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Evaluation of NP determination by static tests for ARD prediction Wang, Ying 1998

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E V A L U A T I O N O F NP D E T E R M I N A T I O N B Y STATIC TESTS F O R A R D PREDICTION by YING WANG B.Sc, Heilongjiang Inst, of Mining and Tech., 1982 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF APPLIED SCIENCE in THE FACULTY OF GRADUATE STUDIES (Department of Mining and Mineral Process Engineering) We accept this thesis as conforming to ttu^required standard THE UNIVERSITY OF BRITISH COLUMBIA January, 1998 ©Ying Wang, 1998 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department of M i A i y J ^ - (_ CJL**T <^^Y The University of British Columbia Vancouver, Canada Date R b . DE-6 (2/88) ABSTRACT In the prediction of acid rock drainage (ARD), static tests play a very important role. The objective of static prediction tests is to determine the balance between the acid producing potential (AP) and the acid neutralization potential (NP) of waste material. The results of static tests are used as initial screening data to characterize waste materials either as "safe" or "unsafe" for disposal. The classification of the waste can be based on either the difference between NP and AP, termed the Net Neutralization Potential (NNP) or the ratio between NP and AP, termed NPR. Errors in measuring either of AP or NP can result in a mis-classification of a material type. In the natural environment, ARD will only occur if there is not sufficient neutralizing alkalinity. Such alkalinity can be provided by many common rockforming minerals. These minerals can neutralize acid in different pH ranges. More importantly, different minerals have different values of reactivity. For low reactivity minerals, their presence in a waste will not necessarily provide protection against ARD if the rate of neutralization is less than the rate of acid generation. Carbonate minerals, especially calcite and dolomite, are the most effective neutralizing minerals because they have relatively high reactivity and neutralize acid in the circum-neutral pH range. Silicate minerals can also be important neutralizers because of their abundance but their reactivities relative to the carbonates range from intermediate (for example, the calcium-rich feldspars) to extremely slow (for example, K-feldspar). This limits the contribution of silicate minerals to the effective field-NP. This thesis focuses on the problems that can arise in the determination of neutralization potential, NP, and in the interpretation of NP data from static methods. In this study the neutralization potentials of 119 samples were determined by three commonly used static tests (the Sobek ABA and variations, the Modified ABA and carbonate NP). Some selected samples were tested using the method proposed by Lapakko in 1994. Several conclusions and recommendations were made from this study as follows: 1. NP values depend on sample mineralogy and test conditions. The NP value of a sample using the Sobek ABA test, the Modified ABA test, C0 2 analysis and the Lapakko method were found to have a wide variation. 2. In most cases, the Sobek method gives the highest NP value due to its vigorous test conditions. The increased acidity in the Sobek digestion procedure resulted in an increased dissolution of silicate minerals as evidenced by a corresponding increase in silicate mineral cation concentrations. The Sobek method can, therefore, be expected to overestimate the effective field-NP value for many samples. 3. Compared to the Sobek ABA, the Modified ABA is considered to provide more practical NP values by accounting for only most reactive silicate minerals in addition to iii the carbonate minerals. For the same reason, therefore, the modified ABA NP values are often higher than the Carbonate NP values. 4. The Lapakko method attempts to measure the NP value that is available to neutralize acid before the onset of ARD or in the early stages of acid generation within wastes. It is a useful tool for research, but it is not suitable for the use as a routine procedure in industry and commercial labs since it is very time consuming procedure. 5. In the Sobek ABA method, the fizz test is very important but a subjective measurement. It is used to determine the acid quantity added during the digestion stage, which in turn is critical for the NP value obtained. Misinterpretation or misuse of the fizz test can lead to significant variations in the NP values obtained by the procedure. Generally, when the fizz rating is increased, the NP value of a sample is increased correspondingly. 6. Back titration curves can be obtained for the titration stage in Sobek test. The shape of the curve can indicate if significant silicate mineral dissolution has occurred in the test. The use of such curves might be a helpful supplement in the interpretation of Sobek test results. 7. For the reference standard material NBM-1, the impact of test method on NP and NP:AP ratio was found to be particularly significant. NP:AP ratios of 1.7 to 10.2 were obtained for the same material. iv 8. Prediction of ARD potential, including the practical NP of a waste, may be obtained by a variety of methods, including detailed mineralogical characterization, comparisons with other sites, drainage monitoring, static laboratory tests, kinetic laboratory test and on-site field trials. A conclusion from this thesis is that no single test alone is conclusive. To get a confident and accurate predictive result, a combination of the above methods and other analyses should be carried out. 9. In practice, only a single static test is likely to be carried out. If this is the case, the modified ABA procedure is recommended since it has the following advantages: • It is rapid and easy to perform. • It has a low cost and can be used to screen a large number of samples for possible further selective and more detailed evaluation. • No special equipment is required. • AP value calculated based on the sulfide sulfur is more realistic assessment than the AP value based on the total sulfur. • The test determines the NP contributed by the reactive silicate minerals in addition to carbonate minerals. v TABLE OF CONTENTS A B S T R A C T ii T A B L E OF CONTENTS vi LIST OF T A B L E S ix L I S T OF F I G U R E S xi A C K N O W L E D G E M E N T S xiii 1.0 INTRODUCTION 1 1.1 ACID ROCK DRAINAGE AND PREDICTION ESTING 1 1.2 RESEARCH OBJECTIVES AND SCOPE 5 2.0 L I T E R A T U R E R E V I E W 7 2.1 REVIEW OF ACID ROCK DRAINAGE 7 2.1.1 Introduction 7 2.1.2 Acid Generation 8 2.1.3 Acid Neutralization 11 2.1.4 2.1.4 Development of ARD 16 2.1.5 Implications of Neutralizing Mineral Weathering for NP Determination 19 2.3 ARD PREDICTION A N D STATIC PREDICTION TESTS 21 2.3.1 Introduction 21 2.3.2 The Standard Acid-Base Accounting (Sobek Method) 24 2.3.3 Modified Acid Base Accounting Test 32 2.3.4 The Procedure ofNP Determination Proposed by Lapakko 35 2.3.5 Interpretation of Static Test Results 38 3.0 E X P E R I M E N T A L PROCEDURES 44 3.1 SAMPLES A N D SAMPLE PREPARATION 44 vi 3.2 DETERMINATION OF ACID GENERATING POTENTIAL 45 3.3 NEUTRALIZATION POTENTIAL B Y THE SOBEK A B A METHOD 46 3.3.1 Standard Method 46 3.3.2 Use of a Different Fizz Rating in the Sobek Method 46 3.3.3 Back Titration Curves Obtained from the Sobek Tests 47 3.4 NEUTRALIZATION POTENTIAL B Y MODIFIED ACID BASE ACCOUNTING 47 3.5 NEUTRALIZATION POTENTIAL B Y CARBONATEANALYSIS 48 3.6 NEUTRALIZATION POTENTIAL B Y THE L A P A K K O METHOD 48 3.7 OTHER ANALYS E S 49 3.7.1 Mineralogical Analysis by X-Ray Diffraction 49 3.7.2 Analysis of Sobek Digestion Leachates 49 4.0 R E S U L T S A N D DISCUSSIONS 50 4.1 COMPARISON OF NP BY THE SOBEK, THE MODIFIED AND THE CARBONATE METHODS50 4.2 NP BY THE LAPAKKO METHOD 60 4.3 EVALUATION OF THE SOBEK TEST PROCEDURE ON THE MEASUREMENT OF NP 61 4.3.1 Effect of Different Fizz Rating on the Sobek NP 62 4.3.2 Effect of Different Fizz Rating on Endpoint pH of Digestion Using Sobek 73 4.3.3 Effect of Different Fizz Rating on Cation Dissolution 80 4.3.4 Effect of NP Determination method on Net NP and NP.AP Ratio 84 4.4 BACK TITRATION CURVES 91 4.5 MINERALOGICAL ANALYSIS BY XRD 95 4.6 THE TEST RESULTS FOR REFERENCE STANDARD NBM-1 97 5.0 C O N C L U S I O N S A N D R E C O M M E N D A T I O N S 100 6.0 R E F E R E N C E S 105 vii APPENDIX I THE STANDARD ACID BASE ACCOUNTING PROCEDURE OF SOBEK ET AL (1978) 1 1 5 APPENDIX II THE MODIFIED ACID BASE ACCOUNTING PROCEDURE OF LAWRENCE AND WANG (1997) • 1 1 7 APPENDIX III BACK TITRATION CURVES FOR ALL SAMPLES TESTED IN THIS STUDY 119 viii LIST OF TABLES Table 2-1. Grouping of Mineral According to Their Acid Neutralization Capacity (Kwong, 1993, after Sverdrup, 1990) 21 Table 2-2. Volume and Normality of HC1 for Use in the Sobek NP Determinations . Based on the Fizz Rating (2g Sample) 27 Table 2-3. Volume and Normality of HC1 for Use in the Modified NP Determinations Based on the Fizz Rating (2g Sample) 34 Table 2-4. Comparison of Static Test Interpretation by NNP and NP/AP ratio 49 Table 2-5. Screen Criteria Based on ABA Test Results 40 Table 4-1. Fizz Rating, The Sobek NP, Modified NP and the Carbonate NP for All Samples 53 Table 4-2. NP Values by the Sobek, Modified, Carbonate and the Lapakko Procedures- 61 Table 4-3. Fizz Ratings, AP, Sobek NPs, Net NPs and NP: AP Ratios for All Samples- 65 Table 4-4. NPs by the Sobek Procedure for No Fizz Samples 79 Table 4-5. NPs by the Sobek Procedure for Slight Fizz Samples 70 Table 4-6. NPs by the Sobek Procedure for Moderate Fizz Samples 71 Table 4-7. NPs by the Sobek Procedure for Strong Fizz Samples 72 Table 4-8. The Range of Final pH Values for the Sobek Test 73 Table 4-9. pH after Digestion by the Sobek procedure for No Fizz Samples 76 Table 4-10. pH after Digestion by the Sobek procedure for Slight Fizz Samples 77 Table 4-11. pH after Digestion by the Sobek procedure for Moderate Fizz Samples 78 Table 4-12. pH after Digestion by the Sobek procedure for Strong Fizz Samples 79 ix Table 4-13. Analysis of Digestion Leachates for the Sobek Tests 81 Table 4-14(a). Interpretation of Sobek Results for No-Fizz Samples by Net NP and NP: AP Ratio Criteria 86 Table 4-14(b). Interpretation of Sobek Results for Slight-Fizz Samples by Net NP and NP: AP Ratio Criteria 87 Table 4-14(c). Interpretation of Sobek Results for Moderate-Fizz Samples by Net NP and NP:AP Ratio Criteria 88 Table 4-14(d). Interpretation of Sobek Results for No-Fizz Samples by Net NP and NP:AP Ratio Criteria 89 Table 4-15(a). Minerals Identified by X-Ray Diffraction in selected samples (UBC) 90 Table 4-15(b). Minerals Identified by X-Ray Diffraction in selected samples (CANMET)- 90 Table 4-16. The Results for Sample NBM-1 98 X LIST OF FIGURES Figure 2-1. Relationship between pH and Concentrations of Carbonate Species (from Freeze and Cherry, 1979) 13 Figure 2-2. The Mineral Stability Series in Weathering (Sherlock et al, 1995; Godich, 1938; and Willams, 1990) 17 Figure 2-3. The Simplified ARD Development and the Reactions Flow-Path (Lawrence and Day, 1997) 18 Figure 2-4. The Relationship of NP:AP Ratio and Sulfide-S Content 41 Figure 4-1. Comparison of the Sobek NP, Modified NP, and the Carbonate NP for All Samples 56 Figure 4-2. The Correlation of the Sobek NP and the Modified NP 57 Figure 4-3. The Correlation of the Sobek NP and the Carbonate NP 58 Figure 4-4. The Correlation of the Modified NP and the Carbonate NP 59 Figure 4-5. Mineral Reactivity in ABA NP Procedures 52 Figure 4-6. NP Values Obtained by the Sobek Procedure at Different Fizz Ratings for All Samples 68 Figure 4-7. NPs by the Sobek Procedure for No Fizz Samples 69 Figure 4-8. NPs by the Sobek Procedure for Slight Fizz Samples 70 Figure 4-9. NPs by the Sobek Procedure for Moderate Fizz Samples 71 Figure 4-10. NPs by the Sobek Procedure for Strong Fizz Samples 72 Figure 4-11. pH after Digestion from the Sobek procedure 75 Figure 4-12. pH after Digestion by the Sobek procedure for No Fizz Samples 76 xi Figure 4-13. pH after Digestion by the Sobek procedure for Slight Fizz Samples 77 Figure 4-14. pH after Digestion by the Sobek procedure for Moderate Fizz Samples 78 Figure 4-15. pH after Digestion by the Sobek procedure for Strong Fizz Samples 79 Figure 4-16. Analysis of the Sobek Digestion Leachates for Testing of Sample 305-WR at Different Fizz Ratings 82 Figure 4-17. Analysis of the Sobek Digestion Leachates for Testing of Selected Sample at Different Fizz Ratings 83 Figure 4-18. Back Titration Curve for Sample 201 -WR (Standard Fizz: Moderate, the Carbonate NP=20, the Modified NP=27) 94 xii ACKNOWLEDGEMENTS First, I would like to express my deepest gratitude to my supervisor, Dr. Richard Lawrence, for his thorough and invaluable guidance and support in every aspect of my research work. The immense influence he presented in shaping my research approach and attitude can never be overestimated. I would like to give my sincere thank to Dr. George Poling for his comments and advice in my thesis work, to Dr. Dogan Paktunc for performing the XRD analyses at CANMET, and to Larry Wong of MMPE, UBC for the AA analyses. My sincere thanks are also due to Mr. Frank Schmidiger, Mrs. Sally Finora and Mrs. Marina Lee for their kind help. Finally, I must thank my husband, Yingbin He, for his support and care throughout my student years, and my sons, David He and Darrick He, who give me great joy and full-time work. xiii 1 1.0 I N T R O D U C T I O N 1.1 ACID ROCK DRAINAGE AND PREDICTION TESTING The serious environmental consequences of acid rock drainage (ARD) have become one of the most important challenges for the mining industry. ARD occurs as a result of natural oxidation of sulfide minerals contained in rock when exposed to air and water. The oxidation reactions are often accelerated by biological reactions and can yield low pH water which has the potential to mobilize any heavy metal that may be contained in the waste rock or elsewhere. Even though the pH of the resultant drainage might be close to neutral, it can contain products of the acid generation process, typically elevated metal levels and sulfate, and can cause a detrimental impact on water quality in the receiving environment. Acidic drainage and associated heavy metal contamination can be attenuated, however, due to reactions with neutralizing minerals contained in the wastes. In contact with acidic water, different neutralizing minerals can dissolve and consume acid at different rates. The rate of neutralization will reflect site-specific factors such as mineral composition, aqueous pH, temperature, and grain size. So the water quality emerging from a waste rock dump or tailings impoundment depends mainly on the balance between the acid producing oxidation reactions and the neutralizing reactions taking place within the waste material as a function of time. This balance provides the theoretical basis for ARD 2 prediction tests although in reality, the factors affecting acid generation and neutralization are much more numerous and complex. The purpose of ARD prediction testing is to provide sufficient data to satisfy the mine proponents, operators and the regulatory authorities that the potential for ARD generation can be predicted and controlled. Static prediction tests are used to provide a quick and inexpensive means of evaluating if a mine waste will produce acidic drainage. The results are commonly used as a preliminary screening of samples in the process of mine waste characterization prior to conducting more detailed evaluation by method such as kinetic tests. The acid base accounting (ABA) procedure of Sobek et al (1978) is a widely used static test method. It is approved by the British Columbia Ministry of Employment and Investment (MEI) as one of the recommended methods for the prediction of ARD in British Columbia (Price, 1997). The Sobek ABA method attempts to balance the theoretical amount of acid that can be produced (acid potential, AP) based on an assayed total sulfur value, assuming both total oxidation of pyrite and complete precipitation of iron, with an experimentally determined acid consumption value (neutralization potential, NP). In the Sobek test, the NP is determined by subjecting a finely ground sample of the material to digestion in excess hydrochloric acid under boiling conditions and measuring the quantity of acid consumed. Generally, after acid digestion, the pH of the pulp is very low which would generally not happen in the actual environmental 3 conditions. Furthermore, not all sulfur will be oxidized to produce acid, neither will all the neutralizing minerals be available for reaction as determined under the vigorous conditions of the test. Under such highly acidic and high temperature conditions, many low reactivity minerals, mainly silicates which have been classified as intermediate, slow, or very slow weathering (Sverdrup, 1990; and Kwong, 1993) will react in the digestion stage and contribute to the apparent NP of a sample in addition to the more reactive carbonate minerals (Lawrence and Wang, 1997). Such extreme conditions do not generally occur in the conditions found in the mining wastes. Although the dissolution of some silicates might occur under lower pH conditions which can develop in wastes, the rate and degree of dissolution and /or alteration will be much lower, perhaps by several orders of magnitude, than in the Sobek test (Lawrence and Wang, 1997). Morin (1990) has pointed out that samples predicted to generate net acidity by ABA have not done so and samples predicted to remain pH-neutral have eventually generated net acidity. Lawrence (1990) indicated that the Sobek ABA method could give a overestimation of the neutralization capacity of some waste materials due to the boiling test conditions. Lapakko (1994) examined ten metal mine wastes and concluded that the standard ABA and the modified ABA tended to overestimate the neutralization potential present as calcium carbonate and magnesium carbonate with the extent of overestimation depending on the minerals in the wastes. Brown and others (1995) suggested that when siderite is present, the Sobek NP procedure does not allow sufficient time for ferrous iron oxidation and ferric hydroxide precipitation, and therefore erroneously high NP values 4 can be generated providing inaccurate NP information. Li (1997) noted that static acid mine drainage prediction test procedures report the NP of a rock sample as a bulk value without regard for mineralogical composition and dissolution rates, so that the non-judicious use of this NP can result in false ARD predictions. Other works related to Acid Base Accounting testing are discussed in Chapter 2. Although all static test procedures attempt to provide an assessment of both AP and NP of a mine waste sample, it is the latter determination which is considered to be the most critical. Determination of the NP which will be available under actual environmental conditions is an essential part of waste characterization in the development of confident waste management plans to prevent or control the generation of acidic rock drainage from waste dumps, tailings impoundments and other mine components during mining operations and after mine closure. It has been stated that the largest discrepancies arise in static test is the assessment of NP (Lawrence, 1997). The NP determined by routine laboratory analysis can be uncertain depending on sample mineralogy and the conditions of the method used. To achieve more accurate acid rock drainage (ARD) prediction and confident waste management planning and permitting of mines, the design of prediction testing conditions and procedures and the interpretation of test results become extremely important. The work reported in the thesis is based on the evaluation of the neutralization potential (NP) for 119 mine waste samples from 12 different mine sites as part of prediction testing 5 for acid rock drainage. Specifically, results of the Sobek method under standard and altered conditions have been assessed and compared with those by other static test procedures (the Modified ABA, the Carbonate NP and Lapakko NP). In Chapter 2, the basic concepts related to acid rock drainage and ARD prediction are reviewed. Special emphasis is placed on the acid neutralization potential and the static test procedures for NP determination. In Chapter 3, the various static test procedures, analytical techniques and other experimental procedures are described. The tests evaluated were the Sobek ABA method (1978), variations of the Sobek method based on different fizz ratings, the Modified ABA procedure of Lawrence (1990) and Lawrence and Wang (1997), a method of determining NP based on C0 2 analysis (Carbonate NP) and a method proposed by Lapakko (1994). In Chapter 4, the results of NP determinations for 119 samples using the above procedures are presented and discussed. In Chapter 5, conclusions and recommendations for ARD static prediction tests, and how to get more accurate prediction results, especially for the data analysis and interpretation, are presented. 1.2 RESEARCH OBJECTIVES AND SCOPE The objectives of this study were as follows: 6 • to evaluate of the Sobek acid-base accounting test and some other static test methods for the assessment of the neutralization potential (NP) of mine wastes. • to determine the effects of the test conditions and procedures on the NP value obtained on the same samples in static NP test. • to provide recommendations for the use of static test procedures and their interpretation for acid rock drainage prediction to assist in the prevention or reduction of pollution to receiving waters. The neutralization potentials of 119 samples of waste rock and tailings have been measured in this study. All samples were tested by the following procedures: • Standard acid base accounting (Sobek et al, 1978) • Standard acid base accounting with different acid additions (based on different fizz ratings) • Modified acid base accounting (based on Lawrence, 1990 and Lawrence and Wang, 1997) • NP by inorganic carbon analysis (Carbonate NP) Some selected samples were tested using Lapakko method (based on Lapakko, 1994). 7 2 . 0 L I T E R A T U R E R E V I E W In this chapter, some of the basic concepts related to acid rock drainage and its prediction are presented. Various static methods used for acid rock drainage prediction, including the Sobek ABA test, the modified ABA test and the test proposed by Lappako (1994), are reviewed. 2.1 REVIEW OF ACID ROCK DRAINAGE 2.1.1 Introduction Exposure of rock or soil containing reactive sulfide minerals to oxidants (typically oxygen) in the presence of water can result in the production of acidic and metal-contaminated surface and ground waters. The run-off from the oxidation and leaching is commonly referred to as acid mine drainage (AMD) or, acid rock drainage (ARD). ARD is a major obstacle to successful reclamation for mining operations throughout the world. Mined rock can contain abnormally high concentrations of heavy metals, which can be released in the sulfide weathering process. If water is available as a transport medium, the resultant drainage can contain products of the acid generation process, typically elevated concentrations of metals and sulfate. This can cause a detrimental 8 impact on water quality in the receiving environment. Uncontrolled ARD emissions can result in significant ecological disruption in sensitive and productive receiving waters. The capability of a particular waste to generate net acidity and produce contaminated drainage is a function of the balance between the potentially acid producing minerals and the potentially acid consuming minerals contained in the material. This balance is further influenced by physical, chemical and biological controls on the relative rate of acid generation and acid consumption. The process by which acid is consumed is known as neutralization. Acidic waters generated by sulfide oxidation in a waste may be neutralized upon contact with acid-consuming minerals. As a result, the water draining from the waste may have a neutral pH and negligible acidity despite on-going sulfide oxidation. However, if the acid consuming minerals are dissolved or coated by other minerals through encapsulation as a result of secondary mineralization, then as acid generation continues, acidic water may eventually drain from the wastes. 2.1.2 Acid Generation The oxidation of sulfur and hydrolysis of iron from sulfur- and iron-bearing minerals is the source of acidity. Minerals or other substances in rocks containing sulfur can be divided into four main types (Norecol, 1992). The first group, sulfide minerals, is regarded as the most important in generation of acidity. Among them, pyrite and pyrrhotite are the most important acid producers due to their abundance. In contrast sphalerite and galena are common sulfide minerals which do not produce acidity. The 9 second group, sulfate-containing minerals, are generally not regarded as acid generators because the sulfur present is already in its highest oxidation state. However, dissolution of limonite containing jarosite (KFe(S04)2(OH)6) or other iron sulfates (e.g. melanterite) in heavily oxidized rock will generate acidity because some iron (II) will oxidize and precipitate as iron (III) hydroxide. The third and the fourth groups, organically-bound sulfur and native sulfur, are oxidized slowly and generally are not sufficiently abundant to be a source of acidity in hard rock ore deposits. The primary ingredients for acid generation are reactive sulfide minerals, water or a humid atmosphere and an oxidant, particularly oxygen from the atmosphere. Generally, acid generation refers to the reaction in the microenvironment around a sulfide mineral grain. The pyrite is the most commonly used mineral to illustrate the acid generation process although other sulfide minerals have different reaction pathways, stoichiometries, and rates. The "standard" reaction for pyrite oxidation in neutral or alkaline conditions can be represented as follows: FeS2 + 7/202 + H 2 0 -> Fe 2 + +2S042" + 2H+ (2-1) The dissolved Fe 2 +, S0 4 2 + , and H + represent an increase in the total dissolved solids and acidity of the water. Unless neutralized, the increasing acidity is often associated with a 10 decrease in pH. If the surrounding environment is sufficiently oxidizing, much of the ferrous iron will oxidize to ferric iron: Fe 2 + + VA02 + H + -> Fe 3 + + LA H 2 0 (2-2) At pH values above 2.3 to 3.5, the ferric iron will precipitate as Fe(OH)3, leaving little 3+ Fe in solution while lowering the pH at the same time due to the release of hydrogen ions: Fe 3 + + 3H20 -> Fe(OH)3 +3H+ (2-3) 3+ Any Fe from Reaction (2-2) that does not precipitate from solution through Reaction (2-3) may oxidize additional pyrite: FeS2 +14Fe3+ + 8H20 -> 15Fe2+ +2S042" +16H+ (2-4) The net reaction for Reactions (2-1), (2-2), (2-3) and (2-4) is: FeS2 +15/402 +7/2H20 -> Fe(OH)3 + 2S042" +4H+ (2-5) Based on these reactions, 1 mole of pyrite will produce 4 moles of H + Certain bacteria may participate the oxidation of sulfide minerals by deriving their energy for cell reproduction from the chemical reaction energy released during the oxidation process and 11 accelerate the rate at which some of the above reactions proceed, thereby increasing the rate of acid generation. Notable work was completed by Kleinmann et al (1981) who discussed the role of bacteria in the acid generating process and presented a simple three-stage model with each stage characterized by the pH of the water in the microenvironment of the sulfide minerals. 2.1.3 Acid Neutralization Acid neutralization minimizes the impacts of acid generation by decreasing levels of acidity, increasing pH towards neutral values, and causing metals in solution to precipitate. There are many minerals that can neutralize acid. Some are more effective than others depending on their relative reactivity and the pH at which they buffer the reaction. These minerals include: carbonates, hydroxides and oxides, and silicates. Carbonates Carbonate minerals are regarded as the most effective natural acid neutralizing agents. They are relatively reactive and can buffer pH in the circum-neutral range. Researchers have primarily focused on role of carbonates because their neutralizing capacity. The most common example of carbonate is calcite (CaC03) which buffers pH near 7. Other common carbonates are dolomite (CaMg(C03)2) and magnesite (MgC03) which are capable of buffering pH to 6 to 7. Another common carbonate is siderite (FeC03). Siderite is an effective neutralizing agent under non-oxidizing conditions because ferrous iron does not oxidize to ferric iron. It is not a useful buffering agent, however, under 12 well-oxidized conditions because the oxidation of ferrous to ferric iron and subsequent precipitation of ferric iron hydroxide produces as much acidity as is consumed by the mineral (Lawrence and Day, 1997) (see also Section 2.4). Discussion of carbonate dissolution and neutralization reactions requires consideration of carbonate equilibrium. From a simplistic viewpoint, the primary forms of aqueous 2 0 carbonate are free carbonate (C0 3 "), bicarbonate (HC03"), carbonic acid (H 2C0 3 ) and dissolved C 0 2 gas. The sum of free carbonate and bicarbonate is usually referred to as carbonate alkalinity. The primary carbonate species are related by the following pH-dependent reactions. H 2 0 + C 0 2 <^  H 2 C0 3 ° <-> HC03" + H + (2-6) HC03" <-> C0 3 2 ' + H + (2-7) At any particular pH, one of these species will be dominant in terms of concentration (Figure 2-1) with H 2 C0 3 ° dominant below a pH of approximately 6.3 to 6.4 (depending on temperature and pressure) and C0 3 " dominant above a pH of approximately 10.3. At pH values between 6.3 and 10.3, the two species will be similar in concentration and significant pH buffering can occur which would allow pH to remain nearly constant despite the addition of acidity or alkalinity. 13 As an example, calcite consumes acidity by a combination of two following reactions to produce bicarbonate or carbonic acid: C a C 0 3 + H + -> C a 2 + + HCO 3 " (2-8) C a C 0 3 + 2 H + -> C a 2 + + H 2 C 0 3 ° (2-9) The former reaction is important in weakly acidic to alkaline environments whereas the latter occurs when conditions are very strongly acidic (Lawrence and Day, 1997). Figure 2-1. Relationship of pH to Concentrations of Carbonate Species (from Freeze and Cherry, 1979). 14 These reactions and the capacity for pH buffering have major implications for neutralization of acid drainage. For example, if C0 3 " from the dissolution of a carbonate mineral is continuously added to acidic water (e.g., at pH 2), the pH will slowly increase towards 6 through the reverse reactions of Equations (2-6) and (2-7) forming H 2 C O 3 0 by _l_ 2 consuming 2 moles of acidity (H ) for each mole of C0 3 " . Around pH 6.3, HC03" begins forming in preference to H 2 C0 3 °. Because HC03" represents a consumption of only 1 mole of acidity for each mole of carbonate, neutralization beyond this point becomes less efficient. As C0 3 " continues to be added to the water, the pH begins to rise above 6.4, however, this is resisted by H 2 C0 3 ° which begins to break down to HC03" and releasing acidity according to Equation (2-6). This release of acidity requires additional carbonate to raise the pH above 6.4. That means neutralization with carbonate to pH 7 requires significantly more carbonate than for neutralization to pH 6. Because a pH near 6 may not be sufficiently neutral to ensure the protection of freshwater life and the precipitation of metals to acceptable levels, carbonate consumption to reach a pH of 7 to 8 may often be a more reliable target for neutralization, in general requiring significantly more carbonate. Hydroxides and oxides Hydroxides and oxides can also neutralize acid and buffer solutions, although at a lower pH than carbonate minerals. Examples are iron hydroxide, which buffers pH between 3.0 and 3.5, and aluminum hydroxide which buffers pH between 4.5 and 5.0 (Lawrence and Day, 1997). The reactions are as follows: 15 Iron hydroxide buffers pH between 3.0 and 3.5 Fe (OH)3 + 3H+ -> Fe 3 + + 3H20 (2-10) Aluminum hydroxide buffers pH between 4.5 and 5.0 Al(OH)3 + 3H+ = A l 3 + + 3H20 (2-11) Silicates Silicates are the largest mineral group and comprise a extensive variety of minerals composed of silicon combined with other common elements such as iron, aluminum, potassium, sodium, calcium and magnesium. About a fourth of the known minerals are silicates, though many of them are very rare. They are the most important rock forming minerals and thus make up the bulk of the earth's outer shell. Rogers (1937) divided silicate minerals into more than ten groups. They have different reactivities under weathering. Figure 2-2 clearly shows the order of the silicate minerals arranged from most susceptible to weathering to the least (Sherlock et al (1995) modified from Goldich (1938) and Williams (1990)). The buffering pH of silicate minerals depends on the solubility of the metals released by interaction between the mineral and acidity conditions (Lawrence and Day, 1997). For example, the buffering capacity of a relatively simple calcium silicate such as wollastonite (CaSi03) would be controlled by the solubility of calcium minerals, assuming buffering occurs in equilibrium with the atmosphere (Reaction 2-12). would be expected to be buffered at near neutral conditions. 16 ThepH CaSi03 + H 2 0 +2H+ -> Ca 2 + + H 4Si0 4 (2-12) A similar conclusion would be expected for magnesium silicate minerals. Alumino-silicates release aluminum when interacting with acid. For example, for kyanite: However, aluminum solubility is controlled by the solubility of aluminum hydroxide which buffers pH around 4.5 (Equation 2-14). So, the importance of mineralogy is evident for understanding the buffering capacity of minerals. Silicate neutralization in ARD systems has been identified by elevated concentrations of silica and aluminum in tailings water and waste rock drainage (Morin, 1988; Alpers and others,1990; Blowes et al, 1992; Blowes and Ptacek, 1994). Morin et al (1988) suggest that ARD has elevated silica and aluminum concentrations due to alumino-silicate mineral dissolution. Blowes and Ptacek (1994) also suggest that the source for aluminum ions for gibbsite (Al(OH)3) precipitation, during the step-wise pH decrease, is alumino-silicate dissolution. Al 2Si 20 5(OH) 4 + 6H+ -> 2A13+ + 2H4Si04 + H 2 0 (2-13) A l 3 + + 3H20 -> Al(OH)3 + 3H+ (2-14) 17 2.1.4 Development of ARD The discussion so far has largely been concerned with reactions taking place in the microenvironment of the oxidizing and neutralizing minerals. The development of ARD and its fate in the receiving environment is, however, made more complex by a series of chemical, physical and biological oxidation reactions along the flow-path (Figure 2-3). Therefore, the ultimate drainage water quality depends on characteristics controlling contaminant release, rate of mineral oxidation and acid generation, rate of metal leaching, rate of acid neutralization, solubility of metal species, accumulation of oxidation products and the reactions along the flow path. Olivine Augite Hornblende Biotite Potash feldspar Muscovite Quartz Calcic plagioclase Calci-alkali plagioclase Alk-calcic plagioclase Alk-plagioclase Figure 2-2. The mineral stability series in weathering (Sherlock et al, (1995), modified from Godich (1938) and Willams (1990)) SITE OF OXIDATION pyrite -» Ferrous iron +Acid Ferrous iron -> Ferric iron I REACTIONS ALONG FLOWPATH Leaching of sulfides and oxides —> metals in solution Acid neutralization by carbonates and silicates Metal precipitation / Secondary reaction products Iron hydrolysis Gypsum precipitation I INTERACTION OF DRAINAGE WITH EVIRONMENT Physical, Chemical, Physico-chemico and Biological Controls I RECEIVING WATERS Figure 2-3: The simplified ARD development and the reactions along flow-path (Lawrence and Day, 1997) 19 2.1.5 Implications of Neutralizing Mineral Weathering for NP Determination The reactions and factors involved in rock weathering as a result of acid neutralization through dissolution and alteration processes discussed in the preceding section have important implications in the acid neutralization capacity determination. The static test neutralization potential (Lab-NP) procedure is a measurement of the capacity of a finely-crushed sample to neutralize strong acidity. Compared to AP measurement, NP determination is more complex. For AP, there is a clearly defined contributing mineralogy, i.e., sulfides and usually one or two dominant minerals, pyrite or pyrrhotite. For NP, many common rock forming minerals are capable of producing some alkalinity, but in widely varying reactions and rates. Even for the same sample, alkalinity production can be changed by the measurement procedure, the weathering or simulated-weathering conditions, physical properties, the acid generation rate and time. The amount of variation is strongly affected by the type and relative quantities of the potentially NP contributing minerals. Sherlock et al, (1995) discussed the role of carbonate and silicate minerals in neutralizing acid generated within a sulfuric mining waste. They suggested that if calculations of the buffer intensity and neutralizing capacity of simple carbonate and silicate systems were carried out, there would be an indication that the acid neutralizing capacity of silicate minerals is greater than the carbonates and is thermodynamically possible. The silicate reactions, however, are slower than the more reactive carbonates. It is for this reason that 20 the most important buffering that occurs within near surface natural waters is by the carbonate system. Within ARD conditions, once the carbonate neutralizing capacity is depleted, silicate dissolution can play a role in long-term acid neutralization. Kwong (1993) gave a grouping of minerals according to their acid neutralization capacity at pH 5, after Sverdrup (1990) (Table 2-1) and indicated that because of the fast reaction rate, carbonate minerals, specially calcite, have been widely quoted in the acid rock drainage literature as the only species that possess any practical neutralization potential. However, carbonates are dominant only in few rock types like limestone, dolomite and marble while the majority of geologic materials are composed of silicates. To assess the buffering capacity of mine wastes, silicate minerals therefore must also be considered. For carbonate minerals, the difference between acid generation and neutralization rates is often not significant. However, the difference is very important when the NP comes from slowly dissolving alumino-silicate minerals, which will only contribute significant effective Field-NP when the in-field rate of acid generation is also slow. Price (1997) has defined "Effective Field NP" as the ability of a potential NP source to maintain a neutral drainage chemistry. If the acid generation rate is relatively fast, the aluminosilicate minerals may not react fast enough to neutralize the acidity, and thus these minerals would not contribute significantly to the effective Field-NP. As field performance can depend in large part on the reaction rates, the evaluation of Lab-NP results should include an assessment of the reaction rates of minerals contributing to the lab-determined value. 21 If non-carbonate minerals are an important potential NP source, the prediction of the effective Field-NP requires kinetic test information (Price, 1997). Table 2-1. Grouping of Minerals According to their Acid Neutralization Capacity at pH 5 (Kwong, 1993, after Sverdrup, 1990) Mineral Group Typical Minerals Relative Reactivity Dissolving calcite, aragonite, dolomite, magnesite, brucite 1.000 Fast weathering anorthite, nepheline, forsterite, olivine, garnet, jadeite, leucite, spodumene, diopside, wollastonite 0.400 Intermediate weathering sorosilicates (epidote, zoisite), pyroxenes (enstatite, hypersthene, sugite, hedenbergite), amphiboles (hornbende, glaucophane, tremolite, actinolite, antophyllite), phyllosicates (serpentine, chrysotile, talc, chlorite, biotite) 0.020 Slow weathering plagioclase feldspars (albite, oligoclase, labradorite), clays (vermiculite, montmorillonite) 0.010 Very slow weathering K-feldspars, muscovite 0.010 Inert quarts, retile, zircon 0.004 22 2.3 ARD PREDICTION AND STA TIC PREDICTION TESTS 2.3.1 Introduction The purpose of ARD prediction testing is to provide sufficient data to satisfy the mine operators, owners and the regulatory authorities that the potential for ARD generation can be predicted and controlled. Mining companies are required to provide evidence that waste materials to be generated during operation can be stored in a manner that will not result in ARD both during operation and long after mine closure. On the other hand, regulators are required to develop and apply regulations that are both fair to the mine operator and protective of the environment. ARD prediction is important from both environmental and economic perspectives. Information derived from properly conducted and interpreted static tests, in conjunction with experience, can form the basis for preliminary estimates of metal leaching and ARD. The early identification of "problem" wastes and development of an appropriate waste management plan can significantly reduce long term environmental problems and remediation costs. Early identification and incorporation of control measures can also reduce the financial liabilities of maintaining long term collection and treatment facilities,. It is important to the mining company as well as to the regulatory authorities to do sufficient, appropriate testing to ensure that all potential problems have been identified and addressed. 23 Several ARD prediction tests and methods are in use or have been proposed which differ in complexity of procedure, complexity of data interpretation, time required to achieve a predictive result, and the cost of carrying out the test. Broadly, ARD prediction test procedures can be divided into two categories, static tests and kinetic tests. Static tests are designed primarily to examine the balance between the acid producing components and the acid consuming components of a mine waste sample. The term static is used since the tests do not consider the relative rates of acid production and consumption. The objective of kinetic tests is to predict the long term weathering characteristics of a mine waste material as a function of time. From a geochemical perspective, acidic drainage can be viewed as the result of competition between acid-generating and acid-neutralizing minerals, with the dominant minerals regulating the chemistry of water passing over the material (Morin and Hutt, 1994). Acid producing minerals are generally reactive sulfide minerals. Acid consuming minerals are primarily carbonate minerals although hydroxides and silicates can also provide neutralization potential as discussed in Section 2.1.3. Static tests involve laboratory methods to determine the acid consuming capacity of the sample, termed the Neutralization Potential or NP, and the acid producing potential, termed the Acid Potential or AP. The difference between the two values is termed the Net Neutralization Potential or NNP, where NNP = NP-AP. The ratio between the two values is termed the NP/AP Ratio or NPR. NP, AP and NNP are expressed in consistent units (e.g., kg CaC0 3 equivalent/tonne of sample) to facilitate comparison of the values. 24 A number of static test procedures have been developed to provide quick and inexpensive estimates if a mine waste will produce acidic drainage. The results are commonly used as a first-cut screening in the process of mine waste characterization. Acid base accounting has proven to be a valuable tool in acid drainage assessments for nearly 20 years and is commonly used. The Standard Acid-Base Accounting (Sobek et al 1978) and the Modified Acid-base Accounting Test originally proposed by Lawrence (1990) and modified by Lawrence and Wang (1997) are the most widely used static test procedures in recent years. These methods each address the same variables but with variations in the procedure. Several other static methods can be found in the literature for the initial assessment of ARD potential of waste samples. For example, the B. C. Research Initial Test (Duncan and Bruynesteyn, 1979) which was not evaluated in this study and a method proposed by Lapakko (1994) are used in some evaluations. These two methods are the similar in that they both use sulfuric acid to titrate a pulp of the sample down from its natural pH to a specified endpoint. The titration endpoint is 6.0 for Lapakko Method and 3.5 for the B.C. Research Initial Test. Lapakko (1994) selected pH 6 as the endpoint since it is a commonly applied water quality standard. Other pH values could also be used, depending on the drainage pH required at a specific site. In the B. C. Research Initial Test, the end point pH 3.5 is based on an assumption that this represents the limit above which iron and sulfide oxidizing bacteria such as Thiobacillus ferrooxidans are not active. Therefore, if the theoretical acid production is not sufficient to lower the pH to 25 below pH 3.5, then biochemical oxidation of the material will not occur, and the formation of ARD is unlikely. 2.3.2 The Standard Acid-Base Accounting (Sobek Method) Principles The objective of acid-base accounting is to analytically estimate the quantities of minerals capable of generating acid and minerals that may naturally consume acid when weathered. Acid base accounting comprises two distinct measurements: calculation of the acid potential of the sample and determination of the neutralization potential of a sample. The acid potential is determined by analyzing for total sulfur and calculating AP by assuming (1) total conversion of sulfur to sulfate, and (2) 4 moles H + are produced per mole pyrite oxidized. The neutralization potential is determined by treating small amount of finely-ground sample with excess The Standardized hydrochloric acid and heating to ensure complete reaction. A fizz test is employed to ensure that the amount of acid added is sufficient to react with all of the acid consuming minerals present. The residual acid is titrated with The Standardized base to pH 7 to allow calculation of the calcium carbonate equivalent of the acid consumed. 26 The relationship between the two values, the net neutralization potential (NNP) and NP/AP Ratio (NPR), allows classification of the sample as potentially acid consuming or producing. Calculations The acid potential AP of the sample is given by: AP = Percent total sulfur * 31.25 AP is estimated by measuring the total quantity of sulfur in a sample. This is usually expressed as percent sulfur by weight but must be converted to calcium carbonate units for used in acid-base accounting. This is achieved by writing two ideal reactions for net acid generation: oxidation of iron disulfide: FeS2 + 15/4 0 2 + 7/2 H 2 0 -> Fe(OH)3 + 2S042" + 4H + (2-15) and acid consumption by calcium carbonate: CaC0 3 + 2H + -> Ca 2 + +C02 +H20 (2-16) 27 Based on these reactions, 1 mole of sulfur produces 2 moles of H + , which can be neutralized by 1 mole of CaC03. Therefore, 1 mole of sulfur is theoretically equivalent to 1 mole of CaC0 3. The weight equivalency is 1 g S to 3.125 g CaC0 3, therefore the sulfur concentration (in percent) is multiplied by 31.25 to yield maximum potential acidity (MP A) in kg CaC03/t of rock. The neutralization potential, NP, of a sample is given by: NP = 50*a*(x-(b/a)*y)/c where: NP = neutralization potential in kg CaC03 equivalent per tonne of material a = normality of HC1 b = normality of NaOH c = sample weight in grams x = volume of HC1 added in ml y = volume of NaOH added to pH 7.0 in ml "Fizz" Test In the fizz test, two or three drops of dilute (25%) hydrochloric cold acid is added to a few grams of the finely ground sample. The degree of audible fizz and visual frothing allows the selection of a fizz rating (Table 2-2) which in turn is used to select the volume and normality of hydrochloric acid be used in the digestion stage. The objective of the fizz test is to assess how much carbonate is present in a sample so that sufficient acid to 28 complete reaction with the acid consuming constituents in the sample can be provided. A rapid effervescence with the acid indicates that calcite is present. Less reactive carbonate such as dolomite and magnesite might not immediately provide effervescence with the cold acid. Siderite and ankerite will only react with heated acid (Deer et al., 1966). To ensure that sufficient acid has been added, the Sobek procedure indicates that if less than 3 ml of base which has the same strength as the acid used, is needed in the back-titration to maintain a pH of 7.0, the HC1 added was not sufficient. If this is the case, the test should be repeated using the next higher volume or strength of acid. There is no provision in the Sobek test, however, to account for an excessive addition of acid. Table 2-2. Volume and Normality of HC1 for Use in the Sobek NP Determinations Based on the Fizz Rating (2g sample) Fizz Rating Acid Normality Acid Volume (ml) None 0.1 20 Slight 0.1 40 Moderate 0.5 40 Strong 0.5 80 It is asserted in this thesis that the determination of the fizz rating in practice is largely subjective and could be a matter of opinion between different technicians assessing the same sample. In addition, other factors such as distractions in the laboratory can lead to uncertain assessment of the fizz rating. For a particular sample, the fizz rating could be 29 one of three values: the "correct rating", an underestimated rating and an overestimated rating. The quantity of acid added to the pulp in the digestion stage will vary accordingly. In this study, therefore, the effect of different fizz ratings on the NP value were studied by testing all samples at three different levels of acid addition in the Sobek procedure. Assumptions and Limitations with the Estimation of Sobek NP Several assumptions and limitations made in Sobek NP estimation cannot be ignored if results are to be interpreted meaningfully and valid conclusions are to be drawn. They are as follows: • The sample is finely-ground. The surface area and mineral exposure of a mineral is therefore, be changed, as is the mineral's reactivity. • The test involves both a very strong acid and heating, neither of which occur in neutral pH weathering, and which may overestimate the NP contribution of some minerals, such as slow weathering silicates. • The Sobek NP value could be dependent on the fizz test result (see Section 2.3.2.3). • It is assumed that minerals capable of neutralizing hot hydrochloric acid will actually consume sulfuric acid produced from rock weathering. • It is assumed that the laboratory neutralization reaction is comparable to natural neutralization reactions. Unfortunately, data comparing laboratory neutralization potential with natural neutralization of acid is very limited. For example, some 30 silicates are likely to be digested by the laboratory test but the actual ability of these minerals to neutralize acidic drainage is not well documented. • In some cases, minerals which are not naturally net acid-consuming will consume acid in the Sobek NP test. For example, the mineral, pyrrhotite FeS, will consume acid with the release of H2S when it reacts with hydrochloric acid: Every mole of sulfur consumes two moles of acid and the hydrogen is mostly lost as volatile hydrogen sulfide. This reaction could result in higher neutralization potentials 2+ which should in fact be accounted for in the AP estimation. However, if the Fe 3+ produced in the reaction were to be oxidized to Fe and subsequently precipitated, the overall reaction could produce as much acid as is consumed: FeS + 2HC1 -> Fez + 2C1" + H2S (2-17) Fe 2 + + l/40 2 + 5/2H20 -> Fe(OH)3 + 2H+ (2-18) It appears that there are several minerals that can produce false overestimation of neutralization potential. In this regard, neutralization potential tests are much more likely to produce anomalous results than AP determinations. 31 Another mineral, iron carbonate, may create anomalous results for NP determination using hydrochloric acid. Brown et al. (1995) examined problems with the determination of NP values. They indicated that in the Sobek procedure, siderite, if present, would react quickly with acid indicating that rock is an alkaline contributor (Morrison et al., 1990; Cargeid, 1981; Meek, 1981; Wiram, 1992). However, upon complete weathering (Equations 2-19 to 2-22), siderite is a neutral (Shelton et al., 1984; Meek, 1981) to slightly acid-producing rock (Frisbee and Hossner, 1989; Cravotta, 1991; Doolittle et al., 1992): Because HC1 is used for digestion in the NP determination, the acid rapidly reacts with the carbonate and neutralizes 2 moles of alkalinity: The initial result is that siderite contributes 2 moles of alkalinity (Equation 2-20). However with time, ferrous iron (Fe ) oxidizes to ferric iron (Fe ) (Equation 2-21), and ferric iron can hydrolyze, forming Fe(OH)3 and precipitate (Equation 2-22): FeC0 3 + l/402 + 5/2H20 <-> Fe(OH)3 + H 2 C0 3 (2-19) FeC0 3 + 2HC1 -> FeCl2 + H 2 C0 3 (2-20) FeCl2 + 1/4 0 2 + HC1 -> FeCl3 + 1/2 H 2 0 (2-21) FeCl3 + 3NaOH -> Fe(OH)3 + 3NaCl (2-22) 32 The outcome of Equations (2-20) to (2-22) are the production of 3 moles of acidity (HC1) and 3 moles of alkalinity (NaOH ) are consumed. This means that the acid and alkalinity effectively neutralize each other yielding a resultant NP for siderite of zero with no net acidity or alkalinity produced. The Sobek NP procedure does not allow sufficient time for ferrous iron oxidation and ferric hydroxide precipitation, and therefore this procedure accounts for only the initial reaction resulting in 2 moles of alkalinity (Equation 2-20). When siderite is present in an waste sample and insufficient time is given for complete iron oxidation and precipitation during back titration, erroneously high NP values can be generated providing inaccurate NP information. Morrison et al (1990) pointed out that because the Fe 2 + will be slow to oxidize to Fe 3 + and precipitate as Fe(OH)3 (Equation 2-21, 2-22), unstable endpoints to the back titration in Sobek et al (1978) procedure will occur. Shelton et al. (1984) found that siderite reacts slowly with dilute acid at room temperature. Siderite's slow reaction could result in a lower fizz rating which would results in too little acid being used in the digestion process (Morrison et al. 1990). If a weaker strength and lower amount of acid is used in the digestion process, the quantity of alkalinity in a rock may be underestimated. Morrison et al. (1990), Williams (1992), and Meek (1981) suggest adding a small quantity of 30% hydrogen peroxide (H202) to the filtrate of a digested sample prior to the back titration in determining NP. Peroxide addition causes the ferrous iron to oxidize to ferric iron before back titrating. The resulting ferric iron is then precipitated as Fe(OH)3 upon titration and the solution yields a more accurate NP value. 33 Morin (1990) also examined the problems in the determination of Neutralization Potential. He indicated that the Sobek ABA procedure of NP determination introduces two major uncertainties that can affect the accuracy of the NP value and ability to interpret the value. These uncertainties are the impact of the large range of pH variation during the acid soak and the base titration, and the impact of the length of time during which the sample is immersed in excess acid. 2.3.3 Modified Acid Base Accounting Test Principles As with the Sobek acid base accounting method, the fundamental principals of modified acid base accounting comprise two distinct measurements: calculation of the acid potential (AP) of the sample and determination of the neutralization potential (NP). The difference between the two values, the net neutralization potential (Net NP) or the NP/AP Ratio (NPR), allows classification of the sample as potentially acid consuming or producing. In the modified ABA procedure of Lawrence and Wang (1997), AP is calculated from sulfide sulfur content. The sample can be analyzed for sulfide sulfur or calculated by the difference of total sulfur and sulfate sulfur. In some cases, other sulfur species such as that associated with the mineral barite (not distinguished in a typical sulfate analysis), which do not contribute to the acid potential, might be identified and an appropriate correction made to the sulfide sulfur calculation. Generally, the sulfate is often a product 34 of acid generation but is not considered acid-generating in itself. So, the use of total sulfur for AP calculation can sometime lead to erroneously high results. The value of this refinement is obvious for samples that contain high concentrations of sulfate minerals such as gypsum. With regard to the NP, the Modified ABA test was originally developed (Lawrence, 1990) to reduce the tendency to overestimate NP values perceived to be obtained in the Sobek procedure. This is achieved by performing the hydrochloric acid digestion for 24 hours at room temperature or slightly higher (25-35°C) and by controlling the addition of acid so that the pH of the pulp after digestion is in a specific range (2.0-2.5). In addition, the end point of the back titration is 8.3, being the usual endpoint for acidity titrations, corresponding to the stoichiometric equivalence point for carbonate/bicarbonate in natural waters in which carbonic acid is the most dominant weak acid. Digestion at the lower temperature reduces a perceived bias towards the alkaline side giving an overestimation of the neutralization capacity of some waste materials at the high digestion temperature of the Sobek test. Similarly, the target pH range specified following the digestion step is intended to prevent over-reaction and to provide consistent conditions at the end of digestion between different tests. Calculations The calculation of AP and NP of a sample in the modified ABA test is the same as for the Sobek AP and NP (Section 2.3.2.2 ) except that for the AP calculation, sulfide-sulfur is 35 used instead of total sulfur and that for the NP calculation, the endpoint pH 8.3 is used instead of 7. "Fizz Test" As with the Sobek procedure, a fizz test is employed in the modified acid base accounting procedure to allow selection of the acid normality and volume (Table 2-3). However, the fizz rating has much less effect on the NP value compared with the Sobek method because the endpoint pH of pulp in the digestion is controlled to 2.0 to 2.5 in order to standardize the degree of excess acid. Table 2-3. Volume and Normality of HC1 for Use in Modified NP Determinations Based on the Fizz Rating (2g sample) Fizz Rating Acid Normality Acid Volume (ml) at time = 0 h at time = 2 h None 1.0 1.0 1.0 Slight 1.0 2.0 1.0 Moderate 1.0 2.0 2.0 Strong 1.0 3.0 2.0 From Tables 2-2 and 2-3, it can be noted that there are two significant differences between the fizz tests of the Sobek and the Modified procedures. Firstly, the acid is added in two increments in the Modified method so that the degree of excess acidity during digestion is reduced. Secondly, the acid is added at small volumes of a higher 36 normality (1.0N) to the sample pulp. This has added considerably to the ease and accuracy of carrying out the test. Assumptions and Limitations with the Estimation of Modified NP Assumptions and limitations in the determination of modified NP are as follows: • The sample is finely-ground. The surface area and mineral exposure of a mineral is changed. This can affect the mineral's reactivity. • The test is only carried out for a limited duration. Thus, if the field rate of acid generation is slow, it may underestimate the NP content of slowly dissolving aluminosilicate minerals. • It is assumed that minerals capable of neutralizing hydrochloric acid in room temperature will actually consume sulfuric acid produced from rock weathering. • It is assumed that the laboratory neutralization reaction is comparable to natural neutralization reactions. • In some cases, minerals which are not naturally net acid-consuming will consume acid in the modified NP test (Section 2.3.2.4). Even though the procedure has been modified to reduce the possibility of large variations in acidic conditions, there is still some uncertainty as to the range of acidity during the digestion. 37 2.3.4 The Procedure of NP Determination Proposed by Lapakko Principles Lapakko (1994) suggested a procedure in which the acid digestion is carried out only to a pH of 6.0. Therefore, the neutralization potential available above this pH represents the amount of acid that a mine waste could neutralize while maintaining drainage pH in a range that meets water quality The Standards. In this way, the contribution of silicate minerals to NP would be ignored. Lapakko method is an attempt to recognize that if calcite or other carbonates coexist with silicate minerals, the calcite will preempt the role of acid neutralization capacity through the alteration processes. This is because the alteration processes for silicates are much slower than the calcite dissolution. It suggests that in the short term, the carbonates are important in determining the resultant drainage quality from waste rock piles or tailings impoundments and, once depleted, silicate alteration becomes more important in the long term. According to Lapakko, the most effective minerals for neutralizing (consuming, buffering) acid are those containing calcium carbonate and magnesium carbonate, examples of which are calcite (CaC03), magnesite (MgC03), dolomite (CaMg(C03)2), and ankerite (CaFe(C03)2). When the pH is above 6.3, the following reactions are dominant: CaC03(s) + H+(aq) = HC03"(aq) + Ca2+(aq) (2-23) 38 MgC03(s) + H+(aq) = HC03"(aq) + Mg2+(aq) (2-24) When pH is below 6.3 the following reactions are dominant: CaC03(s) + 2H+(aq) = H2C03(aq) + Ca2+(aq) (2-25) MgC03(s) + 2H+(aq) = H2C03(aq) + Mg2+(aq) (2-26) The rate of magnesium carbonate dissolution is reported to be slower than that of calcium carbonate (Rauch and White, 1977). As previously discussed, iron carbonates will provide no net neutralization of acid. Dissolution of minerals such as anorthite (Reaction 2-27, Busenberg and Clemency, 1976) and forsterite (Reaction 2-28, Hem, 1970) can also neutralize acid, but their dissolution rate (and associated rate of acid neutralization) is slow in the neutral pH range. These minerals dissolve more rapidly as pH decreases and, therefore, provide more acid neutralization under acidic conditions. In this study, Lapakko NP was determined by titrating a stirred mixture of mine wastes and distilled water with different normalities of sulfuric acid using a pH controller. The CaAl2Si208(s) + 2H+(aq) + H 2Q = Ca2+(aq) + Al2Si205(OH)4(s) (2-27) Mg2Si04(s) + 4H+(aq) = 2Mg2+(aq) + H4Si04(aq) (2-28) 39 titration was continued until pH 6 was reached and less than 0.1 ml of acid was added over a period of 4 hours. Calculation The neutralization potential, NP, in kg CaC03 per tonne of material is given by: NP = a*b*50.05/c Where:NP = neutralization potential in kg CaC0 3 equivalent per tonne c = sample weight in grams a = volume of H 2 S0 4 added in ml. b = normality of H 2 S0 4 added in ml. Assumptions and Limitations of NP Determined by Lapakko Method Assumptions and limitations of NP determined by Lapakko procedure are as follows: • The sample is finely-ground. The surface area and mineral exposure of a mineral is changed. This would affect the mineral's reactivity. • It only measures the NP which contributed by calcium carbonate and magnesium carbonate. The test does not measure other possible sources of alkalinity such as reactive silicates. As a result, the Lapakko NP might underestimate the NP value, especially when acid generation is very slow. • It is assumed that the laboratory neutralization reaction is comparable to natural neutralization reactions. 40 • To ensure that the addition of acid does not drop the pulp pH below 6, very dilute acid has to be used at a very low rate of addition. Compared to the Sobek ABA and the modified ABA test procedures, the NP determined using the method proposed by Lapakko is, therefore, a much more time consuming procedure. 2.3.5 Interpretation of Static Test Results The interpretation of ABA test results is based on both the difference and ratio between the neutralization potential (NP) and acid potential (AP). The original interpretation of static tests was to calculate the difference termed the Net Neutralization Potential or Net NP or NNP. By convention, NNP = NP-AP, so that a positive value of NNP indicate that the sample has more acid consuming constituents than acid producing ones. The sample is therefore classified as a potentially acid consuming material. Similarly, a negative NNP value indicates that the sample has a surplus of acid producing constituents and is therefore classified as a potential acid producing material. In practice, different jurisdictions have used different guidelines to asses the acid producing or consuming potential based on NNP. For examples, in British Columbia before 1997, NNP > +20, non acid generating; 20 > NNP > 0, uncertain; NNP <0, acid generating. More recently, interpretation of ABA test by calculating the NP:AP ratio, has become a more favored method as this value provides a clearer appreciation of the relative quantities of AP and NP. Table 2-4 provides an example of two rock types which have 41 very different sulfur contents (Lawrence and Day, 1997). Irrespective of the NP value, sample #2 would have to be thought of a potential source of acidity due to its high sulfur value. Nevertheless, the NNP value of both samples is very similar. The distinction between the two samples is only evident when the NP/AP ratio is considered. Table 2-4. Comparison of Static Test Interpretation by NNP and NP/AP AP NP NNP NP/AP Waste Rock #1 3 15 12 5.0 Waste Rock #2 128 142 14 1.1 Table 2-5. Screening Criteria Based on ABA Test Results POTENTIAL FOR ARD INITIAL NPR SCREENING CRITERIA COMMENTS Likely < 1:1 Likely ARD generating. Possibly 1:1-2:1 Possibly ARD generating if NP is insufficiently reactive or is depleted at a faster rate than sulfides. Low 2:1-4:1 Not potentially ARD generating unless significant preferential exposure of sulfides along fracture planes, or extremely reactive sulfides in combination with insufficiently reactive NP. None >4:1 No further ARD testing required unless material are to be used as a source of alkalinity. 42 As with the NNP method, different jurisdictions use different guidelines to asses the acid producing or consuming potential based on NPR. In British Columbia, Acid-Base Accounting Screening Criteria are as follows (Price 1997): Materials with a sulfide-S content less than 0.3% and a subsoil pH greater than 5.5 require no further ARD testing and are considered safe to excavate if there are no other metal leaching concerns. Where materials are mineralized, the full suite of ABA testing should be conducted. Screen criteria based on ABA test results are presented in Table 2-5. Typically, data for acid base accounting analysis are presented graphically to visually represent the different category of material as from in Table 2-5. Graphs can be simple NP vs AP plots, or perhaps more favorably represented as NPR-S plots as shown in Figure 2-4. From Table 2-5, samples with NP/AP ratio greater than 4 can be judged to be of no concern with respect to ARD potential and no further testwork is required, unless the materials are to be used as a source of alkalinity. Here, the ratio of 4:1 is a conservative screening criteria which will be higher than the maximum NPR of acid drainage generating materials as documented by MEI. It is selected to ensure the detection of all sites where there is an unfavorable balance between acid generation and neutralization 43 reactions or where the composition of the reactive fraction varies significantly from the analysis of the entire sample. 1000 100 ; : : : : : i * ! * 3 : ;  1 ; : : : : : ! * * * ; : ; 9 I * $/ * * ****=! •til * * ** * * * * * * * * * ** * * =t * * * * * * * * * * * * * 0.001 0.01 0.1 0.3 1 10 S (%) Figure 2-4. The relationship of NP:AP Ratio and Sulfide-S content (after Soregaroli and Lawrence (1997)) Without additional information, samples with a NPR less than 4 will be considered to have an uncertain ARD potential. Where the acid rock drainage potential of a waste material or geological unit is uncertain, it will be considered potentially acid generating until the prediction can be refined through further testing, usually by kinetic testing and local environmental field studies. The type and amount of additional testwork required for material will, to some degree, depend on the ARD potential. For example, the designation of low ARD potential NPR 2 to 4 will be changed from low to non-ARD 44 generating when it is shown that either the sulfides will not be preferentially exposed or that the NP is sufficiently reactive. Typically, the choosing of possibly ARD potential NPR between 1 and 2, With very slowly reacting sulfides and significant slow release alkalinity, ARD may not occur in materials with an NPR less than one. It is cautioned that acid-base accounting on its own provides only a rough assessment of the potential for acid drainage. The information derived from testing can form the basis for preliminary estimates of metal leaching or the ARD potential particularly when results are considered in conjunction with detailed test conditions and procedures, previous experience, the acknowledgment of the rock and mineral reactivity, the detailed historic site characterization and monitoring, as well as field environmental studies. From the preceding discussion, it appears that the ABA criteria in B.C are reasonable because the local environment conditions are considered. In any case, more accurate site and material-specific interpretation or testing should be used to develop less conservative and more refined materials handling criteria. 45 3 . 0 E X P E R I M E N T A L P R O C E D U R E S 3.1 SAMPLES AND SAMPLE PREPARA TION A total of 119 samples were tested in this study. I l l samples (85 waste rock and 26 tailings) were obtained for 12 operating or proposed mines in the Philippines, Papua New Guinea, Chile, Canada and the United States. Another 8 samples were certified reference standards (concentrates, ores and other metallurgical samples) from the Canada Center for Mineral and Energy Technology (CANMET). One of the reference standard materials, NBM-1, has recently been produced as a reference material for static test calibration (Leaver et al, 1994). This sample will be discussed in Section 4.1.2 because of its special interest. Except for the reference standards, all the samples were code numbered as follows: (mine number)(sample number)-(type of sample). For example, waste rock sample number 1 from mine number 5 is coded 501-WR; tailings sample number 2 from mine number 3 is coded 302-T. The reference standards are given their CANMET identifiers. Samples were prepared as required for testing as follows: • Most of the samples were received as assay or ABA rejects and were therefore already pulverized, with a typical size range of 100% minus 60 mesh to 80% minus 200 mesh. In these cases, no further sample preparation was required. 46 • Waste rock samples received in larger sizes were jaw crushed/cone crushed/pulverized as required to approximately 80% minus 200 mesh. • Tailings samples were air dried and tested in the as-received size. 3.2 DETERMINATION OF ACID GENERATING POTENTIAL In order to determine the Acid Potential (AP) of a sample, a sulfur analysis must be performed. As discussed in Section 2.1.2, a sample may contain several forms of sulfur. Among them, sulfide minerals are regarded as the most important in generation of acidity. In the Sobek method, the AP is calculated on the basis of total sulfur. In the modified method, AP is calculated on the basis of sulfide-sulfur which normally is determined from sulfide sulfur analysis or calculated by the difference of total sulfur and sulfate sulfur. The purpose of using sulfide sulfur is to overcome AP overestimation in the Sobek method. Since the emphasis of this study was the determination of NP, only total sulfur analyses of the samples were used to determine AP for all the test methods. Total sulfur was determined either by using classical acid digestion /barium sulfate precipitation or by a Leco induction furnace in a previous study (Lawrence 1997c). Sulfur species analyses were not carried out. 47 3.3 NEUTRALIZATION POTENTIAL BY THE SOBEK ABA METHOD 3.3.1 Standard Method In the Standard Acid Base Accounting test, all the samples were tested following the Sobek et al (1978) procedure precisely, with acid additions selected exactly according to the actual fizz rating. The principles, calculations and interpretation of results have been discussed in Section 2.3.2. The detailed procedure used is described in Appendix I. 3.3.2 Use of a Different Fizz Rating in the Sobek Method In these series of tests, the Sobek procedure was followed. However, each sample was tested under three different fizz ratings. If a particular sample was judged to have no fizz (standard), additional tests were carried out using acid additions corresponding to the slight (+fizz) and moderate (++fizz) fizz ratings. If a sample was judged to have a fizz rating of moderate (standard), the additional tests were carried out using acid additions corresponding to slight (-fizz) and strong (+fizz) fizz ratings. If a sample was judged to have a strong fizz (standard), the additional tests were carried out using acid additions corresponding to slight (--fizz) and moderate (-fizz) fizz ratings. In a few cases, insufficient sample did not allow testing at the 3 different fizz ratings. The rationale for this series of tests was discussed in Section 2.3.2.3. 48 3.3.3 Back Titration Curves Obtained from the Sobek Tests According to the Sobek procedure, the amount of acid remaining at the end of the digestion stage is back titrated to pH 7.0 using sodium hydroxide. According to the procedure, only the total amount of base added is required to be recorded. In this study, the quantity of base added to obtain pH values of 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, and 6.0 in addition to the end point at 7.0 was recorded. The back titration curve was obtained by plotting the titration pH against the quantity of sodium hydroxide added during the titration stage, expressed as the equivalent quantity of acid remaining in moles per gram. This was done for every standard Sobek NP determination and the tests in which acid additions corresponding to two different fizz ratings were used. 3.4 NEUTRALIZATION POTENTIAL BY MODIFIED ACID BASE ACCOUNTING The neutralization potential of every sample was determined following the Modified Acid Base Accounting Procedure of Lawrence and Wang (1997). This test was originally developed (Lawrence, 1990) to reduce the overestimation of NP values obtained in the Sobek procedure. This is achieved by performing the hydrochloric acid digestion for 24 hours at a lower temperature (25-35°C), acid is added in two increments and the quantity of the acid added is controlled so that the pH of the pulp after digestion is in a specific 49 range (2.0-2.5). In addition, the end point of the back titration is 8.3 as discussed in Section 2.3.3.1. Values of NP are referred to as the Modified NP in this thesis. The modified ABA procedure used for this study is described in Appendix II. 3.5 NEUTRALIZATION POTENTIAL BY CARBONATE ANALYSIS The carbonate neutralization potential of every sample was calculated from the inorganic carbon content which was determined using a Coulimetrics Model 5030 Carbonate Carbon apparatus linked to a Coulimetrics Model 5010 C0 2 Coulometer. The method involves the addition of hydrochloric acid to a small quantity of the sample to evolve C 0 2 from contained carbonates. The carbon dioxide is absorbed quantitatively into a solution containing ethanolamine which causes a color change and a corresponding increase in the light transmittance. Hydroxyl ions are electrically generated to restore the color and the original transmittance value. The total amount of current required for the titration is integrated and the result displayed as micrograms of carbon absorbed. The CaC0 3 equivalent, and thus the neutralization potential, can then be calculated and is referred as the Carbonate NP in this thesis. 50 3.6 NEUTRALIZATION POTENTIAL BY THE LAPAKKO METHOD Lapakko (1994) carried out a comparison of prediction test methods on 10 samples and described a method by which the quantity of neutralization provided by minerals at pH's above 6 is measured. This NP is called the Lapakko NP in this thesis. In this study, 2 g of selected samples and 50 ml of water were placed in a beaker on a magnetic stirrer. Using a pH controller, 0.0 IN sulfuric acid was added at a very slow rate to achieve a stable pH of 6.0 ± 0.1. The NP (pH 6) values in units of CaC0 3 equivalent/tonne were calculated from the quantity of acid added (see Section 2.3.4.2). 3.7 OTHER ANALYSES 3.7.1 Mineralogical Analysis by X-Ray Diffraction Mineralogical analysis of a total of 29 samples was carried out in the Department of Earth Sciences, UBC and at CANMET. At UBC, analyses of 24 samples were performed using a Siemens D5000 powder X-ray diffractometer running at 40 kV and 30 mA and using Cu Koc radiation. Spectra were collected from 3 to 60° 20. At CANMET, analyses of 5 samples were achieved by using a Rigaku rotating anode X-ray powder diffractometer, with spectra collected from 5 to 90° 20, with a step size of 0.04° 20. 51 3.7.2 Analysis of Sobek Digestion Leachates Selected leachates obtained from the Sobek digestion procedure under three different fizz ratings, as described in Section 3.3.2, were analyzed for Al, Ca, Mg, Na, K and Fe by atomic absorption spectrophotometry. 52 4 . 0 R E S U L T S A N D D I S C U S S I O N S This chapter presents the results and discussions for tests on 119 samples as follows: the measurement and comparison of Sobek NP, Modified NP and Carbonate NP; the effect of different fizz ratings on the NP, NNP and NPR, endpoint pH of the digestion (EOD pH), and on the back titration curves in the Sobek test procedure. Also, the chapter includes the results and discussions of Lapakko NP determinations and mineralogical analyses by XRD for selected samples. Finally, the test results for the reference sample NBM-1 are presented. 4.1 COMPARISON OF NP BY THE SOBEK, THE MODIFIED AND THE CARBONATE METHODS Table 4-1 and Figure 4-1 show the NP values obtained by the Sobek, the Modified and the Carbonate methods. Figures 4-2, 4-3 and 4-4 show the correlation between the NP values obtained by Sobek and Modified, Sobek and Carbonate and Modified and Carbonate methods respectively. In Table 4-1, the percentage deviations in the values determined by the Modified and Carbonate procedure from the Sobek procedure value are also shown. 53 Figure 4-2 shows that, with the exception of three samples, the Modified NP values are lower than the Sobek NP values. For the three exceptions, all have very low NP values in common. Figure 4-3 shows that for all samples, the percentage deviation of Carbonate NP value from Sobek NP value are zero or negative except Sample 609-T which has very low values by any of the methods. This demonstrates that, for almost all the samples, the Carbonate NP is lower than the Sobek NP. Figure 4-4 shows the relationship between the Modified NP and Carbonate NP values. In Figure 4-4, all the test data plot close to the x=y line showing that the Modified ABA NP and Carbonate NP value have a relatively close correlation. The results demonstrate that with the exception of very few samples, the Modified NP and the Carbonate NP values are significantly lower than the corresponding Sobek NP values. This can be explained if mineralogical composition of the samples and the different test conditions are considered. As previously shown in Table 2-3, minerals can be divided into carbonates, silicates and other different groups in order of relative reactivity in acidic solution. The relative reactivity shown in Table 2-3 is at pH 5. In the more highly acidic and boiling conditions of the Sobek test, rates of reaction would be higher than those presented in the table. In such conditions, the rate of reaction of the non-carbonate minerals such as fast, intermediate, and perhaps slow weathering minerals are apparently significantly high enough to account for neutralization potential in addition 54 to the carbonate minerals. Under environmental conditions such as found in waste dumps and tailing impoundments, such extreme conditions do not occur. Although silicate dissolution might happen under lower pH conditions sometimes observed in such environments, the rate and degree of dissolution or alteration will be lower than in the Sobek test. Sherlock et al (1995) have reviewed the role of carbonates and silicates in acid rock drainage neutralization and pointed out that the reactions of silicates are slower than the more reactive carbonates. It is for this reason that the most important buffering that occurs within near surface natural waters is due to the carbonate system. The silicate reaction is limited to the rate of dissolution and alteration. The Sobek test clearly, therefore, provides an overestimation of NP availability under actual field conditions. Compared with the Sobek NP, it is concluded that the Carbonate NP and the Modified NP methods provide more realistic values. NP values obtained by the Carbonate method represent the acid consuming ability of carbonate minerals, while the Modified method accounts for NP from carbonate and the most reactive of the non-carbonate minerals which are likely to contribute to acid neutralization under environmental conditions. Figure 4-5 (Lawrence and Wang , 1997) demonstrates this more clearly. 55 RELATIVE MINERAL REACTIVITY NEUTRALIZING MINREAL F REA 'OSSIBLE EXTENT OF CTION BY NP METHOD More Reactive Less Reactive Carbonates Ca-feldspar, Olivine Pyroxenes, Amphiboles Sorosilicates, Phyllosilicates Plagioclase feldspar K-feldspar Quartz Sc 1 + Carbonate Modified )bek Figure 4-5. Mineral Reactivity in ABA NP Procedures 56 Table 4-1. Fizz Rating, the Sobek NP, Modified NP and the Carbonate NP for All Samples (in Fizz Rating column, ST: strong, M: moderate, SL: slight, N: none) Order Sample Fizz NP (kg/t) % Deviation from Sobek Rating Sobek Modified Carbonate Modified Carbonate 1 1001-T ST 158 73 65 -54 -59 2 1002-WR M 37 28 24 -24 -35 3 1003-WR N 20 21 3 5 -85 4 1004-WR M 112 51 35 -54 -69 5 101-WR N 15 5 0 -67 -100 6 102-WR M 101 30 7 -70 -93 7 103-WR M 114 22 12 -81 -89 8 104-WR SL 40 20 13 -50 -68 9 105-WR M 105 28 21 -73 -80 10 1101-WR M 67 39 40 -42 -40 11 1102-WR M 81 59 68 -27 -16 12 1103-WR ST 156 79 93 -49 -40 13 1104-WR ST 144 92 105 -36 -27 14 1201-T ST 228 109 131 -52 -43 15 1202-T ST 188 134 102 -29 -46 16 1203-T ST 185 108 78 -42 -58 17 1204-WR ST 192 121 149 -37 -22 18 1205-WR M 51 42 34 -18 -33 19 1206-WR SL 103 26 25 -75 -76 20 201-WR M 78 27 20 -65 -74 21 202-WR SL 25 15 6 -40 -76 22 203-WR N 18 11 3 -39 -83 23 204-WR N 38 34 20 -11 -47 24 205-WR M 21 10 4 -52 -81 25 206-T M 94 37 25 -61 -73 26 207-T M 52 36 22 -31 -58 27 208-T M 75 23 14 -69 -81 28 209-T M 55 24 28 -56 -49 29 210-T M 116 24 15 -79 -87 30 211-T M 92 21 8 -77 -91 31 301-T ST 135 80 74 -41 -45 32 302-T ST 113 76 72 -33 -36 33 303-T ST 146 64 61 -56 -58 34 304-T ST 163 62 57 -62 -65 35 305-WR M 89 37 33 -58 -63 36 306-WR ST 174 139 104 -20 -40 37 307-WR SL 35 20 7 -43 -80 38 308-WR ST 108 61 47 -44 -56 39 309-WR ST U l 67 64 -40 -42 40 401-T M 44 21 18 -52 -59 57 Table 4-1. Fizz Rating, the Sobek NP, Modified NP and the Carbonate NP for All Samples Order Sample Fizz NP (kg/t) % Deviation from Sobek Rating Sobek Modified Carbonate Modified Carbonate 41 402-T M 58 28 26 -40 -42 42 403-T M 51 22 21 -52 -59 43 404-WR SL 23 13 14 -52 -55 44 405-WR ST 104 52 59 -57 -59 45 406-WR ST 110 47 48 -43 -39 46 407-WR M 65 35 43 -50 -43 47 408-WR N 15 3 2 -80 -87 48 501-WR N 15 2 0 -87 -100 49 502-WR N 4 0 0 -100 -100 50 503-WR N 13 3 0 -77 -100 51 504-WR N 8 2 0 -75 -100 52 505-WR N 20 6 0 -70 -100 53 601-WR SL 12 9 8 -25 -33 54 602-WR SL 10 5 2 -50 -80 55 603-WR M 44 24 21 -45 -52 56 604-WR ST 104 57 56 -45 -46 57 605-T SL 10 8 6 -20 -40 58 606-T SL 18 15 18 -17 0 59 607-T SL 18 17 9 -6 -50 60 608-T SL 20 11 10 -45 -50 61 609-T SL 9 10 12 11 33 62 610-T SL 18 16 11 -11 -39 63 611-T SL 12 11 8 -8 -33 64 612-T SL 20 14 11 -30 -45 65 613-T M 83 29 31 -65 -63 66 701-WR N 4 -5 0 -225 -100 67 702-WR N 5 7 3 40 -40 68 703-WR N 9 -1 0 -111 -100 69 704-WR N 14 3 3 -79 -79 70 705-WR N 10 6 2 -40 -80 71 706-WR N 15 9 7 -40 -53 72 707-WR N 7 1 1 -86 -86 73 708-WR N 10 3 1 -70 -90 74 709-WR N 7 1 0 -86 -100 75 710-WR N 16 3 0 -81 -100 76 801-WR ST 124 61 53 -51 -57 77 802-WR M 97 60 47 -38 -52 78 803-WR N 6 3 0 -50 -100 79 804-WR N 10 5 1 -50 -90 80 805-WR N 15 9 4 -40 -73 81 901 -WR M 53 27 20 -49 -62 58 T a b l e 4 -1 . F i z z R a t i n g , the S o b e k N P , M o d i f i e d N P a n d the C a r b o n a t e N P f o r A l l S a m p l e s Order Sample Fizz NP (kg/t) % Deviation from Sobek Rating Sobek Modified Carbonate Modified Carbonate 82 902-WR N 22 4 0 -82 -100 83 903-WR N 12 1 0 -92 -100 84 904-WR N 20 5 1 -75 -95 85 905-WR N 32 8 3 -75 -91 86 906-WR N 29 7 0 -76 -100 87 907-WR N 14 8 2 -43 -86 88 908-WR N 20 4 1 -80 -95 89 909-WR N 29 6 1 -79 -97 90 910-WR M 120 46 40 -62 -67 91 911-WR ST 135 55 51 -59 -62 92 912-WR ST 156 77 64 -51 -59 93 913-WR ST 156 50 39 -68 -75 94 914-WR ST 149 58 40 -61 -73 95 915-WR ST 220 128 115 -42 -48 96 916-WR ST 163 69 58 -58 -64 97 917-WR M 63 25 • 16 -60 -75 98 918-WR N 24 14 8 -42 -67 99 919-WR M 96 35 30 -64 -69 100 920-WR N 22 11 3 -50 -86 101 921-WR N 22 14 9 -36 -59 102 922-WR N 30 10 1 -67 -97 103 923-WR N 37 10 0 -73 -100 104 924-WR N 24 11 2 -54 -92 105 925-WR N 13 6 0 -54 -100 106 926-WR N 10 1 0 -90 -100 107 927-WR N 18 8 0 -56 -100 108 928-WR; N 16 8 0 -50 -100 109 929-WR • N 14 5 4 -64 -71 110 930-WR N 6 1 0 -83 -100 111 CCRMP RTS-4 N 0 0 5 112 CCRMP CCU-1 N 2 0 0 -100 -100 113 CCRMP CH-3 ' ST 210 103 122 -51 -42 114 CCRMP CPB'-l M 40 28 3 -30 -93 115 CCRMP CZN-1 N 10 1 6 -90 -40 116 CCRMPKC-1A N 8 3 2 -63 -75 117 CCRMP MW-1 N 1 0 1 -100 0 118 CCRMP PC-1 N 5 0 1 -100 -80 119 CCRMP NBM-1 SL 61 30 34 -51 -44 250  T Figure 4-1. Comparison of the Sobek NP, Modified NP, and the Carbonate NP For All Samples 0 50 100 150 200 250 Sobek NP (kg/t) Figure 4-2: The Correlation of the Sobek NP and the Modified NP 61 Modified ABA NP (kg/t) Figure 4-4: The Correlation of Modified NP and Carbonate NP 63 4.2 NP BY THE LAPAKKO METHOD The procedure recommended by Lapakko (see Section 2.3.4) is based on the objective of determining NP contributed only by minerals which can neutralize acid at a pH of 6.0 and above, thereby protecting receiving waters from lower pH values. In theory this test might provide a more realistic assessment of the neutralizing capacity that can maintain pH in drainage at environmentally acceptable level. In practice, however, the measurement of NP at pH 6 is a very time consuming process. This would make the technique less desirable for NP determinations of large numbers of samples, typically, of many programs conducted in commercial laboratories. In this study, only a few selected samples were evaluated by the Lapakko method due to the time constraint. For samples which had a very low Carbonate NP value (<10 kg/tonne), sulfuric acid additions for several hours or even overnight were required to achieve a reasonable degree of equilibrium. For sample 1103-WR with the Carbonate NP of 93 kg CaC03/tonne, the time required for the titration was over 7 days. Even after these lengths of time, complete equilibrium was not achieved and tests were terminated for expediency. The NP values obtained in the Lapakko method and the comparison with the Sobek, the Modified and the Carbonate NP values were shown in Table 4-2. 64 Table 4-2. NP Values by the Sobek, Modified, Carbonate and the Lapakko Procedures NP (kg CaC03/t) Sample Sobek Modified Carbonate Lapakko 1003-WR 20 21 3 6 1103-WR 156 79 93 69 923-WR 37 10 0 4 NBM-1 61 30 34 16 Table 4-2 shows that NP values determined by the Lapakko method were considerably lower than the Sobek values. For the four samples, the Lapakko NP values were all lower than the Modified NP values. For two of the four samples tested, the Lapakko NP values were actually higher than the Carbonate NP values, although the values and their differences were very small. From this study, insufficient data are available to make general conclusions. As a research tool, however, the Lapakko method has merit by potentially providing an assessment of the NP that will be available for acid neutralization in the early stages of acid generation within wastes. 4.3 EVALUATION OF THE SOBEK TEST PROCEDURE ON THE MEASUREMENT OF NP In Section 2.3.2, the Sobek test was discussed, including a discussion of assumptions and limitations of the test. It was assumed that the test procedure is, in some ways, subjective and can lead to variations in NP values obtained for the same sample. In this study, 65 therefore, tests have been carried out to evaluate the effect of procedural variations on NP determinations. Specifically, the effect of different fizz ratings (acidity) was evaluated. Each sample was tested under a different quantity of acid corresponding to three different fizz ratings as discussed in Section 2.3.2 and as described in Section 3.3.2. For each test, the EOD pH was measured and the back-titration curve was plotted. 4.3.1 Effect of Different Fizz Rating on the Sobek NP Table 4-3 gives the fizz rating, total sulfur content, AP and the Sobek NP's, NNP's as well as NP:AP ratios at three different fizz ratings for all the samples tested. Accordingly, Figure 4-6 graphically shows the three NP's obtained for every sample. Table 4-4 and Figure 4-7 show the Sobek NP values at no, + and ++ fizz ratings for standard no-fizz samples. At acid addition corresponding to a slight-fizz rating (+), it can be noted that 5 out of 50 samples have lower NP values than obtained at the lower acid addition (no fizz rating). This would not be expected, but in all these cases, NP values were very low and the discrepancies were small and could be due to the experimental fluctuations. The rest of the samples have the % deviation in NP ranging from 0 to 300%. At the acid addition corresponding to a moderate-fizz rating (++), all the 50 samples have higher NP values compared to the NP values at no-fizz rating. The % deviation ranged from 13% to 1425%. 66 Table 4-5 and Figure 4-8 show the Sobek NP values at slight, (-) and (+) fizz ratings for standard slight-fizz samples. Table 4-6 and Figure 4-9 show the Sobek NP values at moderate, (-) and (+) fizz ratings for standard moderate-fizz samples. Table 4-7 and Figure 4-10 show the Sobek NP values at strong, (-) and (--) fizz ratings for standard strong-fizz samples. These tables and figures all show that the higher acid addition during the digestion stage, the higher NP value obtained. The results show that the NP values obtained by the Sobek procedure are strongly dependent on the quantity of acid added during the digestion stage. Since the acid added is dependent on the results of the fizz test, the role of the fizz test in the procedure is very critical. According to the writer's experience, the assignment of a fizz rating is often a subjective matter. Different technicians can give a different fizz rating to the same sample. In addition, errors in assigning fizz can easily be made if full attention is not given throughout the fizz testing procedure. Given the demands and distractions of a commercial laboratory environment, the chance of errors in assigning fizz will arise. Furthermore, it is known that in some laboratories, fizz testing is not carried out for expediency. Instead, acid additions and normality's are sometimes standardized, usually at the high end of the range corresponding to a strong fizz rating, in the belief that such practices do not effect the values of NP obtained. In addition, most laboratory reports providing NP results do not document the exact methodology followed, fizz rating, EOD pH and any variations in methodology, therefore, the application of the Sobek NP and its interpretation must be used with some caution. Whenever the Sobek NP method is 67 employed, the test procedure should be rigorously followed and fully documented. The effect of the test conditions on the resulting NP value should be considered while interpreting the data, otherwise, serious misinterpretation of the results is possible and erroneous conclusions can be drawn. Table 4-3. Fizz Ratings, AP, Sobek NPs, Net NPs and NP:AP Ratios for All Samples Order Sample Fizz Rating Sulfur(T) (%) AP (kg/t) (Std) Sobek NP (kg/t) (~,-or+) (-, + or ++) (Std) NNP (kg/t) (~,-or+) (-, + or ++) (Std) NPR (-, - or +) (-, + or ++) 1 1002-WR M 0.02 0.6 37 27 65 36 26 64 59.2 43.2 104.0 2 1003-WR N 0.66 20.6 20 30 80 -1 9 59 1.0 1.5 3.9 3 1004-WR M 4.91 153.4 112 78 156 -41 -75 3 0.7 0.5 1.0 4 101-WR N 4.55 142.2 15 21 45 -127 -121 -97 0.1 0.1 0.3 5 102-WR M 1.98 61.9 101 44 119 39 -18 57 1.6 0.7 1.9 6 103-WR M 0.54 16.9 114 35 124 97 18 107 6.8 2.1 7.3 7 104-WR S 1.38 43.1 40 22 109 -3 -21 66 0.9 0.5 2.5 8 105-WR M 0.61 19.1 105 29 153 86 10 134 5.5 1.5 8.0 9 1101-WR M 4.51 140.9 67 40 110 -74 -101 -31 0.5 0.3 0.8 10 1102-WR M 5.69 177.8 81 78 110 -97 -100 -68 0.5 0.4 0.6 11 1103-WR ST 2.84 88.8 156 90 93 67 1 4 1.8 1.0 1.0 12 1104-WR ST 1.71 53.4 144 89 106 91 36 53 2.7 1.7 2.0 13 1201-T ST 0.89 27.8 228 92 199 200 64 171 8.2 3.3 7.2 14 1203-T ST 0.67 20.9 185 95 168 164 74 147 8.8 4.5 8.0 15 1204-WR ST 0.80 25.0 192 97 133 167 72 108 7.7 3.9 5.3 16 1205-WR M 1.96 61.3 51 51 86 -10 -10 25 0.8 0.8 1.4 17 201-WR M 0.45 14.1 78 36 93 64 22 79 5.5 2.6 6.6 18 202-WR S 2.31 72.2 25 16 87 -47 -56 15 0.3 0.2 1.2 19 203-WR N 1.53 47.8 18 20 65 -30 -28 17 0.4 0.4 1.4 20 204-WR N 0.76 23.8 38 47 61 14 23 37 1.6 2.0 2.6 21 205-WR S 1.19 37.2 21 15 48 -16 -22 11 0.6 0.4 1.3 22 206-T M 1.12 35.0 94 44 104 59 9 69 2.7 1.3 3.0 23 207-T M 1.62 50.6 52 41 88 1 -10 37 1.0 0.8 1.7 24 208-T M 0.82 25.6 75 31 109 49 5 83 2.9 1.2 4.3 25 209-T M 1.66 51.9 55 36 96 3 -16 44 1.1 0.7 1.9 26 211-T M 9.09 284.1 92 28 94 -192 -256 -190 0.3 0.1 0.3 27 301-T ST 1.31 40.9 135 61 63 94 20 22 3.3 1.5 1.5 28 302-T ST 2.60 81.3 113 74 78 32 -7 -3 1.4 0.9 1.0 29 303-T ST 5.34 166.9 146 71 101 -21 -96 -66 0.9 0.4 0.6 30 304-T ST 3.44 107.5 163 84 148 56 -24 41 1.5 0.8 1.4 31 305-WR M 0.14 4.4 89 62 91 85 58 87 20.3 14.2 20.8 32 306-WR ST 3.78 118.1 174 73 171 56 -45 53 1.5 0.6 1.4 33 307-WR S 0.22 6.9 35 25 50 28 18 43 5.1 3.6 7.3 34 308-WR ST 3.47 108.4 108 55 86 0 -53 -22 1.0 0.5 0.8 35 309-WR ST 3.21 100.3 111 85 97 11 -15 -3 1.1 0.8 1.0 36 401-T M 0.07 2.2 44 28 55 42 26 53 20.1 12.8 25.1 37 402-T M 0.17 5.3 58 35 77 53 30 72 10.9 6.6 14.5 Table 4-3. Fizz Ratings, AP, Sobek NPs, Net NPs and NP: AP Ratios for All Samples Ordei Sample Fizz Rating Sulfur(T) (%) AP (kg/t) (Std) Sobek NP (kg/t) (~,-or+) (-, + or ++) (Std) NNP (~,-or+) (-, + or++) (Std) NPR (~,-or+) 1 (-, + or++) 38 403-T M 0.10 3.1 51 30 70 48 27 67 16.3 9.6 22.4 39 404-WR s 0.19 5.9 23 20 48 17 14 42 3.9 3.4 8.1 40 405-WR ST 0.30 9.4 104 79 88 95 70 79 11.1 8.4 9.4 41 406-WR ST 7.56 236.3 110 76 88 -126 -160 -148 0.5 0.3 0.4 42 407-WR M 18.90 590.6 65 43 73 -526 -548 -518 0.1 0.1 0.1 43 408-WR N 0.58 18.1 15 15 29 -3 -3 11 0.8 0.8 1.6 44 501-WR N 0.12 3.8 15 19 52 11 15 48 4.0 5.1 13.9 45 502-WR N 5.22 163.1 4 10 61 -159 -153 -102 0.0 0.1 0.4 46 503-WR N 1.50 46.9 13 19 35 -34 -28 -12 0.3 0.4 0.7 47 504-WR N 1.94 60.6 8 9 24 -53 -52 -37 0.1 0.1 0.4 48 505-WR N 6.94 216.9 20 23 53 -197 -194 -164 0.1 0.1 0.2 49 601-WR s 0.37 11.6 12 11 26 0 -1 14 1.0 1.0 2.2 50 602-WR N 1.34 41.9 10 10 35 -32 -32 -7 0.2 0.2 0.8 51 603-WR M 0.63 19.7 44 27 98 24 7 78 2.2 1.4 5.0 52 604-WR ST 0.13 4.1 104 73 89 100 69 85 25.6 18.0 21.9 53 605-T S 1.03 32.2 10 3 20 -22 -29 -12 0.3 0.1 0.6 54 606-T S 1.81 56.6 18 15 21 -39 -42 -36 0.3 0.3 0.4 55 607-T S 0.54 16.9 18 14 66 1 -3 49 1.1 0.8 3.9 56 608-T s 1.06 33.1 20 17 31 -13 -16 -2 0.6 0.5 0.9 57 609-T s 1.12 35.0 9 6 19 -26 -29 -16 0.3 0.2 0.5 58 610-T s 0.78 24.4 18 17 61 -6 -7 37 0.7 0.7 2.5 59 611-T s 0.59 18.4 12 11 36 -6 -7 18 0.7 0.6 2.0 60 612-T s 0.59 18.4 20 18 49 2 0 31 1.1 1.0 2.7 61 613-T M 2.10 65.6 83 28 103 17 -38 37 1.3 0.4 1.6 62 701-WR N 1.49 46.6 4 9 17 -43 -38 -30 0.1 0.2 0.4 63 702-WR N 3.32 103.8 5 9 52 -99 -95 -52 0.0 0.1 0.5 64 703-WR N 0.87 27.2 9 11 46 -18 -16 19 0.3 0.4 1.7 65 704-WR N 0.74 23.1 14 15 25 -9 -8 2 0.6 0.6 1.1 66 705-WR N 0.51 15.9 10 15 39 -6 -1 23 0.6 0.9 2.4 67 706-WR N 0.85 26.6 15 17 31 -12 -10 4 0.6 0.6 1.2 68 707-WR N 0.63 19.7 7 9 20 -13 -11 0 0.4 0.5 1.0 69 708-WR N 0.65 20.3 10 9 37 -10 -11 17 0.5 0.4 1.8 70 709-WR N 0.38 11.9 7 7 31 -5 -5 19 0.6 0.6 2.6 71 710-WR N 3.61 112.8 16 19 37 -97 -94 -76 0.1 0.2 0.3 72 801-WR ST 3.84 120.0 124 83 102 4 -37 -18 1.0 0.7 0.9 73 802-WR M 7.50 234.4 97 80 138 -137 -154 -96 0.4 0.3 0.6 74 803-WR N 6.74 210.6 6 5 34 -205 -206 -177 0.0 0.0 0.2 75 804-WR N 7.94 248.1 10 14 39 -238 -234 -209 0.0 0.1 0.2 76 805-WR N 6.45 201.6 15 20 75 -187 -182 -127 0.1 0.1 0.4 77 901-WR M 2.84 88.8 53 74 115 -36 -15 26 0.6 0.8 1.3 Table 4-3 Fizz Ratings, AP, Sobek NPs, Net NPs and NP:AP Ratios for All Samples Order Sample Fizz Rating SuIfur(T) (%) AP (kg/t) (Std) Sobek NP (kg/t) (-,-or+) (-, + or++) (Std) NNP (kg/t) (~,-or+) (-, + or++) (Std) NPR (-, - or +) (-, + or++) 78 902-WR N 2.15 67.2 22 21 39 -45 -46 -28 0.3 0.3 0.6 79 903-WR N 4.58 143.1 12 15 34 -131 -128 -109 0.1 0.1 0.2 80 904-WR N 3.46 108.1 20 21 31 -88 -87 -77 0.2 0.2 0.3 81 905-WR N 2.74 85.6 32 36 36 -54 -50 -50 0.4 0.4 0.4 82 906-WR N 1.40 43.8 29 32 36 -15 -12 -8 0.7 0.7 0.8 83 907-WR N 1.43 44.7 14 23 27 -31 -22 -18 0.3 0.5 0.6 84 908-WR N 3.45 107.8 20 18 39 -88 -90 -69 0.2 0.2 0.4 85 909-WR N 3.38 105.6 29 32 35 -77 -74 -71 0.3 0.3 0.3 86 910-WR M 2.25 70.3 120 72 130 50 2 60 1.7 1.0 1.8 87 911-WR ST 1.80 56.3 135 81 106 79 25 50 2.4 1.4 1.9 88 912-WR ST 2.74 85.6 156 89 132 70 3 . 46 1.8 1.0 1.5 89 913-WR ST 2.12 66.3 156 77 118 90 11 52 2.4 1.2 1.8 90 914-WR ST 1.33 41.6 149 80 111 107 38 69 3.6 1.9 2.7 91 916-WR ST 1.15 35.9 163 84 109 127 48 73 4.5 2.3 3.0 92 917-WR M 1.31 40.9 63 44 . 70 22 3 29 1.5 1.1 1.7 93 918-WR N 1.22 38.1 24 33 67 -14 -5 29 0.6 0.9 1.8 94 919-WR M 2.85 89.1 96 56 115 7 -33 26 1.1 0.6 1.3 95 920-WR N 1.46 45.6 22 34 71 -24 -12 25 0.5 0.7 1.6 96 921-WR N 3.57 111.6 22 31 56 -90 -81 -56 0.2 0.3 0.5 97 922-WR N 0.81 25.3 30 43 68 5 18 43 1.2 1.7 2.7 98 923-WR N 1.90 59.4 37 44 76 ' -22 -15 17 0.6 0.7 1.3 99 924-WR N 1.64 51.3 24 37 50 -27 -14 -1 0.5 0.7 1.0 100 925-WR N 3.08 96.3 13 21 53 -83 -75 -43 0.1 0.2 0.6 101 926-WR N 1.62 50.6 10 16 34 -41 -35 -17 0.2 0.3 0.7 102 927-WR N 1.06 33.1 18 27 49 -15 -6 16 0.5 0.8 1.5 103 928-WR N 1.66 51.9 16 20 55 -36 -32 3 0.3 0.4 1.1 104 929-WR N 3.24 101.3 14 18 47 -87 -83 -54 0.1 0.2 0.5 105 930-WR N 1.53 47.8 6 10 27 -42 -38 -21 0.1 0.2 0.6 106 CCRMP RTS-4 N 35.90 1121.9 0 3 6 -1122 -1119 -1116 0.0 0.0 0.0 107 CCRMP CCU-18 N 34.80 1087.5 2 3 18 -1086 -1085 -1070 0.0 0.0 0.0 108 CCRMP CH-3 ST 2.82 88.1 210 90 180 122 2 92 2.4 1.0 2.0 109 CCRMP CPB-1 M 17.80 556.3 40 11 40 -516 -545 -516 0.1 0.0 0.1 110 CCRMP CZN-1 N 30.20 943.8 10 11 28 -934 -933 -916 0.0 0.0 0.0 111 CCRMP KC-1A N 27.50 859.4 8 7 16 -851 -852 -843 0.0 0.0 0.0 112 CCRMP MW-1 N 0.01 0.3 1 4 11 1 4 11 3.2 12.8 35.2 113 CCRMP PC-1 N 6.96 217.5 5 5 23 -213 -213 -195 0.0 0.0 0.1 114 CCRMP NBM-1 S 0.30 9.4 61 41 95 52 32 86 6.5 4.4 10.1 © 250 200 --150 1 100 -50 -4 1  • • (Std) • (-, - or +) (-, + or ++) II I II II II I I I I M I M 1 II I II I I I II I II I II I I I I I II II I II I I I I I I M I II I I I II 11111111111111111111 ii i ii 111 ii 11 ii 111 ii tn i ii 1*111 Sample Order Figure 4-6, NP Values Obtained by the Sobek Procedure at different Fizz Ratings for All Samples Table 4-4. NPs by the Sobek Procedure for No Fizz Samples Figure 4-7. NPs by the Sobek Procedure for No Fizz Samples NP(kg/t) % Deviation from Std Order Sample No Fizz Slight Strong Slight Strong 1 1003-WR 20 30 80 50 300 2 101-WR 15 21 45 40 200 3 203-WR 18 20 65 11 261 4 204-WR 38 47 61 24 61 5 408-WR 15 15 29 0 93 6 501-WR 15 19 52 27 247 7 502-WR 4 10 61 150 1425 S 503-WR 13 19 35 46 169 9 504-WR 8 9 24 13 200 10 505-WR 20 23 53 15 165 11 602-WR 10 10 35 0 250 12 701-WR 4 9 17 125 325 13 702-WR 5 9 52 80 940 14 703-WR 9 11 46 22 411 15 704-WR 14 15 25 7 79 16 705-WR 10 15 39 50 290 17 706-WR 15 17 31 13 107 18 707-WR 7 9 20 29 186 19 708-WR 10 9 37 -10 270 20 709-WR 7 7 31 0 343 21 710-WR 16 19 37 19 131 :: 803-WR 6 5 34 -17 467 23 804-WR 10 14 39 40 290 24 805-WR 15 20 75 33 400 25 902-WR 22 21 39 -5 77 26 903-WR 12 15 34 25 183 27 904-WR 20 21 31 5 55 28 905-WR 32 36 36 13 13 29 906-WR 29 32 36 10 24 30 907-WR 14 23 27 64 93 31 908-WR 20 18 39 -10 95 32 909-WR 29 32 35 10 21 33 918-WR 24 33 67 38 179 34 920-WR 22 34 71 55 223 35 921-WR 22 31 56 41 155 36 922-WR 30 43 68 43 127 37 923-WR 37 44 76 19 105 38 924-WR 24 37 50 54 108 39 925-WR 13 21 53 62 308 40 926-WR 10 16 34 60 240 41 927-WR 18 27 49 50 172 42 928-WR 16 20 55 25 244 43 929-WR 14 18 47 29 236 44 930-WR 6 10 27 67 350 45 CCRMP RTS-4 0 3 6 46 CCRMP CCU-IB 2 3 18 50 800 47 CCRMP CZN-1 10 11 28 10 180 48 CCRMPKC-1A 8 7 16 -13 100 49 CCRMP MW-1 1 4 11 300 1000 50 CCRMP PC-1 5 5 23 0 360 • No Fizz • Slight Strong 0 I I I 1 I I I I I I I I Sample Order II i M m i I o w ^ 3 Table 4-5: NPs by the Sobek Procedure for Slight Fizz Samples Figure 4-8. NPs by the Sobek Procedure for Slight Fizz Samples NP (kg/t) % Deviation from Std Order Sample Std + + 1 104-WR 40 22 109 -45 173 2 202-WR 25 16 87 -36 248 3 205-WR 21 15 48 -29 129 4 307-WR 35 25 50 -29 43 5 404-WR 23 20 48 -13 109 6 601-WR 12 11 26 -8 117 7 605-T 10 3 20 -70 100 8 606-T 18 15 21 -17 17 9 607-T 18 14 66 -22 267 10 608-T 20 17 31 -15 55 11 609-T 9 6 19 -33 111 12 610-T 18 17 61 -6 239 13 611-T 12 11 36 -8 200 14 612-T 20 18 49 -10 145 15 CCRMP NBM-1 61 41 95 -33 56 120 -r 100 + SO S-Z 60 + 40 20 -• « Std H h H 1 1 +-Sample Order (n m *r w> 1^ Table 4-6. NPs by the Sobek Procedure for Moderate Fizz Samples NP(kg/t) % Deviation from Std Order Sample Std -+ . + 1 1002-WR 37 27 65 -27 76 2 1004-WR 112 78 156 -30 39 3 102-WR 101 44 119 -56 18 4 103-WR 114 35 124 -69 9 5 105-WR 105 29 153 -72 46 6 1101-WR 67 40 no -40 64 7 1102-WR 81 78 110 -4 36 8 1205-WR 51 51 86 0 69 9 201-WR 78 36 93 -54 19 10 206-T 94 44 104 -53 11 11 207-T 52 41 88 -21 69 12 208-T 75 31 109 -59 45 13 209-T 55 36 96 -35 75 14 211-T 92 28 94 -70 2 15 305-WR 89 62 91 -30 2 16 401-T 44 28 55 -36 25 17 402-T 58 35 77 -40 33 18 403-T 51 30 70 -41 37 19 407-WR 65 43 73 -34 12 20 603-WR 44 27 98 -39 123 21 613-T 83 28 103 -66 24 22 802-WR 97 80 138 -18 42 23 901-WR 74 53 115 -28 55 24 910-WR 120 72 130 -40 8 25 917-WR 63 44 70 -30 11 26 919-WR 96 56 115 -42 20 27 CCRMP CPB-1 40 11 40 -73 0 Figure 4-9. NPs by the Sobek Procedure for Moderate Fizz Samples 160 KmiJ:^ A A 140 •• A 120 < k f A A . . A. :: 100 ::.<»'••'. A 140 •• A 120 < k f A A . . A. :: 100 ::.<»'••'. • : :•: .:: '' :: ; 140 •• A 120 < k f A A . . A. :: 100 ::.<»'••'. ;: ;:;S:;f:':JSPPS|f| :; 1A:ii g: A i 1 : A :: t , • STD Z 80 .. I » ^<;m • -C c .. j a AH :=S:E 8 -Z 80 .. I » ^<;m • -C c T A 1 A + 60 -iiiiii 60 -iiiiii •£<m i: . a a " j: i :  * :: s a 40 ' ijr-p- y'WWM lils " • i 8 8 B " « 20 •-to" B i a v;-':;[ B — m v-i ON — Sample lllllflllllHiS r:'P:r;::':::':  > i ! •i:--f::'r'T-:f:j »/N Ov m v-> r~ Order Table 4-7. NPs by the Sobek Procedure for Strong Fizz Samples NP(kg/t) % Deviation from Std Order Sample Std — -— 1 1103-WR 156 90 93 -42 -40 2 1104-WR 144 89 106 -38 -26 3 1201-T 228 92 199 -60 -13 4 1203-T 185 95 168 -49 -9 5 1204-WR 192 97 133 -49 -31 6 301-T 135 61 63 -55 -53 7 302-T 113 74 78 -35 -31 8 303-T 146 71 101 -51 -31 9 304-T 163 84 148 -48 -9 10 306-WR 174 73 171 -58 -2 11 308-WR 108 55 86 -49 -20 12 309-WR 111 85 97 -23 -13 13 405-WR 104 79 88 -24 -15 14 406-WR 110 76 88 -31 -20 15 604-WR 104 73 89 -30 -14 16 801-WR 124 83 102 -33 -18 17 911-WR 135 81 106 -40 -21 IS 912-WR 156 89 132 -43 -15 19 913-WR 156 77 118 -51 -24 20 914-WR 149 80 111 -46 -26 21 916-WR 163 84 109 -48 -33 22 CCRMP CH-3 210 90 180 -57 -14 Figure 4-10. NPs by the Sobek Procedure for Strong Fizz Samples 250 i t 200 • C 150 -. f :: 1 *K-::: • V j 1 4 * l!llllllllillllll 11 il;f 1:11 1 t 1 • STD obek NP ii'I, .. ::: :: ! :  :\ 1 • t B -A-ii'I, .. ::: :: ! :  :\ 1 • • • , 4 A :: .« , .: :•: il-/•• :.: T:::; ON IOO -0 «• A J • * *  a • 50 -0 0 -0 -1 1 — m r- o\ — Sampl faspyspaj vf:^w:^^m^fm: m >n p. ON £j e Order -J 76 4.3.2 Effect of Different Fizz Rating on Endpoint pH of Digestion Using Sobek The results of the endpoint pH values are shown graphically for each fizz category in Figure 4-11. The range of final pH values for tests were shown in Table 4-8. Table 4-8. The Range of Final pH Values for the Sobek Standard Tests Fizz Category pH Range Typical End pH No fizz 1.60-5.20 2.0-2.5 Slight fizz 0.76-2.10 1.5 Moderate fizz 0.77-1.83 1.0 Strong fizz 0.35-1.07 0.8 The end pH value for each standard fizz classification are presented in Table 4-9, Table 4-10, Table 4-11 and Table 4-12 while Figure 4-12, Figure 4-13, Figure 4-14 and Figure 4-15 correspondingly show the data graphically. The above results show that the endpoint pH values are highest for tests on no-fizz samples and lowest for the strong-fizz samples. Clearly, for all the samples, the more acid added during the digestion stage, the lower pH value will get after the digestion. For example, using the 50 samples classified as standard no-fizz samples (Table 4-9 and Figure 4-12), the EOD pH can be seen to vary from 1.60 to 5.20 at the standard no fizz rating, from 1.30 to 3.50 at + fizz rating and 0.97 to 1.45 at ++ fizz rating. This is to be expected since endpoint pH values after digestion usually give a good indication of the 77 degree of excess acidity added in the test. In the Sobek test, the amount of acid added during digestion is lowest at the no-fizz rating and highest at the strong-fizz rating in order to meet the requirements for higher acid additions for higher fizz rating samples. For example, at the strong fizz rating, the quantity of acid added is stoichiometrically equivalent to a NP of 1,000 kg CaC03/tonne. Therefore, overestimation of NP values is more likely with the higher fizz samples, since a strong fizz rating can be assigned for samples with NP contents significantly lower than the maximum value. 6.0 5.0 § • 1 •a ? 3.0 m h 6 • • • • • • • • * • 5 2.0 t * w • • % * • • % 1.0 K Xxxx*  xx 0.0 xxxxx • No-fizz I Slight-fizz Moderate-fizz X Strong-fizz II I I II II I I I 1 1 I I I 1 I I I 1 1 I I I I 1 1 I I 1 1 1 I I I 1 I I 1 1 1 I I I 1 I 1 i/~>ONr<->r~^-ir>o>ic«">t"~-'— m a\ Sample Number Figure 4-11 pH after Digestion from Sobek Test Table 4-9. pH after Digestion by the Sobek for No Fizz Samples Figure 4-12. pH after Digestion by the Sobek for No Fizz Samples pH After Digestion Order Sample Std + +-1 1003-WR 4.28 1.37 1.07 2 101-WR 2.80 1.80 1.24 3 203-WR 2.10 1.60 0.97 4 204-WR 3.18 2.34 1.26 5 408-WR 2.10 1.50 1.20 6 501-WR 2.10 1.60 1.23 7 502-WR 2.10 1.70 1.22 8 503-WR 2.32 1.70 1.24 9 504-WR 2.00 1.60 1.23 10 505-WR 2.80 2.20 1.25 11 602-WR 2.30 1.76 1.22 12 701-WR 2.05 1.60 1.21 13 702-WR 3.50 1.80 1.16 14 703-WR 2.10 1.60 1.20 15 704-WR 2.20 1.60 1.22 16 705-WR 2.15 1.60 1.22 17 706-WR 2.10 1.60 1.20 18 707-WR 2.00 1.60 1.25 19 708-WR 2.05 1.60 1.24 20 709-WR 2.05 1.60 1.21 21 710-WR 2.15 1.60 1.21 22 803-WR 1.60 1.30 1.23 23 804-WR 2.10 1.60 1.34 24 805-WR 1.90 1.70 1.24 25 902-WR 2.40 1.70 1.40 26 903-WR 2.20 1.65 1.46 27 904-WR 2.50 1.70 1.39 28 905-WR 3.10 1.85 1.34 29 906-WR 2.90 1.80 1.37 30 907-WR 3.10 1.95 1.44 31 908-WR 2.40 1.70 1.42 32 909-WR 3.10 1.80 1.38 33 918-WR 2.60 1.90 1.51 34 920-WR 2.60 1.90 1.47 35 921-WR 2.60 1.90 1.22 36 922-WR 3.30 2.15 1.32 37 923-WR 5.20 2.20 1.28 38 924-WR 2.50 1.95 1.23 39 925-WR 2.30 1.70 1.22 40 926-WR 2.40 1.75 1.17 41 927-WR 2.60 1.90 1.22 42 928-WR 2.30 1.80 1.26 43 929-WR 2.30 1.80 1.20 44 930-WR 2.05 1.60 1.17 45 CCRMP RTS-4 3.82 3.50 1.45 46 CCRMP CCU-IB 2.21 1.75 1.03 47 CCRMP CZN-1 3.95 1.98 1.23 48 CCRMP KC-1A 2.30 1.88 1.20 49 CCRMP MW-1 2.18 1.80 1.16 50 CCRMP PC-1 1.98 1.60 1.15 6.00 4.00 1 Sample Order 3 Table 4-10. pH after Digestion by the Sobek for Slight Fizz Samples Figure 4-13. pH after Digestion by the Sobek for Slight Fizz Samples pH After Digestion Order Sample Std _ + 1 104-WR 2.10 2.50 1.17 2 202-WR 1.50 2.05 0.97 3 205-WR 1.30 1.90 0.94 4 307-WR 1.30 1.90 0.94 5 404-WR 1.60 2.45 0.68 6 601-WR 1.30 1.70 0.72 7 605-T 1.43 1.73 0.86 8 606-T 1.33 1.80 0.90 9 607-T 1.40 1.80 0.92 10 608-T 1.39 2.05 1.02 11 609-T 1.38 2.45 0.86 12 610-T 1.37 1.80 1.02 13 611-T 1.30 1.70 0.64 14 612-T 1.30 2.10 0.90 15 CCRMP NBM-1 2.40 2.35 0.70 2.50 T 2.00 J 1.50 1.00 0.50 0.00 H 1 1 1 1 1 h • Std Sample Order 5 Table 4-11. pH after Digestion by the Sobek for Moderate Fizz Samples Figure 4-14. pH after Digestion by the Sobek for Moderate Fizz Samples pH After Digestion Order Sample Std -+ 1 1002-WR 0.80 1.40 0.60 2 1004-WR 1.30 2.30 1.02 3 102-WR 0.90 2.10 0.66 4 103-WR 1.14 2.10 0.98 5 105-WR 0.98 2.10 0.06 6 1101-WR 0.90 1.60 0.60 7 1102-WR 1.29 2.17 0.99 g 1205-WR 0.77 1.80 0.39 9 201-WR 0.96 1.40 0.46 10 206-T 1.03 2.29 0.45 11 207-T 1.13 1.55 0.57 12 208-T 1.33 1.50 0.56 13 209-T 0.87 1.40 0.52 14 211-T 1.03 0.90 0.76 15 305-WR 1.24 2.00 0.67 16 401-T 0.90 1.50 0.38 17 402-T 0.85 1.60 0.38 18 403-T 0.86 1.60 0.42 19 407-WR 0.72 1.80 0.30 20 603-WR 0.64 1.30 0.34 21 613-T 0.64 1.30 0.35 22 802-WR 0.90 2.22 0.70 23 901-WR 0.90 2.30 0.60 24 910-WR 0.82 2.90 0.60 25 917-WR 1.20 2.00 0.90 26 919-WR 0.9 2.2 0.5 27 CCRMP CPB-1 1.25 1.80 1.00 3.00 2.50 - i 2.00 1.50 --1.00 -0.50 • Std • *< 0.00 -I 1 1 1 1 1 1 I I 1 ( 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 r-Sample Order Table 4-12. pH after Digestion by the Sobek for Strong Fizz Samples Figure 4-15. pH after Digestion by the Sobek Procedure for Strong Fizz Samples pH After Digestion Order Sample Std 1 1103-WR 1.07 4.28 1.37 2 1104-WR 1.02 4.70 1.35 3 1201-T 0.90 5.10 1.40 4 1203-T 0.52 5.04 0.93 5 1204-WR 0.45 4.90 0.85 6 301-T 0.96 3.36 1.35 7 302-T 0.89 3.45 1.38 8 303-T 0.90 4.74 1.53 9 304-T 0.98 3.48 1.44 10 306-WR 0.81 2.40 1.46 11 308-WR 1.05 3.29 1.22 12 309-WR 0.46 3.10 1.13 13 405-WR 0.37 2.22 0.69 14 406-WR 0.35 2.17 0.71 15 604-WR 0.84 2.22 1.21 16 801-WR 1.00 2.50 1.31 17 911-WR 0.60 2.75 0.90 18 912-WR 0.60 2.75 0.90 19 913-WR 0.50 2.95 0.92 20 914-WR 0.60 2.48 0.90 21 916-WR 0.50 3.07 0.90 22 CCRMP CH-3 0.80 4.96 1.40 6.00 5.00 4.00 --1 ? 3.00 2.00 --1.00 HI 11 1 uiu* 0.00 -I 1 1 h H 1 h H 1 H • Std Sample Order 83 4.3.3 Effect of a Different Fizz Rating on Cation Dissolution The analyses of digestion leachates for 7 samples, given in Table 4-13, Figures 4-16 and 4-17, show that for all samples, the amount of aluminum, magnesium, sodium, potassium and iron leached during sample digestion, increased with increasing acid addition in the digestion (increasing fizz rating). However, in all cases except sample 305-WR, the amount of calcium leached did not increase significantly with increasing acid addition. This indicates that, with the exception of sample 305-WR, the lowest acid addition was sufficient to react all of the calcium-containing minerals in the samples. For sample 305-WR, when the acid addition was increased from an amount corresponding to slight fizz, to moderate fizz and then to strong fizz, the calcium increased from 64.9mg/L, to 88.6mg/L and 96.8mg/L respectively (see Figure 4-16 ). It is postulated that, for this sample, there must be some calcium silicates in the sample which dissolved and contributed to the NP value when more acid was added. The mineralogical analysis by XRD (Table 4-15) shows that the minerals identified in sample 305-WR are quartz, plagioclase, muscovite, chlorite, amphibole, pyrite and chalcopyrite. It is assumed that increased dissolution of some calcium-containing amphiboles such as tremolite-actinolite or hornblende in the sample are accounting for the increase in NP value with increasing acid addition. Inspection of Figures 4-16 and 4-17, show clearly that the increasing amounts of the leached silicate mineral cations, Al, Fe, K, Mg, Ca and Na are directly related to an increase in the NP values. This confirms that the increasing silicate dissolution with increasing acid addition which corresponds to the use of a higher fizz rating. 84 Table 4-13: Analysis of Digestion Leachates for Sobek Tests Sample NP Method Fizz Rating NP(kg/t) Leachate Analysis (mg/L) Following Sobek Procedure Al Ca Mg Na K Fe 101-WR Sobek (standard) None 15 7.6 8.6 5.7 0.29 7.5 18.2 Sobek (+)• Slight 21 15.4 9.2 11.5 0.32 12.9 30.0 Sobek (++) Moderate 45 42.3 9.8 32.5 0.35 30.7 65.3 Modified ABA 5 Carbonate 0 105-WR Sobek (-) Slight 29 13.7 38.1 12.4 0.91 13.1 27.8 Sobek (standard) Moderate 105 67.6 38.1 58.2 1.14 49.8 124.4 Sobek (+) Strong 153 88.9 38.2 77.4 1.28 66.5 151.1 Modified ABA 28 Carbonate 21 201-WR Sobek (-) Slight 35 14.2 40.1 12.0 0.45 1.5 26.7 Sobek (standard) Moderate 78 50.0 48.4 37.1 0.84 1.8 87.0 Sobek (+) Strong 93 51.0 50.2 38.4 0.99 2.0 87.4 Modified ABA 27 Carbonate 20 305-WR Sobek (-) Slight 62 14.0 64.9 9.3 0.34 0.9 24.8 Sobek (standard) Moderate 89 49.1 88.6 30.4 0.68 1.2 76.3 Sobek (+) Strong 91 59.5 96.8 33.9 0.80 1.4 84.3 Modified ABA 37 Carbonate 33 404-WR Sobek (-) None 20 5.3 29.1 2.1 0.68 4.5 24.9 Sobek (standard) Slight 23 11.8 29.7 2.9 0.81 5.3 38.8 Sobek (+) Moderate 48 20.3 29.5 4.3 0.98 7.1 45.7 Modified ABA 13 Carbonate 14 1003-WR Sobek (standard) None 20 8.5 17.2 7.3 0.21 13.0 10.4 Sobek (+) Slight 30 17.0 18.4 15.5 0.31 21.8 20.4 Sobek (++) Moderate 80 18.6 20.8 50.6 0.38 31.6 38.6 Modified ABA 21 Carbonate 3 1102-WR Sobek (-) Slight 78 2.3 77.0 9.2 0.05 2.7 16.2 Sobek (standard) Moderate 81 4.5 77.1 9.4 0.09 4.3 17.0 Sobek (+) Strong 110 6.1 78.3 9.8 0.09 4.7 17.7 Modified ABA 59 Carbonate 68 Sample 305-WR 62 89 91 NP (kg/t) Figure 4-16. Analysis of Sobek Digestion Leachates for Sample 305-WR at Different Fizz Ratings Figure 4-17. Analysis of Sobek Digestion Leachates for Testing of Selected Samples at Different Fizz Ratings 87 4.3.4 Effect of NP Determination method on Net NP and NP: AP Ratio It has been shown from the previous results and discussions, that the impact on NP values by different assessment of the fizz rating is significant. The implications of these results on Net NP and NP: AP ratio values, which are used to interpret static test data, classify samples, and for waste management planning, will be discussed in this section. Table 4-2 gives fizz ratings, total sulfur content, AP, Sobek NP, NNP and NP:AP ratio for all sample tested using the Sobek procedure. Tables 4-14(a), 4-14(b), 4-14(c), and 4-14(d) show the interpretation of the Sobek results with different fizz ratings using both NNP and NPR criteria. Tables 4-14(a), 4-14(b), 4-14(c) and 4-14(d) show that, for each fizz category, as acid additions are increased, more samples can be classified as "safe". For example, for moderate fizz samples and using the Net NP criteria, at the "-" fizz rating 22% are safe, 37% are unsafe, at the actual moderate-fizz rating, 52% are safe, 26% are unsafe, and at the "+" fizz rating, 74% are safe and only 22% are unsafe. For the same samples and using the NP:AP ratio criteria (Price 1997), at the "-" fizz rating 19% are safe, 56% are unsafe, at the actual moderate-fizz rating, 30% are safe, 37% are unsafe, and at the "+" fizz rating, 37% are safe, 26% are unsafe. The results show that the NP, NNP and NPR variations at different fizz ratings are very significant. Evidently, if the NP value is significantly underestimated or overestimated, 88 the NNP and NPR value might change correspondingly to a large extent. As a result, if a sample is classified based on the overestimated NP value, some unsafe samples would be classified as safe, and mining company might not be required to do further tests on these samples. The waste rock and tailings may, therefore, be disposed in some situation which might generate ARD some time in the future and have a detrimental impact on the environment. On the other hand, if a sample classification based on the underestimated NP value, some safe samples would be classified as unsafe samples. In this case, the mining company will usually be required to do extra study on the sample or take unnecessary control measures to prevent ARD. This might give more financial burdens to the mining companies, and in extreme cases may make the project unfeasible. For this study, the AP value of each sample was determined only by measuring total sulfur. The comparison of NNP and NPR from the Sobek NP, the Modified NP, the Carbonate NP and Lapakko NP were, therefore, not carried out. However, from the preceding results, NP values depend significantly on the test method used or on procedural variations within a specific method, the values of Net NP and NP: AP ratio will vary accordingly. The significance of the variations is particularly apparent if the regulatory guidelines for different jurisdictions are considered. Clearly, if the NP value is significantly overestimated, the Net NP value might change from an acid consuming value to an acid producing value if a lower, more realistic NP value is used. Similarly, a NP:AP ratio exceeding a particular guideline value (safe) might change to one less than the guideline value (sample requires further testing or ARD control measures are required) when using a lower NP value. Table 4-14(a). Interpretation of Sobek Results For No-Fizz Samples by Net NP and NP:AP Ratio Criterias For Net NP Criteria: if Net NP >=+20, non-acid generating if -20 < Net NP < +20, uncertain if Net NP <= -20, acid generating No-Fizz + (Slight-Fizz) ++ (Moderate-Fizz) Criteria Number of Sample % Number of Sample % Number of Sample % "NetNP>=+20" 0 0 1 2 7 14 "-20<NetNP<20" 34 68 31 62 18 36 "NetNP<=-20" 16 32 18 36 25 50 Total 50 100 50 100 50 100 For NP:AP Ratio Criteria: if NPR <= 1, likely ARD generating if 1 < NPR < 4, uncertain if NPR >= 4, none ARD generating No-Fizz + (Slight-Fizz) ++ (Moderate-Fizz) Criteria Number of Sample % Number of Sample % Number of Sample % NPR>=4 0 0 2 4 2 4 1 <NPR<4 4 8 3 6 16 32 NPR<= 1 46 92 45 90 32 64 Total 50 100 50 100 50 100 Table 4-14(b). Interpretation of Sobek Results For Slight-Fizz Samples by Net NP and NP:AP Ratio Criterias For Net NP Criteria: if Net NP >=+20, non-acid generating if -20 < Net NP < +20, uncertain if Net NP <= -20, acid generating Slight-Fizz - (No-Fizz) + (Moderate-Fizz) Criteria Number of Sample % Number of Sample % Number of Sample % "NetNP>=+20" 2 13 1 7 7 47 "-20<NetNP<20" 9 60 8 53 7 47 "NetNP<=-20" 4 27 6 40 1 7 Total 15 100 15 100 15 100 For NP:AP Ratio Criteria: if NPR <= 1, likely ARD generating if 1 < NPR < 4, uncertain if NPR >= 4, none ARD generating Slight-Fizz - (No-Fizz) + (Moderate-Fizz) Criteria Number of Sample % Number of Sample % Number of Sample % NPR>=4 2 13 1 7 3 20 1 <NPR<4 3 ""20 2 13 8 53 NPR<= 1 10 67 12 80 4 27 Total 15 100 15 100 15 100 Table 4-14(c). Interpretation of Sobek Results For Moderate-Fizz Samples by Net NP and NP:AP Ratio Criterias For Net NP Criteria: if Net NP >+20, non-acid generating if-20 <= Net NP <= +20, uncertain if Net NP < -20, acid generating Moderate-Fizz - (Slight-Fizz) + (Strong-Fizz) Criteria Number of Sample % Number of Sample % Number of Sample % "NetNP>=+20" 14 52 6 22 20 74 "-20<NetNP<20" 6 22 11 41 1 4 "NetNP<=-20" 7 26 10 37 6 22 Total 27 100 27 100 27 100 For NP:AP Ratio Criteria: if NPR <= 1, likely ARD generating if 1 < NPR < 4, uncertain if NPR >= 4, none ARD generating Moderate-Fizz - (Slight-Fizz) + (Strong-Fizz) Criteria Number of Sample % Number of Sample % Number of Sample % NPR>=4 8 30 5 19 10 37 1 <NPR<4 9 33 7 26 10 37 NPR<= 1 10 37 15 56 7 26 Total 27 100 27 100 27 100 Table 4-14(d). Interpretation of Sobek Results For Strong-Fizz Rating by Net NP and NP:AP Ratio Criterias For Net NP Criteria: if Net NP >=+20, non-acid generating if -20 < Net NP < +20, uncertain if Net NP <= -20, acid generating Strong-Fizz - (Slight-Fizz) - (Moderate-Fizz) Criteria Number of Sample % Number of Sample % Number of Sample % "NetNP>=+20" 17 77 9 41 7 47 "-20<NetNP<20" 3 14 7 32 7 47 "NetNP<=-20" 2 9 6 27 1 7 Total 22 100 22 100 15 100 For NP:AP Ratio Criteria: if NPR <= 1, likely ARD generating if 1 < NPR < 4, uncertain if NPR >= 4, none ARD generating Strong-Fizz - (Slight-Fizz) - (Moderate-Fizz) Criteria Number of Sample % Number of Sample % Number of Sample % NPR>=4 6 27 3 14 5 23 1 <NPR<4 12 55 8 36 10 45 NPR <= 1 4 18 11 50 7 32 Total 22 100 22 100 22 100 Table 4-15(a) Minerals identified by x-ray diffraction in selected samples (UBC) Sample Quartz K-feldspar Plagioclase Muscovite Biotite Chlorite Amphibole Calcite Dolomite Pvrite Chalcopyrite Sphalerite Pvrrhotite Gypsum iron Oxide Clay 1001-WR + + + • + + + + 1003-WR + + + + + + 10-WR + + + + + + + 105-WR + + + + 1102-WR + + + 1201-WR + + + + + 1205-WR + + + + + 201-WR + + + + + + 209-T + + + + + 303-T + + + + + + 305-WR + + + + + + + 402-T + + + 404-WR + + + + 407-WR + + + + + 502-WR + + + + + + + 604-WR + + + + + 610-T + + + + + + + 703-WR + + + + 801-WR + + + + + + 805-WR + + + + 911-WR + + + + + + 915-WR + + + + + 917-WR + + + + 923-WR + + + + + Table 4-15 (b) Minerals identified by x-ray diffraction in selected samples (CANMET) Sample Quartz K-feldspar Plagioclase Muscovite Biotite Chlorite Amphibole Calcite Dolomite Pyrite Chalcopyrite Sphalerite Pyrrhotite Gypsum iron Oxide Clay 103-WR + + + + + 211-T + + + + + + + 310-T + + + + + + + 906-WR + + + + + 104-WR + + + + + + + + 94 4.4 BACK TITRATION CURVES For every test carried out using the standard Sobek procedure and the Sobek procedure at under- and over-estimated fizz ratings, the amount of base titrated to obtain pH values at increments from the starting pH up to the end point pH of 7.0 was recorded and back titration curve is plotted. The back titration curves for some samples are provided in Appendix III. Figure 4-18 is an example of back titration curves. In the figure, the X-axes are plotted in milli-equivalents of H 2 S0 4 per gram of sample, converted from the amounts of base added. To illustrate the potential usefulness of considering back titration curves, Figure 4-18 is discussed as follows. This figure is the titration curve for moderate-fizz sample 201-WR, which was tested with acid additions corresponding to slight, moderate and strong fizz ratings. The difference in the shape of the curves, particularly the presence and size of an inflection in the curve between the pH 4 to 5, is evident with a change in the fizz category. This can be seen in the curve which has a significant inflexion point at pH 4-5 when the acid added increase from slight to moderate. The corresponding NP values increased from 36 to 78 (kg CaC03/t). The aluminum concentration of the leachate (Table 4-13) increased correspondingly from 14.2 mg/L to 50.0mg/L. As evident from the data in Table 4-13, other cations exhibit similar increases. 95 As discussed in Chapter 2, there are various minerals which can neutralize ARD. Different minerals weather at different rates depending on pH and other conditions. Sverdrup (1990) and Kwong (1993) have presented as a series of differential weathering of minerals in Table 2-1. Since a less or greater quantity of the minerals in a sample will be dissolved under the digestion conditions of the NP procedure depending on the amount of acid added, the constituent elements in those minerals will be in solution in less or greater amounts during the digestion. If base is added, these metal ions will precipitate within a characteristic pH range for the individual ions present. As precipitation occurs, the solution is temporarily buffered within the specific pH range. For the back titration in the Sobek procedure, for which the specified end-point is pH 7, aluminum is the principal element which will precipitate in the pH range 4 to 5. The amount of aluminum dissolved, and therefore the degree of aluminum silicate mineral dissolution, will be reflected by the shape of the back-titration curve in this pH range. For sample 201-WR, at the moderate fizz, the presence of aluminum in the leachate is clearly indicated, whereas at the lower fizz category, only a slight inflection can be noted. A higher amount of aluminum, calcium, magnesium, sodium, potassium and iron leached under strong-fizz conditions is also indicated. Comparison of the NP data for this sample obtained by the different methods, including the Sobek tests at difference fizz ratings, shows that the NP obtained at the lowest fizz category (slight) is in close agreement with the values obtained using the Modified and Carbonate NP methods (Table 4-1 and Table 4-3). NP values obtained at the two higher fizz categories are significantly greater. 96 The difference in the back titration curves shown for sample 201-WR can also be seen for a large number of the titration curves for the other samples (Appendix III). Inspection of a back titration curve for many samples can indicate, therefore, if the NP value might be overestimated for a specific test procedure. In this study, full back titration curves were constructed for 107 samples tested with different acid conditions. Of these, overestimation of NP relative to the other test methods could be predicted from the shape of the back titration curve for a high percentage of the samples when tested under the standard fizz ratings. Samples for which back titration curves failed to indicated overestimation of NP were mainly low NP samples by any method. Therefore, back titration curves cannot be used by themselves to provide certainty of the overestimation of NP in all cases. However, this study has shown a high success rate in indicating overestimation. Combination of this technique with knowledge of sample mineralogy can be useful as a supplemental predictive tool for a specific application. Sample 201-WR 201-WR 201-WR Fizz Slight Moderate Strong Weight (g) 2 2 2 HCI (vol) 40 40 80 HCI (N) 0 1 05 05 NaOH (N) 0 1 05 0.5 PH NaOH ml mg equiv acid per g kg CaC03 per tonne PH NaOH ml mg equiv acid per g kg CaC03 per tonne PH NaOH ml mg equiv acid per g kg CaC03 per tonne 1.40 0.00 0.96 0.00 10.000 500.0 0.46 0.00 20.000 1000.0 2.0 0.00 2.0 21.93 4.518 225 9 2.0 49 42 7.645 382.3 2.5 0 00 2.000 100.0 2.5 24.95 3.763 188.1 2.5 63.10 4225 211.3 3.0 10.22 1.489 74.5 3 0 25.97 3.508 175.4 3.0 64 38 3 905 195.3 3.5 13.14 1.343 67.2 3.5 26.48 3.380 169.0 3 5 64 98 3.755 187.8 4.0 14.10 1.295 64 8 40 26.87 3283 164.1 4 0 65.83 3543 177.1 4.5 15.57 1.222 61.1 4.5 28.71 2823 141.1 4.5 67.58 3.105 155.3 5.0 19.87 1.007 503 5.0 31.47 2.133 106.6 5.0 70.67 2.333 116.6 6.0 22.10 0.895 448 6.0 32 33 1.918 95 9 6.0 71.76 2.060 103.0 7.0 25.82 0.709 35.5 7.0 33.75 1.563 78 1 7.0 72.54 1.865 93.2 7 00 7 00 1 00 2.000 3.000 mg acid / g 5 000 0 000 1.000 2.000 3.000 mg acid / g 4000 5 000 2.000 3.000 mg acid / g Figure. 4-18 Back Titration Curve for 201-WR (standard fizz: Moderate, C02 NP=20, Modified NP=27) 98 4.5 MINERALOGICAL ANALYSIS BYXRD The results of NP determination presented in the preceding sections have indicated that differences in NP values for the same sample can be attributed to varying degrees of dissolution of the constituent minerals under the different test conditions. Interpretation of static test results, particularly of NP, would be greatly facilitated, therefore, by knowledge of mineralogical composition. In other studies, for example, Lapakko 1994, detailed mineralogical data have enabled researchers to enhance their interpretative ability. In this study, mineralogical analyses of 29 samples by X-ray powder diffraction was conducted. Samples were selected to represent all the mines. Minerals identified in the analyses are indicated in Table 4-15 (a and b). It should be noted that a typical XRD detection limit on a component mineral is around 5% by weight. If the mineral is calcite, for example, 5% is equivalent to a NP value of 50 kg/t, which is very significant. Many rock components, which can prove to be significant neutralizes, might have lower NP values. Detection of component minerals with concentration less than 5% can be, therefore, critical in the assessment of ARD potential but difficult to achieve by XRD analysis. This problem is compounded by the fact that most samples will contain more than one acid consuming minerals, making mineral detection even more difficult when the total NP value is relatively low. 99 The results of the XRD analyses shown in Table 4-15 (a and b) do not provide any definitive assistance in the interpretation of specific NP values or in the differences in the NP data between the various methods of determination. As can be noted from Table 4-15 (a and b), 12 samples have a carbonate NP value greater than 30 as determined by inorganic carbon analysis (>3% CaC0 3 equivalent). Out of the 12 samples, the XRD analyses did not detect either calcite or dolomite in 5 samples. Of the 13 samples in which calcite or dolomite were detected, 5 samples had NP values lower than 20 kg/t (<2% CaC0 3 equivalent). Furthermore, none of the analyses suggested the presence of the more reactive silicates such as anorthite, olivine, or diopside. Plagioclase was often identified but specific minerals of the plagioclase series were not distinguished. The end-members albite and anorthite exhibit significantly different reactivity. The additional problem of providing a definitive composition by weight of the minerals using XRD make this technique of limited value for making sharp distinctions in the interpretation of NP data. Microscopic techniques, such as thin section or reflected light, together with visual examination by experienced geologists are probably the great aid to the interpretation of NP data. Given the importance of understanding the mineralogy of a specific orebody, the input of the geologist in the initial sampling program for a waste characterization study and in the interpretation of results is strongly recommended. 100 4.6 THE TEST RESULTS FOR REFERENCE STANDARD NBM-1 In this study, the reference standard NBM-1 was analyzed for NP by the standard Sobek procedure, Sobek with lower and higher acid additions (according to lower and higher fizz ratings), the Modified ABA procedure, three additional Modified procedures using the different pH values at the end of digestion, C0 2 analysis and the Lapakko method. The results of the NP determinations, together with the corresponding calculated Net NP and NP:AP ratio values based on the sulfur assay assigned to the material, are shown in Table 4-16. The following observations can be made: If the Net NP is used as the criteria for classification, This sample will be safe according to the Sobek (high fizz), Sobek Std, Sobek (low fizz), Inter-laboratory Study, Modified (end pH 8.3) and Modified (end pH 2.5) but not safe according to Modified (end pH 3.0), Modified (end pH 6.6) and Lapakko method. If the NP:AP ratio is used as the criterion for classification, This sample will be safe according to the Sobek (high fizz), Sobek Std, Sobek (low fizz), Inter-laboratory Study, will be low acid generating according to Modified (end pH 8.3), Modified (end pH 2.5), 101 Modified (end pH 3.0) and Modified (end pH 6.6), will be possibly acid generating according to Lapakko method. The proceeding results confirm that the NP value of Sample NBM-1 varies widely. If the Net NP and the NP:AP ratio are used as the criteria for classification, this sample could be classified as either "safe" or "unsafe" according to the different test to be carried out. Furthermore, because different jurisdiction has different regulatory guidelines, the sample could be judged either "safe" or "unsafe" at different jurisdictions. Table 4-16. The Results for Sample NBM-1 Test Method NP NetNP NP:AP (kg CaC03)/t (kg CaC03)/t Sobek (high fizz) 95.2 85.9 10.2 Sobek (standard fizz) 61.1 51.8 6.6 Sobek (low fizz) 41.1 32.1 4.5 Modified (standard end pH) 34.7 25.4 3.7 C 0 2 analysis 33.9 24.6 3.6 Modified (end pH 2.5) 30.2 20.9 3.2 Modified (end pH 3.0) 27.1 17.8 2.9 Modified (end pH 6.6) 24.0 14.7 2.6 Lapakko 15.8 6.5 1.7 Two important conclusions can be drawn from these results: 102 1. For sample NBM-1 itself, the NP values obtained largely depend on the test conditions. Different labs and NP procedures can get different NP values, so, the use of a "certified" NP value for this material can not be claimed. 2. As a reference material, this sample could be useful if the NP value is determined using the same procedure being used to test a group of samples of unknown NP. Since the NP value of the material has been shown in this study to range from 16 to 95 kg/t, the value obtained by using a specific procedure will provide an indication of the possible over- or under-estimation of NP values obtained for the sample group. 103 5 . 0 C O N C L U S I O N S A N D R E C O M M E N D A T I O N S This study has been conducted 111 mining waste and 8 reference standard materials to evaluate various ABA methods for determining neutralization potential in acid rock drainage prediction. For all 119 samples, the following experiments and tests have been conducted: Comparison of the neutralization potentials obtained by the Sobek acid base accounting method and the Modified acid base accounting method, as well as by inorganic carbon (Carbonate NP) analysis. • Comparison of the neutralization potentials obtained in the Sobek procedure using different fizz ratings to determine the effect of acid addition on NP value during the digestion stage. Back titration curves have been plotted based on the data obtained during the titration stage in Sobek procedure at standard, underestimated and overestimated fizz ratings to determine if the shape of the curves can provide an indication of the extent of silicate mineral dissolution during digestion. In addition, the following experiments and tests were conducted using selected samples: Comparison of neutralization potentials obtained by the Lapakko method with the values obtained by the Sobek NP, Modified NP and Carbonate NP. 104 • Mineralogical analyses to determine mineralogical content of samples and the relationship between mineralogical content and the neutralization potential of a sample. The NP values obtained using the Sobek procedure were compared with the NP values determined by the Modified procedure and C0 2 analysis. It was observed that the Sobek method tends to overestimate of the NP value of a sample. C0 2 analysis gives an measurement of the carbonate content of a sample and, therefore, gives a NP value based on the carbonate content in the sample. In the modified method, the NP contribution from silicate minerals is not amplified to the same extent as in the Sobek method. Since in the modified method, sample digestion is carried out at room temperatures and the digestion end pH is controlled within a pre-set narrow range in order to standardize the quantity of acid dosage. The NP values obtained from the modified and from the C 0 2 method correlated well. But for almost all the samples tested (except 2 very low NP samples), NP values obtained by the modified and C0 2 procedures were lower than the NP value by the Sobek method by up to 100%. The higher NP values obtained from the Sobek method can be attributed to the fact that under the higher acidity and boiling conditions in the Sobek test, many minerals classified as intermediate or slow weathering (mainly silicates ) in the environment are likely to contribute to the NP value. Under normal conditions found in waste rock and tailings, such minerals are unlikely to contribute significantly to acid neutralization. 105 According to Lapakko method, samples are titrated with sulfuric acid down to pH 6.0. It was found that the method gives much lower NP values than the standard Sobek method. It provides a better estimation of NP contributed by calcium carbonate and magnesium carbonate in a sample. However, the test is very time consuming and is not suitable for routine assessment of large numbers of samples. So in practice its employment is limited. In the Sobek method, it was also found that, for a sample, the NP value is strongly dependent on the amount of acid added corresponding to the different fizz ratings. If the fizz rating is higher, NP values would be higher accordingly. So, it is recommended that in using the Sobek test, full attention should be paid when carrying out the fizz test. Otherwise, the test results and the results interpretation be much different. Another problem is that fizz test is very subjective. So, in assessing and interpreting the NP results, it is recommended that the test conditions, the fizz rating and the digestion end pH should also be included as part of NP determination results. The practice of eliminating the fizz test and adding only the maximum acid quantity specified by the Sobek procedure should be avoided. The disparity in NP values due to different methods used and to different fizz ratings assigned becomes extremely important when these data are used by regulatory authorities to classify waste materials as either "safe" or "unsafe" for uncontrolled disposal. The criteria used are based on the Net NP value and/or the NP:AP ratio. The NP:AP ratio has 106 become more extensively used recently. The data obtained in this study indicate that a large number of samples can be either classified according to the Net NP and NP:AP ratio as "safe" when using standard Sobek NP or "unsafe" when a different method is used to determine NP. Thus, the use of an overestimated NP value in calculating the Net NP and NP:AP ratio could potentially endanger the environment since waste materials classified as "safe" and disposed improperly could result in ARD generation. On the other hand, the use of an underestimated NP value may result in the unnecessary use of an expensive disposal method placing a high financial burden on the mining company. Back titration curves were plotted in the Sobek tests at standard, underestimated and overestimated fizz ratings all showed that the curve shape can provide an indication of the minerals contributing to the NP value. It was observed in many Sobek tests that the buffering capacities of the solutions reached maximum in the pH range 4 to 5. This may attributed to the precipitation of aluminum dissolved from silicate minerals during the digestion stage. The silicate dissolution became more pronounced when higher fizz rating was assigned and greater acid dosage was applied. Therefore, the plotting of back titration curves can provide qualitative assessment of sample mineralogy contributing to NP. It is recommended that the back titration curve should be attached to the Sobek ABA test results if it is possible to get a better result interpretation. The mineralogical analysis potentially provides a insight look of mineralogical composition of a sample. Theoretically, it is a very useful supplemental test for the 107 understanding and interpretation of static test results. In practice, however, the 29 mineralogical analyses performed in this study largely failed to distinguish the neutralizing minerals, particularly when NP value were moderate to low. For the reference sample NBM-1, the NP values ranged from 15.8 (Lapakko method) to 95.2 (Sobek method with a higher fizz rating). Corresponding Net NP values ranged from 6.5 to 85.9. NP:AP ratio values ranged from 1.7 to 10.2. This has shown that this sample is very useful to be used as a reference sample but a "certified" NP value. These results show once more the concern for potentially serious misclassification of samples in acid base accounting test and the need to conduct the tests in a more systematic manner. It should be noted that determination of NP by even the most ideal static method does not address the important issue of the rate and extent to which a sample will provide neutralization under environmental conditions. Further testing of samples is usually recommended using kinetic test procedures to determine the rate and extent of sulfide mineral oxidation, the rate and extent of the depletion of neutralization potential and the resulting water quality over a range of test conditions. If the rate at which acidity is generated exceeds the rate at which it can be neutralized, ARD conditions can arise even though neutralization minerals are still present in theoretical excess. To get a confident and accurate predictive result, a tool-box approach, a combination of the detailed mineralogical characterization, comparisons with other sites, drainage monitoring, static 108 laboratory tests, kinetic laboratory tests, on-site field trials and other analyses should be carried out. This study has not addressed the other critical aspect of static testing for acid drainage prediction, the determination of the acid potential, AP. Although this is not considered to be as complicated an issue as the neutralization potential, current test methods for AP, the assumptions made in the tests, and the way in which data are interpreted, are subject to similar issues that have been highlighted in this study of NP determination. 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A., 1990, Oxide Zone Geochemistry, Ellis Horwood, Chichester, 286 p. 115 APPENDIX I THE STANDARD ACID BASE ACCOUNTING PROCEDURE OF SOBEK E T A L (1978) The Standard Acid Base Accounting Procedure of Sobek et al (1978) is as follows: 1. Submit a sample of the test material for total sulphur analysis. 2. Use certified 0.1 N hydrochloric acid to standardize the 0.1 N and 0.5 Sodium hydroxide solutions, and then use the sodium hydroxide solutions to standardize the 0.1 N and 0.5 N hydrochloric acid solutions. 3. Place approximately 0.5 g of sample (minus 60 mesh) on a piece of aluminum foil or in a small shallow dish. Add one or two drops of 25 percent HCI to the sample. The presence of carbonate will be indicated by a bubbling or an audible "fizz". Rate the "fizz" as indicated in Table 2-1. 4. Weigh 2.00 g of the sample (minus 60 mesh) into a 250 ml Erlenmeyer flask and add the volume and normality of HCI as indicated by the "fizz" rating in Table 2-2. 5. Heat the pulp nearly to boiling, swirling the flask frequently until reaction is complete, indicated when no further gas evolution is visible and particles settle evenly over the bottom of the flask. 116 6. Add distilled water to make a total volume of 125 ml and boil contents of flask for 1 minute. Cool to slightly above room temperature. Cover tightly and cool to room temperature. 7. Titrate the contents of the flask using 0.1 N or 0.5 N NaOH (corresponding to the normality of HC1 used in step 4) to pH 7.0. Titrate with NaOH until a constant reading of 7.0 remains for at least 30 seconds. Table 2-2. Volume and Normality of HC1 for Use in the Sobek NP Determinations Based on the Fizz Rating (2g sample) Fizz Rating Acid Normality Acid Volume (ml) None 0.1 20 Slight 0.1 40 Moderate 0.5 40 Strong 0.5 80 117 APPENDIX II THE MODIFIED ACID BASE ACCOUNTING PROCEDURE OF LAWRENCE AND WANG (1997) The modified ABA procedure used for this investigation was as follows: 1. Carry out a fizz test an determine the fizz rating of the sample according to the Sobek method. 2. Weigh out 2.00 g of the sample into a 250 ml Erlenmeyer flask and add approximately 90 ml of distilled water. Add a volume of standardized 1.0 N hydrochloric acid according to the fizz rating (see Table 2-3). 3. Place flask on a shaking apparatus maintained at 25-35° C for 2 hours. 4. Check the pH and add further acid if pH value is above 2.5 to bring it to the <2.5 range. If the pH is below 2.0, it is okay. 5. Place the flask on the shaker for an additional 20 hours. 6. Check the pH and add further acid if pH value is above 2.5 to bring it to the <2.5 range. If the pH is below 2.0, discard the contents and repeat the test using a lower volume of acid. 7. Place the flask on the shaker for an additional 2 hours. 8. At the end of the shaking period, make up volume to approximately 125 ml with distilled water and record the final pH. 9. Titrate the pulp using 0.5N or IN NaOH and record the volume added to an end point of pH 8.3. 118 10. Calculate the quantity of acid consumed and the NP of the sample: NP = (Acid normality * volume) - (base normality * volume) * 50 / (weight of sample) Table 2-3 Volume and Normality of HC1 for Use in Modified NP Determinations Based on the Fizz Rating (2g sample) Fizz Rating Acid Normality Acid Volume (ml) at time = 0 h at time = 2 h None 1.0 1.0 1.0 Slight 1.0 2.0 1.0 Moderate 1.0 2.0 2.0 Strong 1.0 3.0 2.0 APPENDIX III BACKTITRATION CURVES Sample: 1001-T Fizz category used in test moderate Mass (g) 2.00 HCI (vol) 40.0 HCI (N) 0.50 NaOH (N) 0.50 Acid NaOH Equivalent PH (ml) (mg eq/q) 1.0 0.00 10.000 2.0 26.29 3.428 2.5 27.76 3.060 3.0 28.42 2.895 3.5 28.86 2.785 4.0 29.67 2.583 4.5 31.57 2.108 5.0 32.02 1.995 6.0 32.99 1.753 7.0 34.51 1.373 Fizz Rating: strong Method: Sobek (alternate fizz rating) Measured NP: 69 kg CaC03/t Sample: 1001-T 2.000 3.000 Add equivalent (mg sq/g) Fizz category used in test strong Mass (g) 2.00 HCI (vol) 80.0 HCI (N) 0.50 NaOH (N) 0.50 Acid NaOH Equivalent PH (ml) (mg eq/g) 0.7 0.00 20.000 2.0 58.40 5.400 2.5 59.64 5.090 3.0 60.17 4.958 3.5 60.67 4.833 4.0 62.32 4.420 4.5 64.38 3.905 5.0 64.62 3.795 6.0 65.75 3.563 7.0 67.38 3.155 Fizz Rating: strong Method: Sobek (alternate fizz rating) Measured NP: 158 kg CaC03/t Sample: 1001-T I i \ I llllttll Ijllf jljllf IHSII Ijllf jljllf 4.000 5.000 6.000 Acid equivalent (mg eq/g) Fizz category used in test strong Mass (g) 2.00 HCI (vol) 80.0 HCI (N) 0.50 NaOH (N) 0.50 Acid NaOH Equivalent PH (ml) (mq eq/g) 0.7 0.00 20.000 2.0 58.40 5.400 2.5 59.64 5.090 3.0 60.17 4.958 3.5 60.67 4.833 4.0 62.32 4.420 4.5 64.38 3.905 5.0 64.82 3.795 6.0 65.75 3.563 7.0 67.38 3.155 Fizz Rating: strong Method: Sobek (alternate fizz rating) Measured NP: 158 kg CaC03/t .000 5.000 6.000 Add equivalent (mg eq/g) Sample: 1002 WR Fizz category used in test slight Mass (g) 2.00 HCI (vol) 40.0 HCI (N) 0.10 NaOH (N) 0.10 Acid NaOH Equivalent PH (ml) (mq eq/q) 1.4 0.00 2.000 2.0 18.99 1.051 2.5 22.86 0.857 3.0 24.45 0.778 3.5 25.26 0.737 4.0 25.96 0.702 4.5 27.05 0.648 5.0 27.66 0.617 6.0 28.27 0.587 7.0 29.07 0.547 Sample: 1003 WR Fizz category used in test none Mass (g) 2.00 HCI (vol) 20.0 HCI (N) 0.10 NaOH (N) 0.10 Acid NaOH Equivalent PH (ml) (mg eq/q) 1.000 2.0 0.00 1.000 2.5 3.22 0.839 3.0 4.27 0.787 3.5 5.08 0.746 4.0 6.76 0.662 4.5 7.99 0.601 5.0 8.89 0.556 6.0 10.50 0.475 7.0 12.02 0.399 Fizz Rating: moderate Method: Sobek (alternate fizz rating) Measured NP: 27.3 kg CaC03/t Sample: 1002 WR .000 1.500 2.000 Acid equivalent (mg eq/g) Fizz Rating: slight Method: Sobek (alternate fizz rating) Measured NP: 20 kg CaC03/t 5 1.000 2.000 3.000 Add equivalent (mg eq/g) Fizz category used in test moderate Mass (g) 2.00 HCI (vol) 40.0 HCI (N) 0.50 NaOH (N) 0,50 Acid NaOH Equivalent PH (ml) (mg eq/q) 0.8 0.00 10.000 2.0 32.21 1.948 2.5 33.52 1.620 3.0 34.82 1.295 3.5 35.34 1.165 4.0 35.70 1.075 4.5 36.23 0.943 5.0 36.51 0.873 6.0 36.74 0.815 7.0 37.06 0.735 Sample: 1003 WR Fizz category used in test slight Mass (g) 2.00 HCI (vol) 40.0 HCI (N) 0.10 NaOH (N) 0.10 Acid NaOH Equivalent PH (ml) (mg eq/g) 1.6 0.00 2.000 2.0 10.09 1.496 2.5 13.87 1.307 3.0 15.52 1.224 3.5 16.68 1.166 4.0 19.79 1.011 4.5 22.08 0.896 5.0 23.36 0.832 6.0 26.19 0.691 7.0 27.85 0.608 Fizz Rating: moderate Method: Sobek (alternate fizz rating) Measured NP: 37 kg CaC03/t Sample: 1002 WR \ 1,000 but. _.uul 2.500 Add equivalent (mg eq/g) Fizz Rating: slight Method: Sobek (alternate fizz rating) Measured NP: 30 kg CaC03/t 000 2.000 3.000 Add equivalent (mg eq/g) Fizz category used in test strong Mass (g) 2.00 HCI (vol) 80.0 HCI (N) 0.50 NaOH (N) 0.50 Acid NaOH Equivalent PH (ml) (mq eq/g) 0.6 0.00 20.000 2.0 68.70 2.825 2.5 70.30 2.425 3.0 72.22 1.945 3.5 72.83 1.793 4.0 73.24 1.690 4.5 73.93 1.518 5.0 74.20 1.450 6.0 74.41 1.398 7.0 74.80 > 1.300 Sample: 1003 WR Fizz category used in test moderate Mass (g) 2.00 HCI (vol) 40.0 HCI (N) 0.50 NaOH (N) 0.48 Acid NaOH Equivalent PH (ml) (mq eq/q) 1.4 0.00 10.000 2.0 23.28 4.413 2.5 24.87 4.031 3.0 25.76 3.818 3.5 26.56 3.626 4.0 27.67 3.359 4.5 31.30 2.488 5.0 32.59 2.178 6.0 34.00 1.840 7.0 35.01 1.598 Fizz Rating: moderate Method: Sobek (alternate fizz rating) Measured NP: 65 kg CaC03/t 1.500 2.000 2.500 Add equivalent (mg eq/g) Fizz Rating: slight Method: Sobek (alternate fizz rating) Measured NP: 80 kg CaC03/t 2.000 3.000 4.000 Add equivalent (mg eq/g) ACID BASE ACCOUNTING TEST RESULTS / TITR_TEM.XLS 07/02/98 Sample: 1101 WR Fizz category used in test slight Mass (g) 2.00 HCI (vol) 40.0 HCI (N) 0.10 NaOH (N) 0.10 Acid NaOH Equivalent PH (ml) (mq eq/q) 1.6 0.00 2.000 2.0 13.13 1.344 2.5 17.56 1.122 3.0 19.18 1.041 3.5 19.84 1.008 4.0 20.33 0.984 4.5 20. S3 0.959 5.0 21.18 0.941 6.0 22.32 0.884 7.0 23.93 0.804 Fizz Rating: moderate Method: Sobek (alternate fizz rating) Measured NP: 40 kg CaC03/t Sample: 1101 WR Acid equivalent (mg eq/g) Fizz category used in test moderate Mass (g) 2.00 HCI (vol) 40.0 HCI(N) 0.50 NaOH (N) 0.48 Acid NaOH Equivalent PH (ml) (mq eq/q) 0.9 0.00 10.000 2.0 33.70 1.912 2.5 34.70 1.672 3.0 35.00 1.600 3.5 35.12 1.571 4.0 35.20 1.552 4.5 35.58 1.461 5.0 35.66 1.442 6.0 35.88 1.389 7.0 36.08 1.341 Fizz Rating: moderate Method: Sobek (alternate fizz rating) Measured NP: 67 kg CaC03/t Sample: 1101 WR Acid equivalent (mg eq/g) Fizz catego y used in test strong Mass (g) 2.00 HCI (vol) 80.0 HCI (N) 0.50 NaOH (N) 0.48 Acid NaOH Equivalent PH (ml) (mq eq/q) 0.6 0.00 20.000 2.0 71.28 2.893 2.5 72.25 2.660 3.0 72.75 2.540 3.5 72.86 2.514 4.0 73.16 2.442 4.5 73.56 2.346 5.0 73.58 2.341 6.0 73.92 2.259 7.0 74.14 2.206 Fizz Rating: Method: moderate Sobek (alternate fizz rating) Measured NP: 110 kg CaC03/t V-< I. - I ) 2.400 2.600 2.800 3.000 Add equivalent (mg eq/g) Sample: 1102 WR Fizz category used in test slight Mass (g) 2.00 HCI (vol) 40.0 HCI (N) 0.10 NaOH (N) 0.10 Acid NaOH Equivalent PH (ml) (mq eq/g) 2.000 2.2 0.00 2.000 2.5 4.00 1.800 3.0 4.50 1.775 3.5 4.75 1.763 4,0 5.04 1.748 4.5 5.46 1.727 5.0 5.68 1.716 6.0 7.73 1.614 7.0 8.69 1.566 Fizz Rating: moderate Method: Sobek (alternate fizz rating) Measured NP: 78 kg CaC03/t Sample: 1102 WR \ 1.500 2.000 Acid equivalent (mg eq/g) Fizz category used in test moderate Mass (g) 2.00 HCI (vol) 40.0 HCi (N) 0.50 NaOH (N) 0.48 Acid NaOH Equivalent PH (ml) (mq eq/q) 1.3 0.00 10.000 2.0 32.00 2.320 2.5 32.66 2.162 3.0 33.05 2.068 3.5 33.28 2.013 4.0 33.55 1.948 4.5 33.82 1.863 5.0 34.13 1.809 6.0 34.62 1.691 7.0 34.90 1.624 Fizz Rating: moderate Method: Sobek (alternate fizz rating) Measured NP: 81 kg CaC03/t Sample: 1102 WR 1.500 2.000 Add equivalent (mg eq/g) Fizz category used in test strong Mass (g) 2.00 HCI (vol) 80.0 HCI (N) 0.50 NaOH (N) 0.48 Acid NaOH Equivalent PH (ml) (mq eq/q) 1.0 0.00 20.000 2.0 70.43 3.097 2.5 71.36 2.874 3.0 71.96 2.730 3.5 72.21 2.670 4.0 72.67 2.559 4.5 72.97 2.487 5.0 73.27 2.415 6.0 73.81 2.286 7.0 74.13 2.209 Fizz Rating: Method: moderate Sobek (alternate fizz rating) Measured NP: 110 kg CaC03/t 2.500 3.000 Add equivalent (mg eq/g) Sample: 1103 WR Fizz category used in test slight Mass (g) 2.00 HCI (vol) 40.0 HCI (N) 0.10 NaOH (N) 0.10 Acid NaOH Equivalent PH (ml) (mq eq/q) 2.000 2.000 2.000 2.000 2.000 2.000 4.3 0.00 2.000 5.0 0.B5 1.958 6.0 3.79 1.811 7.0 4.07 1.797 Fizz Rating: strong Method: Sobek (alternate fizz rating) Measured NP: 90 kg CaC03/t Sample: 1103 WR 500 2.000 2.500 Add equivalent (mg eq/g) Fizz category used in test moderate Mass (g) 2.00 HCI (vol) 40.0 HCI (N) 0.50 NaOH (N) 0.48 Acid NaOH Equivalent PH (ml) (mq eq/q) 1.4 0.00 10.000 2.0 29.30 2.968 2.5 29.84 2.838 3.0 30.25 2.740 3.5 30.55 2.668 4.0 31.06 2.546 4.5 31.51 2.438 5.0 31.92 2.339 6.0 33.55 1.948 7.0 33.89 1.866 Fizz Rating: strong Method: Sobek (alternate fizz rating) Measured NP: 93 kg CaC03/t Sample: 1103 WR 2.000 2.500 3.000 Add equivalent (mg eq/g) Fez category used in test strong Mass (g) 2.00 HCI (vol) 80.0 HCI (N) 0.50 NaOH(N) 0.48 Acid NaOH Equivalent pH (ml) (mq eq/q) 1.1 0.00 20.000 2.0 67.98 3.685 2.S 69.21 3.390 3.0 69.80 3.248 3.5 70.38 3.109 4.0 70.66 3.042 4.5 71.24 2.902 5.0 71.46 2.850 6.0 72.66 2.562 7.0 73.16 2.442 Fizz Rating: strong Method: Sobek (alternate fizz rating) Measured NP: 122 kg CaC03/t 2.500 3.000 3.500 Add equivalent (mg eq/g) ACID BASE ACCOUNTING TEST RESULTS / TITR_2.XLS 07/02/98 Sample: 1203 T Fizz category used in test Slight Mass (g) 2.00 HCI (vol) 40.0 HCI (N) 0.10 NaOH (N) 0.10 Acid NaOH Equivalent pH (ml) (mg eq/g) 2.000 2.000 2.000 2.000 2.000 2.000 2.000 5.0 0.00 2.000 6.0 0.71 1.965 7.0 1.89 1.906 Fizz Rating: strong Method: Sobek (alternate fizz rating) Measured NP: 95 kg CaC03/t Sample: 1203 T JUL 3.000 4.000 Acid equivalent (mg eq/g) Fizz category used in test Moderate Mass (g) 2.00 HCI (vol) 40.0 HCI (N) 0.50 NaOH (N) 0.55 Acid NaOH Equivalent PH (ml) (mq eq/q) 0.9 0.00 10.000 2.0 13.31 6.373 2.5 13.94 6.201 3.0 14.34 6.092 3.5 14.91 5.937 4.0 17.95 5.109 4.5 19.90 4.577 5.0 20.16 4.506 6.0 21.56 4.125 7.0 24.36 3.362 Fizz Rating: strong Method: Sobek (alternate fizz rating) Measured NP: 168 kg CaC03/t Sample: 1203 T 4.000 5.000 6.000 Acid equivalent (mg eq/g) Fizz category used in test Strong Mass (g) 2.00 HCI (vol) 80.0 HCI (N) 0.50 NaOH (N) 0.55 Acid NaOH Equivalent PH (ml) (mq eq/g) 0.5 0.00 20.000 2.0 50.45 6.252 2.5 51.65 5.925 3.0 52.14 5.792 3.5 52.87 5.593 4.0 56.69 4.552 4.5 58.15 4.154 5.0 58.57 4.040 6.0 59.25 3.854 7.0 59.83 3.696 Fizz Rating: strong Method: Sobek (alternate fizz rating) Measured NP: 185 kg CaC03/t 4.000 5.000 6.000 Acid equivalent (mg eq/g) Sample: 1204 WR Fizz category used in test Slight Mass (g) 2.00 HCI (vol) 40.0 HCI (N) 0.10 NaOH (N) 0.10 Acid NaOH Equivalent PH (ml) (mq eq/q) 2.000 2.000 2.000 2.000 2.000 2.000 4.9 0.00 2.000 5.0 0.12 1.994 6.0 1.03 1.949 7.0 1.16 1.942 Fizz Rating: strong Method: Sobek (alternate fizz rating) Measured NP: 97 kg CaC03/t Sample: 1204 WR .... j •{• I iHH|AlplllBIB¥ 2.000 3.000 Add equivalent (mg eq/g) Fizz category used in test Moderate Mass (g) 2.00 HCI (vol) 40.0 HCI (N) 0.50 NaOH (N) 0.55 Acid NaOH Equivalent PH (ml) (mq eq/q) 0.9 0.00 10.000 2.0 22.18 3.956 2.5 23.01 3.730 3.0 23.35 3.637 3.5 23.62 3.564 4.0 24.10 3.433 4.5 24.81 3.239 5.0 25.34 3.095 6.0 26.15 2.874 7.0 26.92 2.664 Fizz Rating: strong Method: Sobek (alternate fizz rating) Measured NP: 133 kgCaC03/t Sample: 1204 WR 3.000 4.000 Add equivalent (mg eq/g) Fizz category used in test Strong Mass (g) 2.00 HCI (vol) 80.0 HCI (N) 0.50 NaOH (N) 0.50 Acid NaOH Equivalent PH (ml) (mq eq/q) 0.5 0.00 20.000 2.0 58.74 5.315 2.5 60.06 4.985 3.0 60.61 4.848 3.5 61.21 4.698 4.0 61.60 4.600 4.5 63.03 4.243 5.0 63.34 4.165 6.0 63.99 4.003 7.0 64.67 3.833 Fizz Rating: strong Method: Sobek (alternate fizz rating) Measured NP: 192 kg CaC03/t 4.000 5.000 Add equivalent (mg eq/g) Sample: 1205 WR Fizz category used in test slight Mass (g) 2.00 HCI (vol) 40.0 HCI (N) 0.10 NaOH (N) 0.10 Acid NaOH Equivalent PH (ml) (mq eq/q) 1.8 0.00 2.000 2.0 3.10 1.845 2.5 6.90 1.655 3.0 B.10 1.595 3.5 6.90 1.555 4.0 10.40 1.480 4.5 13.80 1.310 5.0 14.80 1.260 6.0 16.20 1.190 7.0 19.50 1.025 Fizz Rating: moderate Method: Sobek (alternate fizz rating) Measured NP: 51 kg CaC03/t Sample: 1205 WR 2.000 3.000 Add equivalent (mg eq/g) Fizz category used in test Moderate Mass (g) 2.00 HCI (vol) 40.0 HCI (N) 0.50 NaOH (N) 0.55 Acid NaOH Equivalent PH (ml) (mq eq/q) 0.8 0.00 10.000 2.0 26.75 2.711 2.5 27.41 2.531 3.0 27.78 2.430 3.5 28.19 2.318 4.0 29.49 1.964 4.5 31.16 1.509 5.0 31.54 1.405 6.0 32.13 1.245 7.0 32.96 1.018 Fizz Rating: moderate Method: Sobek (alternate fizz rating) Measured NP: 51 kg CaC03/t Sample: 1205 WR 2.000 3.000 Add equivalent (mg eq/g) Fizz category used in test Strong Mass (g) 2.00 HCI (vol) 80.0 HCI (N) 0.50 NaOH (N) 0.55 Acid NaOH Equivalent PH (ml) (mq eq/q) 0.4 0.00 20.000 2.0 59.33 3.833 2.5 60.59 3.489 3.0 61.17 3.331 3.5 61.78 3.165 4.0 63.17 2.786 4.5 64.77 2.350 5.0 65.26 2.217 6.0 65.73 2.089 7.0 67.09 1.716 Fizz Rating: moderate Method: Sobek (alternate fizz rating) Measured NP: 86 kg CaC03/t lllilllllllll yillllltpilll illW;:i!!!H! Iliiiiiii iiiiiBiii 2.000 3 000 Add equivalent (mg eq/g) ACID BASE ACCOUNTING TEST RESULTS / TITR_3.XLS 07/02/98 Sample: 1206 WR Fizz category used in test Slight Mass (g) 2.00 HCI (vol) 40.0 HCI (N) 0.10 NaOH (N) 0.10 Acid NaOH Equivalent PH (ml) (mq eq/q) 1.7 0.00 2.000 2.0 7.00 1.650 2.5 10.16 1.492 3.0 11.20 1.440 3.5 11.90 1.405 4.0 13.00 1.350 4.5 16.00 1.200 5.0 17.00 1.150 6.0 20.10 0.995 7.0 24.10 0.795 Sample: 201 WR Sample: 202 WR Fizz category used in test Slight Mass (g) 2.00 HCI (vol) 40.0 HCI (N) 0.10 NaOH (N) 0.10 Acid NaOH Equivalent PH (ml) (mq eq/g) 2.000 2.000 1.4 0.00 2.000 3.0 10.22 1.489 3.5 13.14 1.343 4.0 14.10 1.295 4.5 15.57 1.222 5.0 19.87 1.007 6.0 22.10 0.895 7.0 25.80 0.710 Fizz Rating: slight Method: Sobek (alternate fizz rating) Measured NP: 40 kg CaC03/t Sample: 1206 WR 0.500 1.000 1.500 Acid equivalent (mg eq/g) Fizz Rating: moderate Method: Sobek (alternate fizz rating) Measured NP: 36 kg CaC03/t 1.000 2.000 Add equivalent (mg eq/g) Fizz category used in test None Mass (g) 2.00 HCI (vol) 20.0 HCI (N) 0.10 NaOH (N) 0.10 Acid NaOH Equivalent PH (ml) (mq eq/g) 1.000 2.1 0.00 1.000 2.5 2.07 0.897 3.0 2.92 0.854 3.5 3.52 0.824 4.0 5.44 0.728 4.5 7.10 0.645 5.0 7.50 0.625 6.0 10.13 0.494 7.0 13.41 0.330 Fizz Rating: slight Method: Sobek (alternate fizz rating) Measured NP: 16 kg CaC03/t 0.000 0.500 1.000 1.500 2.000 2.500 3.000 Add equivalent (mg eq/g) Fizz categor y used in test Moderate Mass (g) 2.00 HCI (vol) 40.0 HCI (N) 0.50 NaOH (N) 0.55 Acid NaOH Equivalent PH (ml) (mg eq/g) 0.8 0.00 10.000 2.0 22.98 3.738 2.5 23.80 3.515 3.0 24.36 3.362 3.5 24.76 3.253 4.0 25.30 3.106 4.5 26.69 2.727 5.0 27.09 2.618 6.0 28.24 2.305 7.0 29.12 2.065 Sample: 201 WR Fizz category used in test Moderate Mass (g) 2.00 HCI (vol) 40.0 HCI (N) 0.50 NaOH (N) 0.50 Acid NaOH Equivalent PH (ml) (mq eq/q) 1.0 0.00 10.000 2.0 21.93 4.518 2.5 24.95 3.763 3.0 25.97 3.508 3.5 26.43 3.380 4.0 26.87 3.283 4.5 28.71 2.823 5.0 31.47 2.133 6.0 32.33 1.918 7.0 33.75 1.563 Sample: 202 WR Fizz category used in test Slight Mass (g) 2.00 HCI (vol) 40.0 HCI (N) 0.10 NaOH (N) 0.10 Acid NaOH Equivalent PH (ml) (mg eq/g) 1.5 0.00 2.000 2.0 12.08 1.396 2.5 14.62 1.259 3.0 16.23 1.189 3.5 17.25 1.138 4.0 20.60 0.970 4.5 24.03 0.799 5.0 24.79 0.761 6.0 26.63 0.659 7.0 30.03 0.499 Fizz Rating: slight Method: Sobek (alternate fizz rating) Measured NP: 103 kg CaC03/t 2.500 3.000 3.500 Add equivalent (mg eq/g) Fizz Rating: moderate Method: Sobek (alternate fizz rating) Measured NP: 78 kg CaC03/t 2.500 3.500 Add equivalent (mg eq/g) Fizz Rating: slight Method: Sobek (alternate fizz rating) Measured NP: 25 kg CaC03/t 0,000 0.500 1.000 1.500 2.000 2.500 3.000 Add equivalent (mg eq/g) Sample: 201 WR Fizz category used in test Strong Mass (g) 2.00 HCI (vol) 80.0 HCI (N) 0.50 NaOH (N) 0.50 Acid NaOH Equivalent PH (ml) (mq eq/q) 0.5 0.00 20.000 2.0 49.42 7.645 2.5 63.10 4.225 3.0 64.38 3.905 3.5 64.98 3.755 4,0 65.83 3.543 4.5 67.58 3.105 5.0 70.67 2.333 6.0 71.76 2.060 7.0 72.54 1.865 Sample: 202 WR Fizz category used in test Moderate Mass (g) 2.00 HCI (vol) 40.0 HCI (N) 0.50 NaOH (N) 0.63 Acid NaOH Equivalent PH (ml) (mg eq/g) 1.0 0.00 10.000 2.0 18.30 4.202 2.5 19.39 3.856 3.0 19.84 3.714 3.5 20.12 3.625 4.0 21.48 3.194 4.5 23.96 2.408 5.0 24.40 2.269 6.0 25.14 2.034 7.0 26.06 1.743 Fizz Rating: moderate Method: Sobek (alternate fizz rating) Measured NP: 93 kg CaC03/t 2.500 3.500 Add equivalent {mg eq/g) Fizz Rating: slight Method: Sobek (alternate fizz rating) Measured NP: 87 kg CaC03/t 1.500 2.000 2.500 3.000 3.500 4.000 4.500 Add equivalent (mg eq/g) ACID BASE ACCOUNTING TEST RESULTS / TITR_4.XLS 07/02/98 Sample: 209 T Fizz category used in test Slight Mass (g) 2.00 HCI (vol) 40.0 HCI (N) 0.10 NaOH (N) 0.10 Acid NaOH Equivalent PH (ml) (mg eq/g) 1.4 0.00 2.000 2.0 9.60 1.520 2.5 11.55 1.423 3.0 12.53 1.374 3.5 13.90 1.305 4.0 19.18 1.041 4.5 21.64 0.918 5.0 22.10 0.695 6.0 23.82 0.B09 7.0 25.49 0.726 Fizz Rating: mode ] Method: Sobek (alternate fizz rating) Measured NP: 36 kg CaC03/t Sample: 209 T 1.000 2.000 Acid equivalent (mg eq/g) Fizz category used in test Moderate Mass (g) 2.00 HCI (vol) 40.0 HCI (N) 0.50 NaOH (N) 0.63 Acid NaOH Equivalent PH (ml) (mg eq/g) 0.9 0.00 10.000 2.0 21.38 3.226 2.5 22.63 2.830 3.0 23.03 2.703 3.5 23.41 2.583 4.0 24.09 2.367 4.5 26.56 1.584 5.0 26.93 1.467 6.0 27.43 1.309 7.0 28.07 1.106 Fizz Rating: moderate Method: Sobek (alternate fizz rating) Measured NP: 55 kg CaC03/t Sample: 209 T 2.000 3.000 Add equivalent (mg eq/g) Fizz category used in test Strong Mass (g) 2.00 HCI (vol) 80.0 HCI (N) 0.50 NaOH (N) 0.61 Acid NaOH Equivalent PH (ml) (mq eq/q) 0.5 0.00 20.000 2.0 52.52 4.086 2.5 53.93 3.659 3.0 54.67 3.435 3.5 55.31 3.241 4.0 56.18 2.977 4.5 59.28 2.341 5.0 5B.75 2.199 6.0 59.27 2.041 7.0 59.69 1.914 Fizz Rating: moderate Method: Sobek (alternate fizz rating) Measured NP: 96 kg CaC03/t I.5O0 3.500 Add equivalent (mg eq/g) Sample: 210 T Fizz category used in test Slight Mass (g) 2.00 HCI (vol) 40.0 HCI (N) 0.10 NaOH (N) 0.10 Acid NaOH Equivalent pH (ml) (mq eq/g) 1.4 0.00 2.000 2.0 7.65 1.618 2.5 9.28 1.536 3.0 10.26 1.487 3.5 11.94 1.403 4.0 17.99 1.101 4.5 20.66 0.967 5.0 21.07 0.947 6.0 24.28 0.786 7.0 26.27 0.667 Fizz Rating: moderate Method: Sobek (alternate fizz rating) Measured NP: 34 kg CaC03/t Sample: 210 T 1.000 2.000 Add equivalent (mg eq/g) Fizz category used in test Moderate Mass (g) 2.00 HCI (vol) 40.0 HCI (N) 0.50 NaOH (N) 0.50 Acid NaOH Equivalent PH (mi) (mq eq/q) 0.9 0.00 10.000 2.0 21.44 4.640 2.5 22.33 4.418 3.0 22.73 4.318 3.5 23.16 4.210 4.0 24.36 3.910 4.5 27.60 3.100 5.0 28.18 2.955 6.0 29.77 2.558 7.0 30.73 2.316 Fizz Rating: moderate Method: Sobek (alternate fizz rating) Measured NP: 116 kg CaC03/t „JUL 4.000 Add equivalent (mg eq/g) Sample: 211 T Fizz category used in test Slight Mass (g) 2.00 HCI (vol) 40.0 HCI (N) 0.10 NaOH (N) 0.10 Acid NaOH Equivalent PH (ml) (mq eq/q) 1.9 0.00 2.000 2.0 0.75 1.963 2.5 3.05 1.848 3.0 4.04 1.798 3.5 4.96 1.752 4.0 10.00 1.500 4.5 13,80 1.310 5.0 14.45 1.278 6.0 17.69 1.116 70 28.66 0.567 Fizz Rating: moderate Method: Sobek (alternate fizz rating) Measured NP: 28 kg CaC03/t Sample: 211 T 2.000 3 OOO Add equivalent (mg eq/g) Fizz category used in test Moderate Mass (g) 2.00 HCI (vol) 40.0 HCI (N) 0.50 NaOH (N) • 0.63 Acid NaOH Equivalent PH (ml) (mg eq/g) 1.0 0.00 10.000 2.0 16.32 4.829 2.5 17.18 4.557 3.0 17.62 4.417 3.5 17.89 4.332 4.0 18.88 4.018 4.5 21.66 3.137 5.0 22.27 2.944 6.0 23.43 2.576 7.0 25.78 1.832 Fizz Rating: moderate Method: Sobek (alternate fizz rating) Measured NP: 92 kg CaC03/t Sample: 211 T 2 500 3.500 Add equivalent (mg eq/g) Fizz category used in test Strong Mass (g) 2.00 HCI (vol) 80.0 HCI (N) 0.50 NaOH (N) 0.61 Acid NaOH Equivalent PH (ml) (mg eq/g) 0.8 0.00 20.000 2.0 50.29 4.762 2.5 51.02 4.541 3.0 51.51 4.392 3.5 52.17 4.192 4.0 54.32 3.541 4.5 56.61 2.847 5.0 57.02 2.723 6.0 57.98 2.432 7.0 59.78 1.887 Fizz Rating: moderate Method: Sobek (alternate fizz rating) Measured NP: 94 kg CaC03/t 2 500 3.500 Add equivalent (mg eq/g) ACID BASE ACCOUNTING TEST RESULTS / TITR_5.XLS 09/02798 125 II I I IP 11 i l J fx f l I / m II fsiiiijjl l9i§SiSS§ n nnmm I i ! al f f si 2 S 3 S 3 S 5 S S S jg 1 ss 1 .s ! n 0.00 13.46 14.45 14.83 15.12 15.84 18.30 18.85 20.04 22.17 Fizz category Mass (g) HCI (vol) HCI (N) NaOH (N) s s fl i f i i S S 3 S 5 S II l is nnmrn Fizz category used in test Mass (g) HCI (vol) HCI (N) NaOH (N) i t 1133353 Fizz category used in test Mass (g) HCI (vol) HCI (N) NaOH (N) 5 S S ? " s s s i1 1 " | S 5 S S 5 S S If I s | 5 ssssssssss f ! i fl i Slight 2.00 40.0 0.10 0.10 • H immm used in test Fez category Mass (g) HCI (vol) HCI(N) i II Iii | / / / i I ii nnmm .e I If fgs 5 S S S S S 3 3 S S S I ! I i i * i i s | S 2 S 8 3 S 3 S I • ! . 1 I ! ! i § I pins}]! 1SBBS1SS§5 5 " S S S S S 3 8SS I IS 11 i l I • 1 £ is i l l '!! mmim used in test Fizz category Mass (g) HCI (vol) HCI(N) i . 5 S S S S 3 S S S Sample: 307 WR Fizz category used in test None Mass (g) 2.00 HCI (vol) 20.0 HCI (N) 0.10 NaOH (N) 0.10 Acid NaOH Equivalent PH (ml) (mq eq/q) 1.000 2.4 0 00 1.000 2.5 0 60 0.970 3.0 1.90 0.905 3.5 2.60 0.870 4.0 4.00 0.800 4.5 5.50 0.725 5.0 5.90 0.705 6.0 7.20 0.640 7.0 10.20 0.490 Fizz Rating: slight Method: Sobek (alternate fizz rating) Measured NP: 25 kg CaC03/t Sample: 307 WR 2.000 3.000 4.000 Acid equivalent (mg eq/g) Fizz category used in test Slight Mass (g) 2.00 HCI (vol) 40.0 HCI (N) 0.10 NaOH (N) 0.10 Acid NaOH Equivalent PH (ml) (mg Bq/g) 1.7 0.00 2.000 2.0 5.30 1.735 2.5 8.80 1.560 3.0 10.40 1.480 3.5 11.90 1.405 4.0 16.70 1.165 4.5 20.10 0.995 5.0 20.74 0.963 60 22.20 0.890 7.0 26.20 0.690 Fizz Rating: slight Method: Sobek (alternate fizz rating) Measured NP: 35 kg CaC03/t Sample: 307 WR Fizz Rating: Method: \ I \ v 1 2.000 3.000 A Add equivalent (mg eq/g) Fizz category used in test Moderate Mass (g) 2.00 HCI (vol) 40.0 HCI (N) 0.50 NaOH (N) 0.61 Acid NaOH Equivalent PH (ml) (mq eq/q) 1.0 0.00 10.000 2.0 14.20 5.697 2.5 16.34 5.049 3.0 16.99 4.852 3.5 17.40 4.728 4.0 18.28 4.461 4.5 23.08 3.007 5.0 26.42 1.995 6.0 27.91 1.543 7.0 29.70 1.001 slight Sobek (alternate fizz rating) Measured NP: 50 kg CaC03/t 3 3.000 4.000 5.000 6.000 Add equivalent (mg eq/g) Sample: 308 WR Fizz category used in test Slight Mass (g) 2.00 HCI (vol) 40.0 HCI (N) 0.10 NaOH (N) 0.20 Acid NaOH Equivalent PH (ml) (mq eq/q) 2.000 2 000 2.000 3.3 0.00 2.000 3.5 0.65 1.935 4.0 1.93 1.608 4.5 2.47 1.754 5.0 4.33 1.569 6.0 6.93 1.310 7.0 8.93 1.111 Fizz Rating: strong Method: Sobek (alternate fizz rating) Measured NP: 56 kg CaC03/t Sample: 308 WR 1 \ iBiij jiipjiliii HHIIIM 2.000 3.000 4.000 Add equivalent (mg eq/g) Fizz category used in test Moderate Mass (g) 2.00 HCI (vol) 40.0 HCI (N) 0.50 NaOH (N) 0.63 Acid NaOH Equivalent PH (ml) (mg eq/g) 1.2 0.00 10.000 2.0 16.38 4.810 2.5 17.08 4.588 3.0 17.39 4.490 3.5 17.66 4.404 4.0 18.70 4.075 4.5 21.33 3.242 5.0 21.76 3.105 6.0 22.71 2.604 7.0 26.13 1.721 Fizz Rating: strong Method: Sobek (alternate fizz rating) Measured NP: 86 kg CaC03/t Sample: 308 WR pill •mm iliPHll iiiiiii \ •V. (1111111 2.000 3.000 4.00 Add equivalent (mg eq/g) Fizz category used in test Strong Mass (g) 2.00 HCI (vol) 80.0 HCI (N) 0.50 NaOH (N) 0.61 Acid NaOH Equivalent PH (ml) (mq eq/q) 1.1 0.00 20.000 2.0 46.87 5.798 2.5 48.17 5.404 3.0 48.76 5.226 3.5 49.25 5.077 4.0 50.02 4.844 4.5 53.41 3.817 5.0 54.15 3.593 6.0 56.36 2.923 7.0 58.90 2.153 Fizz Rating: strong Method: Sobek (alternate fizz rating) Measured NP: 108 kg CaC03/t Mi • v • Sill Ijilliil •v. 3.000 4.000 5.000 Acid equivalent (mg eq/g) Sample: 309 WR Fizz category used in test Slight Mass (g) 2.00 HCI (vol) 40.0 HCI (N) 0.10 NaOH (N) 0.10 Acid NaOH Equivalent PH (ml) (mq eq/g) 2.000 2.000 2.000 3.1 0.00 2.000 3.5 0.58 1.971 4.0 0.89 1.956 4.5 1.46 1.927 5.0 1.96 1.902 6.0 4.84 1.758 7.0 6.00 1.700 Fizz Rating: strong Method: Sobek (alternate fizz rating) Measured NP: 85 kg CaC03/t Sample: 309 WR — - 2.000 3.000 4.000 Acid equivalent (mg eq/g) Fizz category used in test Moderate Mass (g) 2.00 HCI (vol) 40.0 HCI(N) 0.50 NaOH (N) 0.55 Acid NaOH Equivalent PH (ml) (mg  Bq/g) 1.1 0 00 10.000 20 17.10 5.340 2.5 17.60 5.204 3.0 18.30 5.013 3.5 18.60 4.932 4.0 19.10 4.795 4.S 19.80 4.605 5.0 20.50 4.414 60 22.50 3.869 7.0 29.60 1.934 Fizz Rating: strong Method: Sobek (alternate fizz rating) Measured NP: 97 kg CaC03/t Sample: 309 WR - —^_ "V. pi Mil Iflilll IflliU 2.500 3.500 4500 Add equivalent (mg eq/g) Fizz category used in test Strong Mass (g) 2.00 HCI (vol) 80.0 HCI (N) 0.50 NaOH (N) 0.55 Acid NaOH Equivalent PH (ml) (mq eq/q) 0.5 0.00 20.000 2.0 53.40 5.449 2.5 55.20 4.958 3.0 55.90 4.767 3.5 56.60 4.577 4.0 57.50 4.331 4.5 60.04 3.639 5.0 60.85 3.418 6.0 62.85 2.873 7.0 65.26 2.217 Fizz Rating: strong Method: Sobek (alternate fizz rating) Measured NP: 111 kg CaC03/t 3.000 4.000 5.000 Add equivalent (mg eq/g) ACID BASE ACCOUNTING TEST RESULTS / TITR_7.XLS 07/02/98 Sample: 407 WR Fizz category used in test Slight Mass (g) 2.00 HCI (vol) 40.0 HCI (N) 0.10 NaOH (N) 0.10 Acid NaOH Equivalent PH (ml) (mq eq/q) 1.8 0.00 2.000 2.0 5.52 1.724 2.5 12.18 1.391 3.0 14.96 1.252 3.5 16.26 1.187 4.0 17.00 1.150 4.5 17.77 1.112 5.0 18.72 1.064 6.0 20.69 0.966 7.0 22.64 0.666 Fizz Rating: moderate Method: Sobek (alternate fizz rating) Measured NP: 43 kg CaC03/t Sample: 407 WR • slIBJI —m .000 1.500 2.D0O Add equivalent (mg eq/g) Fizz category used in test Moderate Mass (g) 2.00 HCI (vol) 40.0 HCI (N) 0.50 NaOH (N) 0.50 Acid NaOH Equivalent PH (ml) (mq eq/q) 0.7 0.00 10.000 2.0 30.34 2.415 2.5 32.03 1.993 3.0 32.77 1.808 3.5 33.34 1.665 4.0 33.41 1.646 4.5 33.69 1.578 5.0 34.05 1.488 6.0 34.54 1.365 7.0 34.63 1.293 Fizz Rating: moderate Method: Sobek (alternate fizz rating) Measured NP: 65 kg CaC03/t Sample: 407 WR 2.000 2.500 Add equivalent (mg eq/g) Fizz category used in test Strong Mass (g) 2.00 HCI (vol) 80.0 HCI (N) 0.50 NaOH (N) 0.50 Acid NaOH Equivalent PH (ml) (mq eq/q) 0.3 0.00 20.000 2.0 66.95 2.763 2.5 70.87 2.283 3.0 71.80 2.050 3.5 72.37 1.908 4.0 72.72 1.820 4.5 72.96 1.760 5.0 73.32 1.670 6.0 73.73 1.568 7.0 74.19 1.453 Fizz Rating: moderate Method: Sobek (alternate fizz rating) Measured NP: 73 kg CaC03/t 1.500 2 000 2.500 Add equivalent (mg eq/g) Sample: 408 WR Fizz category used in test None Mass (g) 2.00 HCI (vol) 20.0 HCI (N) 0.10 NaOH (N) 0.10 Acid NaOH Equivalent PH (ml) (mg eq/g) 1.000 2.1 0.00 1.000 2.5 4.90 0.755 3.0 7.69 0.616 3.5 8.60 0.570 4.0 9.20 0.540 4.5 9 61 0.520 5.0 10.50 0.475 6.0 11.80 0.410 7.0 14.20 0290 Fizz Rating: none Method: Sobek (alternate fizz rating) Measured NP: 15 kg CaC03/t Sample: 408 WR 0.400 0.600 0 BOO Add equivalent (mg eq/g) Fizz category used in test Slight Mass (g) 2.00 HCI (vol) 40.0 HCI (N) 0.10 NaOH (N) 0.10 Acid NaOH Equivalent PH (ml) (mg eq/g) 1.5 0.00 2.000 2.0 17.84 1.108 2.5 24.12 0.794 3.0 27.50 0.625 3.5 28.61 0.570 4.0 29.49 0.526 4.5 30.05 0.498 5.0 30.85 0.458 6.0 32.2B 0.366 7.0 33.84 0.308 Fizz Rating: none Method: Sobek (alternate fizz rating) Measured NP: 15 kg CaC03/t Sample: 408 WR 0.400 0.6O0 0.BOO Add equivalent (mg eq/g) Fizz category used in test Moderate Mass (g) 2.00 HCI (vol) 40.0 HCI (N) 0.50 NaOH (N) 0.61 Acid NaOH Equivalent PH (ml) (mq eq/q) 1.2 0.00 10.000 2.0 28.92 1.237 2.5 29.44 1.080 3.0 29.69 1.004 3.5 29.82 0.965 4.0 30.06 0.892 4.5 30.17 0.856 5.0 30.31 0.816 6.0 30.56 0.740 7.0 31.06 0.589 Fizz Rating: none Method: Sobek (alternate fizz rating) Measured NP: 29 kg CaC03/t liiiii lillii ^itiiiii l 7 W 0.7OO 0.900 1.100 1.300 Add equivalent (mg eq/g) Sample: 501 WR Fizz category used in test None Mass (g) 2.00 HCI (vol) 20.0 HCI (N) 0.10 NaOH (N) 0.10 Acid NaOH Equivalent PH (ml) (mq eq/g) 1.000 2.1 0.00 1.000 2.5 4.64 0.768 3.0 7.41 0.630 3.5 8.61 0.570 4.0 9.25 0.536 4.5 9.96 0.502 5.0 10.86 0.457 6.0 12.44 0.378 7.0 14.12 0.294 Fizz Rating: none Method: Sobek (alternate fizz rating) Measured NP: 15 kg CaC03/t Sample: 501 WR 0.400 0.600 0 800 1.000 Add equivalent (mg eq/g) Fizz category used in test Slight Mass (g) 2.00 HCI (vol) 40.0 HCI (N) 0.10 NaOH (N) 0.10 Acid NaOH Equivalent PH (ml) (mq eq/q) 1.6 0.00 2.000 2.0 13.23 1.339 2.5 20.56 0.972 3.0 23.82 0.809 3.5 25.49 0.726 4.0 26.32 0.684 4.5 26.99 0.651 5.0 27.95 0.603 6.0 30.16 0.492 7.0 32.53 0.374 Fizz Rating: none Method: Sobek (alternate fizz rating) Measured NP: 19 kg CaC03/t Sample: 501 WR Add equivalent (mg eq/g) Fez category used in test Moderate Mass (g) 2.00 HCI (vol) 40.0 HCI (N) 0.50 NaOH (N) 0.61 Acid NaOH Equivalent PH (ml) (mq eq/q) 1.2 0.00 10.000 2.0 26.57 1.949 2.5 27.45 1.683 3.0 27.69 1.610 3.5 26.02 1.510 4.0 28.17 1.464 4.5 2B.33 1.416 5.0 2862 1.328 6.0 29.38 1.098 7.0 29.58 1.037 Fizz Rating: none Method: Sobek (alternate fizz rating) Measured NP: 52 kg CaC03/t lljiiil <1 Add equivalent (mg eq/g) ACID BASE ACCOUNTING TEST RESULTS / TITR_8.XLS 07/02/98 Sample: 502 WR Fizz category used in test None Mass (g) 2.00 HCI (vol) 20.0 HCI (N) 0.10 NaOH (N) 0.10 Acid NaOH Equivalent PH (ml) (mq eq/q) 1.000 2.1 0.00 1.000 2.5 5.54 0.723 3.0 8.48 0.576 3.5 9.69 0.516 4.0 10.90 0.455 4.5 13.32 0.334 5.0 15.11 0.245 6.0 16.63 0.169 7.0 18.28 0.086 Fizz Rating: none Method: Sobek (alternate fizz rating) Measured NP: 4.3 kg CaC03/t Sample: 502 WR 0.500 1.000 1.50 Acid equivalent (mg eq/g) Fizz category used in test Slight Mass (g) 2.00 HCI (vol) 40.0 HCI (N) 0.10 NaOH (N) 0.10 Acid NaOH Equivalent PH (ml) (mq eq/q) 1.7 0.00 2.000 2.0 12.17 1.392 2.5 20.11 0.995 3.0 23.10 0.845 3.5 24.70 0.765 4.0 26.11 0.695 4.5 26.94 0.653 5.0 32.78 0.361 6.0 34.61 0.270 7.0 35.83 0.209 Fizz Rating: none Method: Sobek (alternate fizz rating) Measured NP: 10 kg CaC03/t Sample: 502 WR 0.500 1.000 ISC Add equivalent (mg eq/g) Fizz category used in test Moderate Mass (g) 2.00 HCI (vol) 40.0 HCI (N) 0.50 NaOH (N) 0.61 Acid NaOH Equivalent PH (ml) (mg eq/q) 1.2 0.00 10.000 2.0 23.71 2.816 2.5 24.32 2.631 3.0 24.47 2.586 3.5 24.88 2.461 4.0 26.71 1.907 4.5 27.41 1.695 5.0 27.67 1.616 6.0 28.45 1.380 7.0 28.98 1.219 Fizz Rating: none Method: Sobek (alternate fizz rating) Measured NP: 61 kg CaC03/t 1.500 2.000 2.500 Acid equivalent (mg eq/g) Sample: 503 WR Fizz category used in test None Mass (g) 2.00 HCI (vol) 20.0 HCI (N) 0.10 NaOH (N) 0.10 Acid NaOH Equivalent PH (ml) (mg eq/g) 1.000 2.3 0.00 1.000 2.5 1.74 0.913 3.00 4.86 0.757 3.5 6.11 0.695 4.0 7.24 0.638 4.5 9.79 0.511 5.0 11.17 0.442 6.0 12.55 0.373 7.0 14.72 0.264 Fizz Rating: none Method: Sobek (alternate fizz rating) Measured NP: 13 kg CaC03/t Sample: 503 WR 0.500 1.000 1.500 Acid equivalent {mg eq/g) Fizz category used in test Slight Mass (g) 2.00 HCI (vol) 40.0 HCI (N) 0.10 NaOH (N) 0.10 Acid NaOH Equivalent PH (ml) (mq eq/q) 1.7 0.00 2.000 2.0 8.24 1.588 2.5 15.24 1.238 3.0 18.39 1.081 3.5 19.73 1.014 4.0 21.07 0.947 4.5 25.57 0.722 5.0 28.13 0.594 6.0 29.82 0.509 7.0 32.46 0.377 Fizz Rating: none Method: Sobek (alternate fizz rating) Measured NP: 19 kg CaC03/t Sample: 503 WR V 0.500 1.000 1.500 Acid equivalent (mg eq/g) Fizz category used in test Moderate Mass (g) 2.00 HCI (vol) 40.0 HCI (N) 0.50 NaOH (N) 0.61 Acid NaOH Equivalent PH (ml) (mq eq/q) 1.2 0.00 10.000 2.0 26.34 2.019 2.5 26.57 1.949 3.0 26.84 1.667 3.5 27.20 1.758 4.0 28.82 1.268 4.5 29.31 1.119 5.0 29.55 1.046 6.0 30.20 0.849 7.0 30.69 0.701 Fizz Rating: none Method: Sobek (alternate fizz rating) Measured NP: 35 kg CaC03/t 1.500 2.000 Add equivalent (mg eq/g) Sample: 504 WR Fizz category used in test None Mass (g) 2.00 HCI (vol) 20.0 HCI (N) 0.10 NaOH (N) 0.10 Acid NaOH Equivalent PH (ml) (mq eq/g) 1.000 2.0 0.00 1.000 2.5 6.20 0.690 3.0 8.66 0.567 3.5 9.90 0.505 4.0 11.00 0.450 4.5 13.26 0.337 5.0 14.46 0.277 6.0 15.58 0.221 7.0 16.98 0.151 Fizz Rating: none Method: Sobek (alternate fizz rating) Measured NP: 8 kg CaC03/t Sample: 504 WR iiiiiii iiiiiisi iiiiiii lliiiiti ijfllj ijfllj jlpljj 0.500 1.000 1.50 Add equivalent (mg eq/g) Fizz category used in test Slight Mass (g) 2.00 HCI (vol) 40.0 HCI (N) 0.10 NaOH (N) 0.10 Acid NaOH Equivalent PH (ml) (mg eo;g) 1.6 0.00 2.000 2.0 16.39 1.181 2.5 23.44 0 828 3.0 26.45 0.678 3.5 28.03 0.599 4.0 29.26 0.537 4.5 32.51 0.375 5.0 33.93 0.304 6.0 34.96 0.252 7.0 36.23 0.189 Fizz Rating: none Method: Sobek (alternate fizz rating) Measured NP: 9 kg CaC03/t Sample: 504 WR 0.500 1.000 1.500 Add equivalent (mg eq/g) Fizz category used in test Moderate Mass (g) 2.00 HCI (vol) 40.0 HCI(N) 0.50 NaOH (N) 0.61 Acid NaOH Equivalent PH (ml) (mg eq/g) 1.2 0.00 10.000 2.0 28.64 1.322 2.5 29.10 1.183 3.0 29.34 1.110 3.5 29.67 1.010 4.0 30.59 0.731 4.5 30.71 0.695 5.0 30.91 0.634 6.0 31.22 0.540 7.0 31.39 0.489 Fizz Rating: none Method: Sobek (alternate fizz rating) Measured NP: 24 kg CaC03/t 0.500 1.000 1.50 Add equivalent (mg eq/g) ACID BASE ACCOUNTING TEST RESULTS / TITR_9.XLS 07/02/98 Sample: 917 WR Fizz category used in test Slight Mass (g) 2.00 HCI (vol) 40.0 HCI (N) 0.10 NaOH (N) 0.10 Acid NaOH Equivalent PH (ml) (mq eq/q) 2.000 2.0 0.00 2.000 2.5 5.56 1.722 3.0 8.50 1.575 3.5 9.73 1.514 4.0 11.59 1.421 4.5 15.51 1.225 5.0 17.48 1.126 6.0 19.57 1.022 7.0 22.44 0.878 Fizz Rating: moderate Method: Sobek (alternate fizz rating) Measured NP: 44 kg CaC03/t Sample: 917 WR Fizz category used in test Moderate Mass (g) 2.00 HCI (vol) 40.0 HCI (N) 0.50 NaOH (N) 0.50 Acid NaOH Equivalent PH (ml) (mq eq/q) 1.2 0.00 10.000 2.0 25.32 3.670 2.5 26.96 3.260 3.0 27.66 3.085 3.5 28.08 2.980 4.0 28.94 2.765 4.5 32.05 1.988 5.0 33.18 1.705 6.0 33.84 1.540 7.0 34.93 1.268 Fizz Rating: moderate Method: Sobek (alternate fizz rating) Measured NP: 63 kg CaC03/t Sample: 917 WR _ _«-»•_• i.jfju *..Tt.r Add equivalent (mg eq/g) Fizz category used in test Strong Mass (g) 2.00 HCI (vol) 80.0 HCI (N) 0.50 NaOH (N) 0.63 Acid NaOH Equivalent PH (ml) (mq eq/g) 0.9 0.00 20.000 2.0 43.22 6.306 2.5 44.34 5.951 3.0 44.60 5.868 3.5 45.90 5.457 4.0 50.35 4.047 4.5 53.93 2.912 5.0 54.46 2.744 6.0 56.59 2.069 7.0 58.68 1.407 Fizz Rating: moderate Method: Sobek (alternate fizz rating) Measured NP: 70 kg CaC03/t 2.000 3.000 4.000 5.000 6.000 Add equivalent (mg eq/g) Sample: 918 WR Fizz category used in test None Mass (g) 2.00 HCI (vol) 20.0 HCI (N) 0.10 NaOH (N) 0.10 Acid NaOH Equivalent PH (ml) (mq eq/q) 1.000 1.000 2.6 0.00 1.000 3.0 1.68 0.916 3.5 2.74 0.863 4.0 3.45 0.828 4.5 4.81 0.760 5.0 5.94 0.703 6.0 7.13 0.644 7.0 10.26 0.487 Fizz Rating: none Method: Sobek (alternate fizz rating) Measured NP: 24 kg CaC03/t Sample: 918 WR iiiiiiiiii ipiiiififjjlll 1.0* -J*. !->•_ 4-XCI Add equivalent (mg eq/g) Fizz category used in test Slight Mass (g) 2.00 HCI (vol) 40.0 HCI (N) 0.10 NaOH (N) 0.10 Acid NaOH Equivalent PH (ml) (mg eq/g) 1.9 0.00 2.000 2.0 2.53 1.874 2.5 9.46 1.526 3.0 12.36 1.382 3.5 13.61 1.320 4.0 15.45 1.228 4.5 19.63 1.009 5.0 21.41 0.930 6.0 23.27 0.837 7.0 26.92 0.654 Fizz Rating: none Method: Sobek (alternate fizz rating) Measured NP: 33 kg CaC03/t Sample. 918 WR A" 0.UOU -..JUL- _.JX J 000 4.000 5.000 Add equivalent (mg eq/g) Fizz category used in test Moderate Mass (g) 2.00 HCI (vol) 40.0 HCI (N) 0.50 NaOH (N) 0.63 Acid NaOH Equivalent PH (ml) (mg eq/g) 1.5 0.00 10.000 2.0 14.84-5.298 2.5 15.69 5.029 3.0 16.09 4.902 3.5 16.66 4.721 4.0 19.96 3.676 4.5 22.93 2.735 5.0 23.56 2.535 6.0 25.26 1.996 7.0 27.33 1.340 Fizz Rating: none Method: Sobek (alternate fizz rating) Measured NP: 67 kg CaC03/t lil^;M::;:i:i:Mffi!illiilki;; im ISPS liiiiiiiilBiii 2.000 3.000 4.000 5.000 Add equivalent (mg eq/g) Sample: 919 WR Fizz category used in test Slight Mass (g) 2.00 HCI (vol) 40.0 HCI (N) 0.10 NaOH (N) 0.10 Acid NaOH Equivalent PH (ml) (mg eq/g) 2.000 2.2 0.00 2.000 2.5 3.20 1.840 3.0 6.30 1.685 3.5 6.90 1.655 4.0 8.27 1.587 4.5 10.36 1.482 5.0 11.76 1.412 6.0 13.97 1.302 7.0 17.73 1.114 Fizz Rating: moderate Method: Sobek (alternate fizz rating) Measured NP: 56 kg CaC03/t Sample: 919 WR 2.000 3.000 Add equivalent (mg eq/g) Fizz category used in test Moderate Mass (g) 2.00 HCI (vol) 40.0 HCI (N) 0.50 NaOH (N) 0.50 Acid NaOH Equivalent PH (ml) (mq eq/q) 0.9 0.00 10.000 2.0 23.62 4.095 2.5 25.19 3.703 3.0 25.92 3.520 3.5 26.26 3.435 4.0 27.01 3.248 4.5 29.47 2.633 5.0 30.47 2.383 6.0 31.34 2.165 7.0 32.34 1.915 Fizz Rating: moderate Method: Sobek (alternate fizz rating) Measured NP: 96 kg CaC03/t Sample: 919 WR 2.500 3.5O0 Add equivalent (mg eq/g) Fizz category used in test Strong Mass (g) 2.00 HCI (vol) 80.0 HCI (N) 0.50 NaOH (N) 0.50 Acid NaOH Equivalent PH (ml) (mq eq/q) 0.5 0.00 20.000 2.0 60.32 4.920 2.5 62.36 4.410 3.0 63.35 4.163 3.5 63.74 4.065 4.0 64.61 3.848 4.5 67.87 3.033 5.0 69.25 2.688 6.0 70.07 2.483 7.0 70.83 2.293 Fizz Rating: moderate Method: Sobek (alternate fizz rating) Measured NP: 115 kg CaC03/t 3.000 4.000 Acid equivalent (mg eq/g) ACID BASE ACCOUNTING TEST RESULTS / TITR_17.XLS 07/0296 Sample: 923 WR Fizz category used in test None Mass (g) 2.00 HCI (vol) 20.0 HCI (N) 0.10 NaOH (N) 0.10 Acid NaOH Equivalent pH (ml) (mg eq/q) 1.000 1.000 1.000 1.000 1.000 1.000 1.000 5.2 0.00 1.000 6.0 1.46 0.927 7.0 5.40 0.730 Fizz Rating: none Method: Sobek (alternate fizz rating) Measured NP: 37 kg CaC03/t Sample: 923 WR Ptf0 Blips — iiiiibiit iiiisi llljllf — Bill 1.000 2.000 3.000 Acid equivalent (mg eq/g) Fizz category used in test Slight Mass (g) 2.00 HCI (vol) 40.0 HCI (N) 0.10 NaOH (N) 0.10 Acid NaOH Equivalent PH (ml) (mq eq/q) 2.000 2.2 0.00 2.000 2.5 2.92 1.854 3.0 5.62 1.719 3.5 7.16 1.642 4.0 8.93 1.554 4.5 12.40 1.380 5.0 14.83 1.259 6.0 17.60 1.120 7.0 22.41 0.880 Fizz Rating: none Method: Sobek (alternate fizz rating) Measured NP: 44 kg CaC03/t Sample: 923 WR 3 2.000 3.000 * Acid equivalent (mg eq/g) Fizz category used in test Moderate Mass (g) 2.00 HCI (vol) 40.0 HCI (N) 0.50 NaOH (N) 0.63 Acid NaOH Equivalent PH (ml) (mq eq/q) 1.3 0.00 10.000 2.0 13.22 5.811 2.5 13.93 5.586 3.0 14.24 5.488 3.5 14.86 5.292 4.0 17.79 4.363 4.5 20.92 3.371 5.0 21.86 3.074 6.0 24.05 2.380 7.0 26.79 1.512 Fizz Rating: none Method: Sobek (alternate fizz rating) Measured NP: 76 kg CaC03/t 2.000 3.000 4.000 5.000 Acid equivalent (mg eq/g) Sample: 924 WR Fez category used in test None Mass (g) 2.00 HCI (vol) 20.0 HCI (N) 0.10 NaOH (N) 0.10 Acid NaOH Equivalent PH (ml) (mq eq/g) 1.000 1.000 2.5 0.00 1.000 3.0 2.40 0.880 3.5 3.31 0.835 4.0 4.13 0.794 4.5 5.65 0.718 5.0 6.94 0.653 6.0 8.26 0.587 7.0 10.55 0.473 Fizz Rating: none Method: Sobek (alternate fizz rating) Measured NP: 24 kg CaC03/t Sample: 924 WR 5 1.000 2.000 3.000 Acid equivalent (mg eq/g) Fizz category used in test Slight Mass (g) 2.00 HCI (vol) 40.0 HCI (N) 0.10 NaOH (N) 0.10 Acid NaOH Equivalent PH (ml) (mg eq/g) 2.0 0.00 2.000 2.0 1.43 1.929 2.5 8.16 1.592 3.0 10.90 1.455 3.5 12.39 1.381 4.0 14.06 1.297 4.5 18.25 1.088 5.0 20.37 0.982 6.0 21.74 0.913 7.0 25.37 0.732 Fizz Rating: none Method: Sobek (alternate fizz rating) Measured NP: 37 kg CaC03/t Sample: 924 WR 2.000 3.000 Add equivalent (mg eq/g) Fizz category used in test Moderate Mass (g) 2.00 HCI (vol) 40.0 HCI (N) 0.50 NaOH (N) 0.63 Acid NaOH Equivalent PH (ml) (mq eq/q) 1.2 0.00 10.000 2.0 18.84 4.031 2.5 19.73 3.749 3.0 20.05 3.647 3.5 20.32 3.562 4.0 22.56 2.852 4.5 25.03 2.069 5.0 25.33 1.974 6.0 26.65 1.556 7.0 28.41 0.998 Fizz Rating: none Method: Sobek (alternate fizz rating) Measured NP: 50 kg CaC03/t 1.000 2.00T VVr Add equivalent (mg eq/g) Sample: 925 WR Fizz category used in test None Mass (g) 2 00 HCI (vol) 20.0 HCI (N) 0.10 NaOH (N) 0.10 Acid NaOH Equivalent PH (ml) (mq eq/q) 1.000 2.3 0.00 1.000 2.5 2.23 0.689 3.0 4.88 0.756 3.5 6.12 0.694 4.0 7.66 0.617 4.5 10.21 0.490 5.0 11.53 0.424 6.0 13.49 0.326 7.0 14.77 0.262 Fizz Rating: none Method: Sobek (alternate fizz rating) Measured NP: 13 kg CaC03/t Sample: 925 WR 1.000 2.000 3.000 Add equivalent (mg eq/g) Fizz category used in test Slight Mass (g) 2.00 HCI (vol) 40.0 HCI (N) 0.10 NaOH (N) 0.10 Acid NaOH Equivalent PH (ml) (mg eq/g) 1.7 0.00 2.000 2.0 7.46 1.627 2.5 14.52 1.274 3.0 17.23 1.139 3.5 19.07 1.047 4.0 20.59 0.971 4.5 25.60 0.720 5.0 27.81 0.610 6.0 30.00 0.500 7.0 31.74 0.413 Fizz Rating: none Method: Sobek (alternate fizz rating) Measured NP: 21 kg CaC03/t Sample: 925 WR ,000 2.000 3.000 Add equivalent (mg eq/g) Fizz category used in test Moderate Mass (g) 2.00 HCI (vol) 40.0 HCI (N) 0.50 NaOH (N) 0.63 Acid NaOH Equivalent PH (ml) (mq eq/q) 1.2 0.00 10.000 2.0 10.000 2.5 10.000 3.0 16.14 4.886 3.5 16.78 4.683 4.0 19.90 3.695 4.5 23.40 2.586 5.0 23.75 • 2.475 6.0 26.76 1.521 7.0 28.20 1.065 Fizz Rating: none Method: Sobek (alternate fizz rating) Measured NP: 53 kg CaC03/t 2.000 3.000 4.000 Acid equivalent (mg eq/g) ACID BASE ACCOUNTING TEST RESULTS / TITRJ 8.XLS 07/02/98 Sample: 929 WR Fizz category used in test None Mass (g) 2.00 HCI (vol) 20.0 HCI (N) 0.10 NaOH (N) 0.10 Acid NaOH Equivalent PH (ml) (mg eq/g) 1.000 2.3 0.00 1.000 2.5 1.98 0.901 3.0 4.20 0.790 3.5 5.11 0.745 4.0 6.46 0.677 4.5 9.94 0.503 5.0 11.08 0.446 6.0 12.65 0.366 7.0 14.48 0.276 Fizz Rating: none Method: Sobek (alternate fizz rating) Measured NP: 14 kg CaC03/t Sample: 929 WR III11IB iillllll 1.000 2.000 Acid equivalent (mg eq/g) Fizz category used in test Slight Mass (g) 2.00 HCI (vol) 40.0 HCI (N) 0,10 NaOH (N) 0.10 Acid NaOH Equivalent PH (ml) (mq eq/g) 1.8 0.00 2.000 2.0 6.66 1.667 2.5 14.04 1.298 3.0 17.05 1.148 3.5 16.69 1.066 4,0 20.32 0.984 4.5 24.90 0.755 5.0 27.66 0.617 6.0 29.66 0.517 7.0 32.71 0.365 Fizz Rating: none Method: Sobek (alternate fizz rating) Measured NP: 18 kg CaC03/t Sample: 929 WR 2.000 Add equivalent (mg eq/g) Fizz category used in test Moderate Mass (g) 2.00 HCI (vol) 40.0 HCI (N) 0.50 NaOH (N) 0.63 Acid NaOH Equivalent PH (ml) (mq eq/q) 1.2 0.00 10.000 2.0 19.63 3.780 2.5 20.26 3.581 3.0 20.57 3.462 3.5 20.96 3.352 4.0 22.72 2.801 4.5 25.34 1.971 5.0 25.74 1.644 6.0 27.33 1.340 7.0 28.62 0.932 Fizz Rating: none Method: Sobek (alternate fizz rating) Measured NP: 47 kg CaC03/t lllilii ^— 1.500 2.500 3.500 Add equivalent (mg eq/g) Sample: 930 WR Fizz category used in test None Mass (g) 2.00 HCI (vol) 20.0 HCI (N) 0.10 NaOH (N) 0.10 Acid NaOH Equivalent pH (ml) (mq eq/g) 1.000 2.1 0.00 1.000 2.5 4.80 0.760 3.0 7.27 0.637 3.5 8.72 0.564 4.0 9.97 0.502 4.5 12.84 0.358 5.0 14.28 0.2B6 6.0 15.84 0.208 7.0 17.50 0.125 Fizz Rating: none Method: Sobek (alternate fizz rating) Measured NP: 6 kg CaC03/t Sample: 930 WR 1.000 2.000 3.000 Add equivalent (mg eq/g) Fizz category used in test Slight Mass (g) 2.00 HCI (vol) 40.0 HCI(N) 0.10 NaOH (N) 0.10 Acid NaOH Equivalent PH (ml) (mq eq/q) 1.6 0.00 2.000 2.0 11.71 1.415 2.5 19.30 1.035 3.0 21.74 0.913 3.5 23.50 0.625 4,0 25.60 0.720 4,5 29.70 0.515 5.0 32.12 0.394 6.0 34.86 0.257 7.0 36.05 0.198 Fizz Rating: none Method: Sobek (alternate fizz rating) Measured NP: 10 kg CaC03/t Sample: 930 WR 2.000 3.000 Add equivalent (mg eq/g) Fizz category used in test Moderate Mass (g) 2.00 HCI (vol) 40.0 HCI (N) 0.50 NaOH (N) 0.63 Acid NaOH Equivalent PH (ml) (mg eq/g) 1.2 0.00 10.000 2.0 22.27 2.944 2.5 22.99 2.716 3.0 23.35 2.602 3.5 23.66 2.440 4.0 25.02 2.072 4.5 27.35 1.334 5.0 27.95 1.144 6.0 28.86 0.856 7.0 29.83 0.548 Fizz Rating: none Method: Sobek (alternate fizz rating) Measured NP: 27 kg CaC03/t 1.000 2.000 3.000 Add equivalent (mg eq/g) Sample: CCRMP RTS-4 Fizz category used in test None Mass (g) 2.00 HCI (vol) 20.0 HCI (N) 0.10 NaOH (N) 0.10 Acid NaOH Equivalent pH (ml) (mq eq/q) 1.000 1.000 1.000 1.000 1.000 1.000 1.000 1.000 3.8 0.00 1.000 7.0 20.00 0.000 Fizz Rating: none Method: Sobek (alternate fizz rating) Measured NP: 0 kg CaC03/t Sample: CCRMP RTS-4 .000 2.000 3.000 Add equivalent (mg eq/g) Fizz category used in test Slight Mass (g) 2.00 HCI (vol) 40.0 HCI (N) 0.10 NaOH (N) 0.10 Acid NaOH Equivalent pH (ml) (mg eq/g) 2.000 2.000 2.000 2.000 2.000 2.000 2.000 2.000 2.000 7.0 38.82 0.059 Fizz Rating: none Method: Sobek (alternate fizz rating) Measured NP: 3 kg CaC03/t Sample: CCRMP RTS-4 000 2.000 3.000 Add equivalent (mg eq/g) Fizz category used in test Moderate Mass (g) 2.00 HCI (vol) 40.0 HCI (N) 0.50 NaOH (N) 0.50 Acid NaOH Equivalent pH (ml) (mq eq/g) 10.000 10.000 10.000 10.000 10.000 10.000 10.000 10.000 1.7 26.76 3.310 7.0 39.50 0.125 Fizz Rating: none Method: Sobek (alternate fizz rating) Measured NP: 6 kg CaC03/t .000 2.000 3.000 Add equivalent (mg eq/g) ACID BASE ACCOUNTING TEST RESULTS / TITR_19.XLS 07/02/98 Sample: CCRMP CZN-1 Fa2 category used in test None Mass (g) 2.00 HCI (vol) 20.0 HCI(N) 0.10 NaOH (N) 0.10 Acid NaOH Equivalent pH (ml) (mg eq/q) 1.000 1.000 1.000 1.000 1.000 1.000 1.000 1.000 4.0 0.00 1.000 7.0 15.59 0.221 Fizz Rating: none Method: Sobek (alternate fizz rating) Measured NP: 11 kg CaC03/t Sample: CCRMP CZN-1 ii^llllilliP iiiiiiiiiill iiitiiii^ii iiiiii mm 300 2.DO0 3.000 Add equivalent (mg eq/g) Fizz category used in test Slight Mass (g) 2.00 HCI (vol) 40.0 HCI (N) 0.10 NaOH (N) 0.10 Acid NaOH Equivalent PH (ml) (mq eq/q) 2.000 2.000 2.000 2.000 2.000 2.000 2.000 2.000 2.0 0.00 2.000 7.0 36.12 0.194 Fizz Rating: none Method: Sobek (alternate fizz rating) Measured NP: 10 kg CaC03/t Sample. CCRMP CZN-1 1.000 2.000 3.000 Add equivalent (mg eq/g) Fizz category used in test Moderate Mass (g) 2.00 HCI (vol) 40.0 HCI (N) 0.50 NaOH (N) 0.50 Acid NaOH Equivalent pH (ml) (mg eq/g) 10.000 10.000 10.000 10.000 10.000 10.000 10.000 10.000 1.2 0.00 10.000 7.0 37.79 0.553 Fizz Rating: none Method: Sobek (alternate fizz rating) Measured NP: 28 kg CaC03/t 1.000 2.000 3.000 Add equivalent (mg eq/g) Sample: CCRMP KC-1A Fizz category used in test None Mass (g) 2.00 HCI (vol) 20.0 HCI (N) 0.10 NaOH (N) 0.10 Acid NaOH Equivalent pH (ml) (mg eq/g) 1.000 1.000 1.000 1.000 1.000 1.000 1.000 1.000 2.3 0.00 1.000 7,0 16.95 0.153 Fizz Rating: none Method: Sobek (alternate fizz rating) Measured NP: 8 kg CaC03/t Sample: CCRMP KC-IA 000 2 000 3.000 Add equivalent (mg eq/g) Fizz category used in test Slight Mass (g) 2.00 HCI (vol) 40.0 HCI (N) 0.10 NaOH (N) 0.10 Acid NaOH Equivalent pH (ml) (mq eq/g) 2.000 2.000 2.000 2.000 2.000 2.000 2.000 2.000 1.9 0.00 2.000 7.0 37,31 0.135 Fizz Rating: none Method: Sobek (alternate fizz rating) Measured NP: 7 kg CaC03/t Sample: CCRMP KC-IA 1.000 2.000 3.000 Acid equivalent (mg eq/g) Fizz category used In test Moderate Mass (g) 2.00 HCI (vol) 40.0 HCI (N) 0.50 NaOH (N) 0.50 Add NaOH Equivalent pH (ml) (mq eq/g) 10.000 10,000 10.000 10.000 10.000 10.000 10.000 10.000 1.2 0.00 10.000 7.0 38.75 0.313 Fizz Rating: none Method: Sobek (alternate fizz rating) Measured NP: 16 kg CaC03/t 000 2.000 3.000 Add equivalent (mg eq/g) Sample: CCRMP MW-1 Fizz category used in test None Mass (g) 2.00 HCI (vol) 20.0 HCI (N) 0.10 NaOH (N) 0.10 Acid NaOH Equivalent pH (ml) (mq eq/g) 1.000 1.000 1.000 1.000 1.000 1.000 1.000 1.000 2.2 0.00 1.000 7.0 19,41 0.030 Fizz Rating: none Method: Sobek (alternate fizz rating) Measured NP: 1 kg CaC03/t Sample: CCRMP MW-1 000 2.000 3.000 Add equivalent (mg tq/g) Fizz category used in test Slight Mass (g) 2.00 HCI (vol) 40.0 HCI (N) 0.10 NaOH (N) 0.10 Acid NaOH Equivalent pH (ml) (mg eq/q) 2.000 2.000 2.000 2.000 2.000 2.000 2 000 2 000 1.6 0.00 2.000 7.0 38.22 0.089 Fizz Rating: none Method: Sobek (alternate fizz rating) Measured NP: 4 kg CaC03/t Sample: CCRMP MW-1 1,000 2.000 3.000 Add equivalent (mg eq/g) Fizz category used in test Moderate Mass (g) 2.00 HCI (vol) 40.0 HCI (N) 0.50 NaOH (N) 0.50 Acid NaOH Equivalent PH (ml) (mq eq/q) 10.000 10.000 10.000 10.000 10.000 10.000 10.000 10.000 1.2 0.00 10.000 7.0 39,14 0.215 Fizz Rating: none Method: Sobek (alternate fizz rating) Measured NP: 11 kg CaC03/t .000 2.000 3.000 Add equivalent <mg eq/g) ACID BASE ACCOUNTING TEST RESULTS / TITR_20.XLS 07/02/98 

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