 0.611 1.016 0.928 0.852 0.693 0.642 1.011 0.993 0.838 0.727 0.597 1.014 0.860 0.775 0.634 0.552  yCl1.221 0.921 0.875 0.917 0.985 1.663 1.063 1.054 1.199 2.227 1.870 1.396 1.291 1.274 1.476 2.522 1.979 1.708 1.428 1.443 1.715 2.967 2.336 1.960 1.639 1.572 1.690 3.887 3.244 2.309 2.104 1.816 1.924 2.508 1.528 1.376 1.433 1.501 2.594 2.183 1.410 1.429 1.601 3.613 1.777 1.664 1.758 1.918  yH+ 4.791 3.402 2.569 1.700 1.343 10.385 5.114 4.245 2.322 21.688 18.964 12.530 9.665 6.710 3.778 31.359 25.607 21.295 14.387 6.983 4.311 43.065 35.218 28.539 20.412 9.363 7.234 82.611 71.172 47.812 40.843 18.137 13.728 30.028 17.051 11.972 6.735 5.736 33.593 29.414 12.804 8.470 5.603 61.841 26.492 19.165 11.955 9.219  132  Table A 2 . 7 Effect o f A1C1 , N a C l and C a C l on calculated activity coefficents o f M g C l + H C l mixture at 25 °C 3  Molal concentration of each salt MgCl NaCl A1C13 CaCl 1.0 1.0 0.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 2.0 1.0 1.0 1.0 3.0 1.0 1.0 4.0 1.0 1.0 1.0 1.0 1.0 0.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 2.0 1.0 1.0 1.0 3.0 1.0 1.0 1.0 4.0 1.0 0.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 2.0 1.0 1.0 1.0 3.0 1.0 1.0 1.0 4.0 1.0 1.0 0.0 1.0 1.0 . 1.0 1.0 1.0 1.0 1.0 2.0 1.0 1.0 1.0 3.0 1.0 1.0 1.0 4.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 0.0 1.0 0.0 1.0 0.5 1.0 0.5 1.0 1.0 1.0 1.0 1.0 1.5 1.0 1.5 1.0 2.0 1.0 2.0 1.0 2.5 1.0 2.5 1.0 3.0 1.0 3.0 1.0 3.5 1.0 3.5 1.0 4.0 1.0 4.0 1.0 0.0 1.0 1.0 0.0 0.5 1.0 1.0 0.5 1.0 1.0 1.0 1.0 1.5 1.0 1.0 1.5 2.0 1.0 1.0 2.0 2.5 1.0 1.0 2.5 3.0 1.0 1.0 3.0 3.5 1.0 1.0 3.5 4.0 1.0 1.0 4.0 0.0 0.0 0.0 0.0 1.0 0.0 1.0 0.0 2.0 0.0 2.0 0.0 2.5 0.0 2.5 0.0 3.0 0.0 3.0 0.0 3.5 0.0 3.5 0.0 4.0 0.0 4.0 0.0  HCl 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 0.0 1.0 2.0 3.0 4.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0  2  2  1 total 2  8.0 14.0 20.0 26.0 32.0 11.0 14.0 17.0 20.0 23.0 13.0 14.0 15.0 16.0 17.0 11.0 14.0 17.0 20.0 23.0 13.0 14.0 15.0 16.0 17.0 5.0 9.5 14.0 18.5 23.0 27.5 32.0 36.5 41.0 8.0 11.0 14.0 17.0 20.0 23.0 26.0 29.0 32.0 1.0 10.0 19.0 23.5 28.0 32.5 37.0  HCl 2.771 6.248 12.195 21.419 34.814 3.800 6.248 9.744 14.554 20.972 5.180 6.248 7.484 8.906 10.535 3.580 6.248 10.304 16.203 24.477 0.000 6.248 16.740 33.332 58.467 1.450 3.156 6.248 11.226 18.699 29.358 43.967 63.364 88.459 2.041 3.688 6.248 10.020 15.356 22.657 32.373 45.007 61.115 0.778 3.084 10.991 18.316 28.768 43.101 62.143  2  Activities of each salt MgCl A1C13 NaCl 2.279 0.000 1.385 6.536 2.255 5.344 15.677 31.084 3.465 32.870 5.028 114.504 62.325 6.964 331.496 3.542 2.622 1.686 6.536 2.255 5.344 11.392 2.932 10.249 18.905 3.724 18.630 30.081 4.636 32.318 5.283 0.000 4.247 6.536 2.255 5.344 8.041 4.887 6.705 9.836 7.918 8.382 11.966 11.370 10.436 . 0.000 1.588 2.397 6.536 2.255 5.344 24.546 3.101 11.145 65.440 4.146 21.884 147.862 5.411 40.751 . 4.536 1.850 3.578 6.536 2.255 5.344 9.335 2.733 7.931 13.209 3.292 11.679 18.519 3.944 17.057 0.000 0.947 0.000 1.371 1.480 0.937 6.536 2.255 5.344 20.858 3.279 19.830 53.929 4.571 58.517 121.358 6.152 148.203 246.853 8.042 335.497 464.627 10.261 696.282 822.103 12.829 1347.860 0.000 1.145 1.099 1.702 1.636 2.507 6.536 2.255 5.344 17.736 3.016 10.688 40.614 3.929 20.191 83.365 5.008 36.290 158.037 6.264 62.446 281.669 7.707 103.436 477.611 9.348 165.692 0.000 0.000 0.000 2.809 0.000 2.057 28.057 0.000 27.529 67.685 0.000 75.181 145.717 0.000 181.149 287.437 0.000 396.082 528.968 0.000 801.306 2  CaCl  2  1.787 4.615 10.205 20.038 35.961 0.000 4.615 15.125 35.620 71.876 3.863 4.615 5.487 6.495 7.653 2.473 4.615 8.147 13.700 22.081 3.317 4.615 6.370 8.722 11.844 0.877 2.109 4.615 9.137 16.670 28.464 46.048 71.253 106.227 0.000 1.287 4.615 11.774 25.508 49.798 90.187 154.139 251.439 0.000 0.000 0.000 0.000 0.000 0.000 0.000  133  Figure A2.1  The effects o f added salts on the calculated activity coefficients  a) The effect o f H C l  b) The effect o f A1C1 & C a C l 3  c) The effects M g C l & C a C l ( l m ) 2  0  2  -•-HCl -0-A1C13  d) The effects M g C l & C a C l  2  1 2 3 Molality of M g C l & C a C l -CJ-MgC12 -A-CaC12  2  0 2  —O-NaCl 1 total  2  1 2 3 Molality of M g C l & A1CI 2  -•-HCl - O — A1C13  -0-MgC12 -A-CaC12  2  (Gm)  4 3  —O-NaCl 1 total  134  Appendix 3  A3.1  Experimental aspects: Procedures and methods  Determining activity coefficients o f H C l in the mixture o f H C l by measuring E M F o f the  cell [43, 49]  Reagents: Hydrochloric acid o f reagent grade and M g C l ( A C S certified reagent grade) 2  Stock solutions o f each electrolyte are prepared and their molalities are determined by potentiometric titration for H C l and E D T A titration for M g C l . 2  Equipment: Denver Instrument 250 (Reasearch grade p H meter pH-ISE-conductivity) Electrodes: The procedures for preparation o f hydrogen electrodes and A g / A g C l electrodes are summarized in attachments A 3 . 2 - A 3 . 3 . Measurement: Dissolved air was removed from the solution by bubbling hydrogen gas through it before the cell was filled. The cell was immersed i n a constant temperature water bath regulated to 0.1 °C with the aid o f Digi-Sense ThermoLogR R T D thermometer. The electrodes were immersed and the hydrogen gas wass bubbled through the Pt bases o f the Pt/H2 electrode. When the reading stabilized, the measurement was taken. The E M F measurement corresponded to a cell o f the type ( A ) : Pt, H (g, lat) | H C l (m ), M g C l (m ), i n H 0 | A g C l , A g ( A ) 2  A  2  B  2  A l l the E M F readings were corrected to a hydrogen partial pressure o f l a t m (use Table 9-1. Bates) Defining m  A  for the molality o f H C l , and me for the molality o f M g C l , the corresponding ionic 2  strength contribution was calculated as: y = 3m /(m + 3m ) B  B  A  B  y = m / ( m + 3m ) A  A  A  B  The E M F o f cell ( A ) is given by: E=E° -0.0591 m ( m + 2 m ) y A  A  B  2 A  From this the y or the activity coefficient o f the hydrochloric acid i n this mixture is calculated. A  Table A3.1 provides the standard potential o f the A g / A g C l reference electrode. Table A 3 . 1 . Standard potentials E ° o f the A g - A g C l electrode at temperatures [52] t,°C  5  10  15  20  25  30  35  40  E°,V  0.234  0.231  0.229  0.226  0.222  0.219  0.216  0.212  t, °C  45  50  55  60  70  80  90  95  E°,V  0.208  0.204  0.201  0.196  0.188  0.179  0.170  0.165  135  A3.2  A g - A g C l Electrode preparation Overview The silver-silver chloride electrode is a highly reproducible and reliable electrode, and it is  certainly a convenient electrode to construct and use. More notably the thermal electrolytic type is commonly used and the base o f this electrode is prepared by following manner. Materials & reagents: Helix o f #26 Pt wire, (L=7 m m , <|>=2), flint glass tube, HNO3, H C l , A g N O - 4 0 0 g , N a O H - 1 OOg, 3  Equipment, instrument, and glassware: crucible furnace, small electrolysis cell with low voltage supplier, and common lab glassware Procedures: The base for this electrode was prepared as follows. A helix o f #26 Pt wire about 7 m m in length and 2 m m in diameter was sealed in a tube o f flint glass. The bases were cleaned i n warm 6 M nitric acid and a thick paste o f well washed silver oxide and water was applied to each helix. The electrodes were suspended in a crucible furnace heated to about 500°C and allowed to remain there about 10 minutes or until they were completely white. A second layer o f silver was formed i n a similar manner with a slightly thinner paste to make the surface smooth. The silver on each electrode weighted about 150-200 mg. Each silver electrode was mounted i n a cell o f modified U-tube design and electrolyzed i n a 1 M solution o f twice-distilled hydrochloric acid for 45 minutes at a current o f 10mA. Silver was the positive electrode, and the platinum wire served as the negative electrode. If the current efficiency was 100%, 15-20 percent o f the silver would be converted to silver chloride. Thick coats o f silver chloride tend to make the electrodes sluggish and should be avoided. The completed electrodes were placed in a 0.05M solution o f hydrochloric acid overnight. The potentials o f each electrodes were then inter-compared. Individual electrodes that differ from the average o f the group by more that 0.1 m v were rejected. The purity o f hydrochloric acid and the washing o f the silver oxide are important criteria for fabricating the best electrodes. The best silver and silver chloride electrodes are light gray to white.  Preparation o f silver oxide Dissolve 338 g (2 moles) o f silver nitrate i n 3 liter o f water. Dissolve slightly less that two moles (80g) o f sodium hydroxide i n 400 m l o f water, and add the solution drop by drop to the vigorously stirred solution o f silver nitrate. Silver should be present in slight excess at the end o f the precipitation. The product should be washed thirty to forty times with distilled water.  136  A3.3 Hydrogen electrode preparation Overview: The hydrogen electrode is the primary reference electrode used to define an internationally accepted scale o f standard potentials i n aqueous solutions. This electrode commonly consists o f a platinum foil, the surface o f which is able to catalyze the reaction: H  +  + e O »/ H 2  2  The base o f this electrode is prepared as follows. Materials & reagents: Sheet o f Pt about 0.125 m m thick, Helix o f #26 Pt wire, (L=2 m m , <)>=2), asbestos board, flint glass, flint glass tubing o f 5 m m outside diameter, H C l , HNO3, lead acetate trihydrate, scrap platinum Equipment, instrument, and glassware: small gas-oxygen flame, Bunsen flame, and steam bath Procedure: Sheet o f platinum about 0.125 m m thick was cut into pieces o f about one c m . A 2  piece o f Pt wire 2 cm i n length was spot welded to the foil near the center o f one edge. The welding was accomplished by placing the foil, with the wire i n place, on a piece o f asbestos board and heating the spot to be welded with a small gas-oxygen flame. A sharp blow with a hammer joined the two pieces o f white-hot metal. The flint glass was melted over the wire and the edge o f the foil to form a bead about four m m i n diameter. This bead was then sealed into the end o f an 8 cm length of flint glass tubing o f 5 m m outside diameter. New electrodes were cleaned before use by brief immersion i n a cleaning mixture prepared by combining three volumes o f 1 2 M H C l with one volume o f 1 6 M HNO3 and four volumes o f water. For best results, the base metal surface has to be smooth. For this reason, the foil is sometimes polished with emery. Platinization is the best means o f activating the surface o f the electrode. The platinum black is best deposited from a 1 to 3 per cent solution o f chloroplatinic acid ( H P t C l ) containing a little lead acetate (0.005% lead acetate trihydrate). A current o f 200 to 400 2  6  m A was passed for 1-3 minutes i n such a direction that the electrode to be coated is negative. A similar platinum foil served as the positive electrode, (j = 10-20 m A / c m i n 2% chloroplatinic acid 2  and 2 M H C l ) The finished electrodes should be stored i n water. D r y electrodes exposed to air lose catalytic activity, and must be replatinized before use. Preparation o f Pt solution: Scrap platinum o f about 1.5 g is cleaned i n hot concentrated nitric acid, rinsed with water, and ignited to red heat i n a Bunsen flame. The metal is cut into small fragments to facilitate solution and is digested in warm aqua regia (3 volume o f concentrated H C l +  137  1 volume o f concentrated HNO3) until completely dissolved. The acid platinum mixture is evaporated to dryness on a steam bath and the residue taken up i n about 20 m l o f concentrated hydrochloric acid. The evaporation and addition o f hydrochloric acid are repeated twice. The final (fourth) evaporation should be stopped before the crystals are completely dry. The residue o f chloroplatinic acid hexahydrate, H2PtCl6*6H20, remaining after the final evaporation is dissolved i n 100 m l o f distilled water, and 80 m g o f lead acetate trihydrate is added, preferably.  A3.4  Determination o f magnesium ion in aqueous solution Mg  2 +  can be directly titrated by standard solution o f E D T A .  Pipette 2 5 m L Magnesium ion solution (c.a. 0.01M) into a 250 m l conical flask and dilute to about 100 m l with de-ionized water. Adjust the p H o f the solution to 10 by addition o f 10ml 1 M aqueous NH4CI solution, and then concentrated N H 4 O H solution drop wise until the p H about 10. A d d solochrome black and titrate with standard (0.01M) E D T A solution until the color changes from Red to Blue. Prepare a 1 M solution o f ammonium chloride by dissolving 26.75g o f the analytical grade solid in de-ionized water making up to 500ml i n a graduated flask. Use concentrated ammonia solution. Preparing indicator solution: 0.2 g dyestaff i n 15 m l triethanolamine, plus 5 m l absolute ethanol.  138  A3.5a Electrode design: Base for A g / A g C l electrode  I iL  copper wire  /flint glass tube  s -1  \ *  1  Pt wire  A3.5b Electrode design: Base for Pt/Eb electrode  copper wire to potentiometer  flint glass tube  flint glass bead about 4 mm in diameter Pt wire, L=20mm  Pt foil (10*10,1.25 mm thick)  A3.5c Electrode design: Actual design o f Hildebrand bell-type Pt/H2 electrode  flint glass tube  copper wire to potentiometer  1 H  gas  outside glass compartment  o o  flint glass bead about 4 mm in diameter  © ©  Pt foil (10*10,1.25 mm thick)  2* - 6 holes in diameter 2 mm  £ 2  A.3.6 Example o f acid determination by potentiometric titration  Table A 3 . 6 Measurements and derivatives E  AE/AV  ml  mV  mV mL"  4.6  198.6  4.65  194.6  Sol. Added  A E/AV 2  1  Figure A3.6.1 Potential vs. Solution added  2  mV mL"  Acid determination 250  2  -80  150 100  -92 4.7  190  -440 -114  4.75  184.3  -640  ^  50  S  .177167.1  b  46  4/  150.6  4.95  104.3  49  b1  b2  b  -150  -2640  -200  -330 4.9  48  -100  -1040 -198  4.85  0  -50'  -146 4.8  ._ J  200  Solution added, ml  -11920 -926 -11960 -1524  5  28.1  5.05  -127.4  Figure A3.6.2 Second derivatives vs. Solution volume  -31720 -3110 52320  Acid determination  -494 5.1  -152.1  5.15  -166.2  4240  60000  1000  40000  -232 5.2  -177.8  \  50000  -282  4640  j  30000  |  20000  jl > <  10000  HI  ^  \  \  \  \  0 . -10000 6  47  4  9  -20000 -30000 -40000  |  51  \  •  52  5  •  Solution volume, ml  142  A 3 . 7 Water vapor pressure values for the barometric pressure correction [54] t, oc  Vapor pressure  0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100  mm. H g at 0° 4,6 6,5 9,2 12,8 17,5 23,8 31,8 42,2 55,3 71,9 92,5 118,1 149,4 189,1 233,7 289,1 355,2 433,6 525,9 634 760  Appendix 4  Mass balances of selected tests  Testcond:  M A S S B A L A N C E FOR TEST ID: jc5-7.2-4100  mHCl  7.00  (chalcopyrite mineral)  1  A S SAY, (% for solids, g/1 for solutions) HCl CI (exc HCl) TOTAL S(tot) INPUT S(tot) | Co Cu Fe Mg Ni sol+tra H20 100.00 1.56 Solid Cone. 31.20 I 0.00 35.30 33.75 10.00 10.00 1-0.25 Solution 11.65 100.00 0.00 0.00 4.00 0.00 0.00 68.76 15.59  Co 0.00  Cu 1.77 0.00  Fe 1.69 0.00  I  Mg 0.00 24.22 1.69 24.22  mCuCB  2.40  0.00  0.00  t,hr  T,°C  1.00  100  M A S S , grams N i .sol+tra H20 1 HClCl-Cexc HCt) TOTAL 0.00 -0.01 5.00 416.81 94.53 70.63 606.20 70.63 611.20 0.00 I -0.01 416.81 94.53  TotlNl  1.56  0.00  1.77  100.00  1.18 0.00 0.00 1.18  0.00 0.00 0.00 0.00  1.163 0391 0.020 1.57  1.08 038 0.02 1.49  0.00 22.60 1.05 23.65  0.00 0.00 0.00 0.00  -0.07 0.00 0.00 0.00 381.81 75.41 0.00 4.84 0.00 -0.07 381.81 80.25  0.00 70.63 0.00 70.63  336 55133 5.93 560.52  mass.g -0.38 % -24%  0.00  -0.19 -11%  -0.20 -12%  -0.57 -2%  0.00  -0.05 -35.00 -14.29 430% -8% -15%  0.00 0%  -50.67 -8%  Co  DISTRrBUTTON Cu Fe Mg 1.00 1.00 0.00 1.00 0.00 0.00  Ni  OUTPUT Solid Res. LeachSol WashSol  3534  0.00 0.00 0.00  34.60 32.09 0.01 0.84 48.61 0.05 0.05 2.33  0.03 0.00 0.00  -197 0.00 0.00  162.17 10.75  32.84 0.00 OUT  |  \ S olution V olume, ml Feed Leach Wash 500.00 465.00 450.00  Accountability  |  i  !  RECOVERY,%  Test cond:  (Low M gO c one entrate)  INPUT S(tot) Solid Cone. 2952 Solution  OUTPUT Solid Res. Leach.Sol Wash.Sol  2650  Co 0.28  0.38 0.08 0.01  1 1 1 ASSAY, (°/b for solids, g/1 for solutions) Fe Mg Ni sol+tra H20 HCl CHexc HCl) TOTAL S(tot) Cu 100.00 7.48 032 38.49 4.55 1350 12.94 0.00 0.00 4.03 0.00 0.00 70.71 13.49 11.76 100.00 TotIN 7.48  0.22 0.08 0.01  25.22 4.94 16.08 52.09 0.90 l~2.86  Solution Volume, ml Feed Leach Wash 500.00 474.00 390.00  11.61 31.13 4.86 0.00 0 3 f 1 0.00  12792 9.09  33.48 0.00  Accountability: I RECOVERY,%  Co 0.07  mHCl mMgCU mcuCU rtiFeCB  t,nr  T,°C  6.00  1.00  100  Mg 1.14 24.22 25.36  240  0.00  0.00  MASS,grams Ni isol+tra H20 H a Cl-(exc HCl) TOTAL Co 337 3.24 25.00 1.00 424.60 81.03 70.63 600.48 0.00 337 3.24 424.60 81.03 70.63 625.48  0.07  Cu | Fe 0.08 9.62 0.00 0.00 0.08 9.62  100.00 2.28 0.00 0.00 OUT 2.28  0.03 0.04 0.00 0.07  0.019 2.17 0.43 0.037 7.62 24.69 1.12 0.002 035 0.06 10.15 26.23  1.00 2.30 0.12 3.43  2.68 0.00 0.00 2.68  mass,g -5.20 % -69% i  0.00 2%  -0.02 -27%  0.05 1%  -0.55 -26.00 -16.85 -17% -6% -21%  Solid based: Sol. Based:  0.73 036 0.02  0.00 0.96 0.04  34.13 36.10 23.34 24.15 97.65  Solid based: S o l Based:  M A S S B A L A N C E FOR TEST ID: 1B5-6.2-4-100  0.74 0.25 0.01  053 5%  0.88 3%  | 52.86 76J00 7741 62.56 7034 55.25 49.02 82.87 102 71.84  0D0 398.60 0.00 398 60  0.00 60.63 354 64.18  0.00 70.63 0.00 70.63  8.62 564.56 5.14 578.32  0.00 0%  -47.17 -8%  0.46 0.51 0.03  DISTRIBUTION Cu Fe Mg 0.04 1.00 1.00 0.00 0.00 0.96  Ni 1.00 0.00  0.33 0.63 0.04  0.29 0.67 0.04  0.21 0.75 0.03  0.02 0.94 0.04  MASS BALANCE FOR TEST ID: 1B5-8.2-2 1 (Low MgO concentrate) | 1 I | S(tot) INPUT Solid Cone. 2952 Solution  OUTPUT Solid Res. Leach.Sol WashSol  2538  Co 0.28  Cu 032 0.00  0.24 0.11 0.01  0.28 0.08 0.01  Test cond:  8.00  ASSAY, (% for solids, g/1 for solutions) Fe Mg Ni isol+tra H20 HCl Cl-Cexc HCl) TOTAL SCtot) 38.49 455 13.50 1 12.94 ! 100.00 7.48 0.00 3.96 0.00 I 0.00 66.84 17.66 11.54 100.00 |TotIN 7.48  22.29 653 17.81 51.40 1.15 3.11  4.12 6.82 0.43  40.76 0.00 0.00  156.65 11.25  100.00  1.62 0.00 0.00  OUT  1.62  33.20 0.00  Co 0.07  Cu 0.08 0.00 0.07 1 0.08  I  M A S S BALANCE FOR TEST ID: 3B5-6.2-1-100 (high MgO concentrate)  OUTPUT Solid Res. Leach Sol Wash.Sol  12.68  Co 0.68  0.49 0.27 0.02  0.018 1.43 0.44 0.038 837 24.16 0.003 0.46 1.24 0.07 0.06 1025 | 25.85  T,°C  t,hr 0.00 2.00  100  2.61 0.00 0.00 0.00 379.02 73.63 0.00 0.00 4.50 2.61 379.02 78.13 \  0.00 70.63 0.00 70.63  6.40 0.22 559.10 0.73 638 0.04 571.88  0.00 0%  -o"5.03 -10%  DISTRIBUTION Cu Fe Mg 1.00 1.00 0.04 0.00 0.00 0.96  Ni 1.00 0.00  0.14 0.82 0.04  0.02 0.93 0.05  0.07 0.88 0.05  DISTRIBUTION Fe Mg Cu 1.00 1.00 0.09 0.00 0.00 0.91  Ni 1.00 0.00  0.11 0.85 0.04  0.08 0.90 0.02  031 0.64 0.05  |  "ma mntgCE mcucu mjFeCB t,hr 6.00 2.40 0.00 0.00 1.00  T,°C 100  1  10.77 6.14 10.28 59.63 I 932 56.99 12.76 0.00 | 0.54 2.89 0.42 0.00 i  Solution Volume, ml Feed Leach Wash 500.00 475.00 340.00  026 321 0.17 3.64  j  Test cond:  ASSAY, (<H> for solids, g/1 for solutions) Cu Fe Mg Ni Insl+tr H20 HCl Cl-Cexc HCl) TOTAL S(tot) 0.12 21.19 9.33 25.75 22.70 100.00 5.06 0.00 0.00 4.03 0.00 0.00 70.71 13.49 11.76 100.00 ToUN 5.06  0.01 0.01 0.00  0.00  mass.g -5.86 0.00 -0.02 0.63 0.49 027 -0.63 -30.00 -2951 Accountability: 2% 8% -19% -7% -28% % -78% 0% -27% 7% 1 Solid based: 7754 77153 85.18 61 DO 92.19 RECOVERY,% 77.56 5053 91.73 100.19 100.11 Sol. Based:  Solution Volume, ml I Feed Leach Wash 500.00 470.00 400.00  INPUT S(tot) Solid Cone 20.23 Solution  2.40  MASS, grams HCl Cl-(exc HCl) TOTAL Co Fe I Mg Ni sol-Kta H20 9.62 | 1.14 337 3.24 25.00 1.00 409.02 108.04 70.63 61151 0.00 0.00 I 24.22 9.62 ! 25.36 337 3.24 409.02 108.04 70.63 63651  0.02 0.05 0.00 1  T  K>HC1 ttlMgCBmcucc  117.51 9.38  33.55 0.00  Accountability:  Cu | 0.03 | 0.00 0.17 1 0.03  Fe 5.30 0.00 5.30  Mg 233 24.22 26.55  MASS,grams Ni InsWr H20 HCl Cl<exc HCl) TOTAL Co 6.44 5.67 : 25.00 1.00 1424.60 81.03 70.63 600.48 0.00 6.44 5.67 424.60 81.03 70.63 625.48  100.00 0.67 0.00 0.00 OUT 0.67  0.03 0.13 0.01 0.16  0.001 0.005  0.57 4.43  0.33 27.07 0.000 I 0.18 0.98 0.01 i 5.18 28.38  0.54 6.06 0.146.75  3.16 0.00 .0.00 3.16  mass.g -4.39 % -87%  -0.01 -7%  -0.02 -81%  -0.12 -2%  0.31 5%  -251 -25.00 -22.02 -44% -6% -27%  Solid based:  84J61 98J08 8922 86.04 9154 77.83 17.16 87.02 105.65 96.33  1 RECOVERY,%  Co 0.17  Sol. Based:  1.83 7%  1 0.00 399.60 ) 0.00 399.60  0.00 55.82 3.19 59.01  0.00 70.63 0.00 70.63  5.30 0.17 563.74 0.80 4.51 0.03 57355  0.00 0%  -51.94 -8%  0.10 0.85 0.05  0.01 0.95 0.03  Test cond:  MASS B A L A N C E FOR TEST ID: 3B5-6.2-HTI) (High MgO concentrate)  mHCl  6.00  2.00  mcucn 0.00  t,hr  T,°C  0.00 1.00  100  1 1  INPUT S(tot) Solid Cone. 20.23 Solution  OUTPUT Solid Res. Leach.Sol Wash.Sol  14.78  Co 0.68  054 0.26 0.02  Cu 0.12 0.00  0.02 0.01 0.00  ASSAY, (% for solids, g/1 for solutions) HCl Cl-(exc HCl) TOTAL S(tot) Co Fe Mg Ni sol+tra H20 100.0 5.06 0.17 21.19 9.33 23.73 22.70 100.0 0.00 4.03 0.00 0.00 70.71 13.49 11.76 Totrw 5.06 I 0.17  12.44 6.10 11.52 34.60 8.87 48.84 11.65 0.00 0.57 3.21 0.78 0.00  Solution Volurae, ml Feed Leach Wash 300.00 483.00 360.00  Accountability:  1 RECOVERY,%  0.80 .0.39 438 2359 0.21 1.15 1 5.2825.14  0.74 5.63 0.28 6.64  3.49 0.00 0.00 3.49  -1.41 -5%  0.21 3%  -2.18 -17.00 -13.76 -38% -4% -17%  0.001 0.005 0.000 0.01  mass.g -4.11 % -81%  0.00 -3%  -0.02 -78%  Solid based: Sol Based:  -0.01 0%  0.00 0.00 407.6 64.17 0.0 3.10 407.6 6737  0.00 7063 0.00 70.63  640 576.0 4.74 5873  0.00 0%  -38.30 -6%  0.21 0.73 0.04  DISTRIBUTION Cu Fe Mg 1.00 0.09 1.00 0.00 0.00 091  Ni 1.00 0.00  0.17 0.77 0.06  0.02 0.94 0.05  0.11 0.85 0.04  DISTRIBUTION Fe Mg Cu 1.00 0.09 0.02 098 0.00 091  Ni 1.00 0.00  0.02 0.92 0.06  0.82 0.17 0.01  0.15 0.81 0.04  I 7968 9631 8458 8326 8854 7694 18.08 84.72 93.20 91.75  Test cond:  MASS B A L A N C E FOR TEST ID: 3B5-6.2-0.05CuC12 (High MgO concentrate)  MASS, grams Ni [sol+tra H20 HCl Cl<excHCt) TOTAL Co 6.44 5.67 25.00 1.00 424.6 81.03 7063 6005 0.00 6255 6.44 5.67 424.6 81.03 70.63  I  0.03 0.12 0.01 0.17  OUT  Mg 2.33 24.22 5 30 26.55  0.03  0.95 0.00 0.00 095  100.0 34.12 0.00  1329 8.60  Cu | Fe 0.03 5.30 0.00 0.00  mHCl mMgCB mcucn  2.00  6.00  0.05  t,hr 0.00 1.00  T,°C 100  1 1  INPUT S(tot) Solid Cone 20.23 Solution  OUTPUT Solid Res. LeachSol WashSol  27.97  Co 0.68  0.88 0.03 0.00  Cu 0.12 0.29  0.17 330 032  ASSAY, (% for solids, g/1 for solutions) Fe Mg Ni sol+tra H20 H a Cl-(exc HCl) TOTAL S(tot) 100.0 5.06 21.19 933 25.75 22.70 12.01 100.0 0.00 4.01 0.00 0.00 70.28 1341 TotlN 5.06  19.18 2.47 32.05 1738 4.18 48.14 2.21 0.00 0.39 4.62 0.22 0.00  0.17  Cu 0.03 1.74 1.78  Fe 530 0.00 530  Mg 233 24.22 26.55  4.71 0.00 0.00 4.71  0.15 0.01 0.00 0.16  0.029 1.64 0.11 1.77 !  3.23 2.07 0.13 5.43  0.42 23.83 157 25.81  mass.g -0.35 Accountability: % -7%  -0.01 -5%  0.00 0%  0.13 2%  -0.74 -3%  100.0 121.4 1393  35.93 0.00 OUT  Co 0.17  MASS,grams Ni sol+tra H20 H a Cl<exc HCl) TOTAL Co 6.44 5.67 25.00 1.00 7258 6043 0.00 424.6 81.03 6.44 5.67 424.6 81.03 7258 629.2  3.39 1.09 0.07 6.56  2.91 0.00 0.00  0.00 0.00 419.6 60.08 0.0 4.74 291 I 419.6 64.82  0.00 7258 0.00 72.58  16.83 5809 6.62 604.4  0.12 2%  -2.77 -49%  0.00 0%  -24.82 -4%  |  Solution Volume, ml Feed Leach Wash 500.00 495.00 340.00  1  RECOVERY,%  Solid based: Sol. Based:  1322 3J60 39J07 822 1620 8.48 983 4155 93.7 18.10  -5.00 -1631 -1% -20%  0.91 0.08 0.01  059 038 0.02  0.02 0.92 0.06  Test cond:  MASS B A L A N C E FOR TEST ID: 3B5-6.2-02CuC12 (high M gO c one entrate) !  INPUT  S(tot)  Solid Cone. 20.23 Solution  OUTPUT Solid Res.  Co 0.68  T,°C  1.00  100  2.40  I  0.80  0.20  0.09  WashSol  0.01  11.43 ! 6.09 54.26 0.94 0.42 3.69  2.64  27.98 29.36 4.97 0.00 037  134.05  0.00  Cu  Fe  Mg  0.17 0.17  0.03 5.50 5.53  5.30 0.00 5.30  2.33 24.22 26.55  soB-tra H20 : HCl Cl<exc HCl) TOTAL Co 25.00 1.00 6.44 5.67 76.77 601.05 0.00 413.54 8103" 626.05 6.44 5.67 413.54 81.03 i 76.77 |  100.00 •322  0.12  0.030  2.49  039  4.09  4.29  0.00  0.04  5.488  2.92  26.05  2.39  0.00  0.00 322  0.00 0.16  0.515 6.03  0.23 5.64  2.03 28.46  0.20 6.68  0.00 4.29  0.00 0.00 | 0.00 393.54 64.34 1 76.77 0.00 5.31 | 0.00 393.54 69.66 I 76.77  mass.g -1.84 % -36%  -0.01 -3%  0.51 9%  0.34 6%  1.91 7%  0.25 4%  -138 -24%  -20.00 -11.37 -5% -14%  Solid based: Sol. Based:  31JQ2  36.85 0.00  9.66  i S olution V olume, ml Feed Leach Wash 500.00 480.00 550.00  Accountability: 1  RECOVERY,%  (high MgO concentrate)  1  "ma mjigcu mcaCB «1F«C13 t,hr 6.00 2.40 0.00 0.20 1.00  |  Solid Cone. 20.23 Solution  OUTPUT Solid Res.  21.70  0.68  Cu  I Fe M g 1 21.19 9.33  0.12 0.00 ' 0.86  3.96  Ni  soHtra H20  1.00 0.00  0.09 0.91  1.00 0.00  0.71  0.00  0.44  0.01  0.61  571.53 0.26  0.91 0.09  0.52 0.04  0.92 0 07  0.36  14.63 8.30  0.02  003  59446 -3159 -5%  T,°C  |  100  MASS, grams  25.75 22.70 0.00 0.00  0.89  0.01 1 18.11 2.42  29.86 27.01  0.06  4.52  0.00  WashSol  0.01  0.02 1 18.00 55.19 0.00 ! 1.47 4.14  0.40  0.00  68.79  Cu HCl iCHexc HO) TOTAL S(tot) Co 100.00 5.06 0.17 0.03 13.17 100.00 0.00 13.23 TotM 5.06 ! 0.17 0.03  Fe  Mg  Ni  sol+tra H20  5.30 233 5.24 24.22 10.54 26.55  6.44 6.44  5.67  Ha  Cl<exc HCT) TOTAL  5.67 421.20 81.03 421.20 81.03  80.62 80.62  Co  DISTRIBUTION Cu | Fe Mg  25.00 612.31 637.31  1.00 0.00  1.00 0.00  I i  0.50 0.09 050 0.91  Ni 1.00 0.00  3.19  0.13  0.002  2.66  0.36  4.39  3.97  0.00  0.00  14.71  0.80  0.15  0.22  0.01  0.65  38.29  0.00  0.03  0.008  8.55  26.21  2.15  0.00  396.20 65.62  80.62  579.39  0.19  0.75  0.72  0.92  0.32  0.00  0.00 3.19  0.00 0.16  0.001 0.01  0.63 1.78 11.85 28.35  0.17 6.71  0.00 3.97  0.00 5.42 396.20: 71.04  0.00 80.62  8.01 1602.11  0.02  0.10  0.05  0.06  0.03  -0.01 -4%  -0.02 -66%  1.31 12%  0.27 4%  0.00 0%  -35.20 -6%  100.00 0.00 12.62  | OUT  1 mass,g -1.87 Accountability: % -37% RECOVERY,%  4^ -J  Ni  0.01 0.99  I  LeachSol  Solution Volume, ml Feed Leach Wash 500.00 475.00 430.00  000 0%  DISTRIBUTION Fe Mg  Cu  1  ASSAY,(% for solids, g/1 for solutions) Co  Ni  i 2J6 53.00 8 3 4 7 3 6 4 1 27.61 108.64 59.46 105.75 40.22  Test cond:  MASS B A L A N C E FOR TEST ID: 3B5-6.2-02FeCB  S(tot)  0.00  Co  OUT  INPUT  0.00  MASS, grams  ASSAY, (% for solids, g/1 for solutions) Ni isoHtia H20 ! HCl Cl-(exc HCl) TOTAL S(tot) 100.00 5.06 25.75 22.70 12.77 100.00 0.00 0.00 68.80 13.48 TotM 5.06  Mg Cu Fe 0.12 1 21.19 9.33 0.91 | 0.00 4.03  17.02  t,hr  6.00  |  Lea.ch.Sol  22.00  K>HC1 raKjCQ mcaCU my,cB  Solid based: Sol. Based:  0.00  |  180 7%  i  23.14 94.81 49.71 84.73 31.78  19.55 28.72 87.13 105.44 35.98  -1.70 -25.00 -9.99 -30% -6% -12%  

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