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Hydrolysis of aluminum sulphate solutions at high temperatures Nikolic, Cvetko 1971-12-31

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HYDROLYSIS OF ALUMINUM SULPHATE SOLUTIONS AT HIGH TEMPERATURES  BY  CVETKO NIKOLIC D i p l . Ing. (Chemical E n g i n e e r i n g ) U n i v e r s i t y of B e l g r a d e , 1963  A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF APPLIED SCIENCE  In the Department of METALLURGY  We accept t h i s t h e s i s as conforming t o the required  THE  standard  UNIVERSITY OF BRITISH COLUMBIA February  1971  In p r e s e n t i n g an  this thesis  in p a r t i a l  advanced degree at the U n i v e r s i t y  the  Library  shall  f o r s c h o l a r l y purposes may representatives.  be g r a n t e d by  his  of  t h i s t h e s i s f o r f i n a n c i a l gain  A p r i l 28,  Metallurgy  1971  for  requirements f o r  Columbia, reference  the Head o f my  It i s understood  permission.  The U n i v e r s i t y o f B r i t i s h Vancouver 8, Canada  Date  British  the  Columbia  shall  that  not  be  I agree and  for e x t e n s i v e copying of  by  Department of  of  make i t f r e e l y a v a i l a b l e  I f u r t h e r agree t h a t p e r m i s s i o n  written  f u l f i l m e n t of  that  study.  this thesis Department  copying o r  or  publication  allowed without  my  - ii ABSTRACT  Normal and acid aluminum sulphate solutions containing about 6.0 gr/1 of aluminum and up to 50 gr/1 SO^ were hydrolyzed u n t i l equilibrium was reached i n the temperature  region 125-250°C.  Under  the equilibrium conditions the only stable s o l i d phase observed i n equilibrium with a l i q u i d phase of various compositions was basic aluminum sulphate with nominal  formula 3A1 0 .4S0 .9E^0. 2  3  3  A  small portion of the ternary diagrams for the system A^O^-SO^-K^Q at 225°C and 250°C was constructed.  A mixture of aluminum sulphate  and other metal sulphates, K„S0., Na S0,, Li.SO., FeSO. and CuSO. 2 4 2 4 2 4 4 4 o  i . e . was hydrolyzed at 225°C i n order to find the e f f e c t of these s a l t s on hydrolysis. The o v e r a l l hydrolysis reaction was found to occur according to the chemical equation;  ekl^  + 4HS0. 4  + 14H„0 2  • 3Al 0 .4S0„.9H 0 + 14H 2 3 3 2 o  o  +  o  The equilibrium constants at 125, 150, 175, 200, 225 and 250°C were determined. F i n a l l y a mechanism for the hydrolysis of aluminum sulphate was proposed.  - iii  -  ACKNOWLEDGEMENT  The author wishes his continuing extended  to express s i n c e r e thanks to Dr. E. P e t e r s f o r  guidance and i n t e r e s t i n t h i s p r o j e c t .  H i s thanks i s  to f e l l o w graduate s t u d e n t s , p a r t i c u l a r l y Mr. D. Jones and t h e  t e c h n i c a l s t a f f o f the Department o f M e t a l l u r g y f o r t h e i r h e l p f u l discussions  and a s s i s t a n c e .  F i n a n c i a l support from t h e N a t i o n a l Research C o u n c i l o f Canada i n the form o f a Research A s s i s t a n t s h i p i s g r a t e f u l l y  acknowledged.  - iv -  TABLE OF CONTENTS Page  1.  INTRODUCTION  2.  A REVIEW OF THE LITERATURE  3.  4.  1 .. .  3  2.1  The F e 0 - S 0 - H 0 System  3  2.2  The A 1 0 ~ S 0 - H 0 System  6  2.3  The M 0 - A 1 0 - S 0 - H 0 System  2  2  2  3  3  3  3  2  3  2  2  3  2  10  EXPERIMENTAL  12  3.1  E x p e r i m e n t a l Technique  12  3.2  M a t e r i a l s Used  18  3.3  Preparation  21  3.4  Chemical A n a l y s i s  RESULTS AND 4.1  of Solutions f o r Hydrolysis  DISCUSSION  22 24  The E f f e c t of Temperature on H y d r o l y s i s of Aluminum Sulphate S o l u t i o n s 4.1.1  H y d r o l y s i s of Aluminum Sulphate S o l u t i o n s at 125°C  4.1.2  30  H y d r o l y s i s of Aluminum Sulphate S o l u t i o n s at 200°C  4.1.5  28  H y d r o l y s i s o f Aluminum Sulphate S o l u t i o n s at 175°C  4.1.4  25  H y d r o l y s i s o f Aluminum Sulphate S o l u t i o n s at 150°C  4.1.3  25  32  H y d r o l y s i s of Aluminum Sulphate S o l u t i o n s at 225°C  34  - V -  Page  4.1.6  H y d r o l y s i s of Aluminum S u l p h a t e S o l u t i o n s a t 250°C  4.2  The E f f e c t  36  of S u l p h u r i c A c i d C o n c e n t r a t i o n on  H y d r o l y s i s of Aluminum Sulphate S o l u t i o n s 4.2.1  H y d r o l y s i s of Aluminum Sulphate S o l u t i o n s with I n i t i a l  4.2.2  38  S0 :A1 0 3  2  3  R a t i o > 3.0 a t 2 5 0 ° C .  H y d r o l y s i s o f Aluminum Sulphate S o l u t i o n s with I n i t i a l  S O ^ A l ^  R a t i o > 3.0 a t 225°C...  4.3  The E q u i l i b r i u m Constants  4.4  Ternary Diagrams f o r the System A 1 0 - S 0 - H 0  4.5  Mechanism of the H y d r o l y s i s of Aluminum Sulphate  4.6  The E f f e c t  of A l k a l i  3  3  .  51  ...  55  2  M e t a l Sulphates on H y d r o l y s i s  of Aluminum Sulphate a t 225°C The E f f e c t  56  of L i t h i u m Sulphate on H y d r o l y s i s  of Aluminum Sulphate a t 225°C 4.6.2  The E f f e c t  of Potassium  The E f f e c t  The E f f e c t  65  of Copper Sulphate on H y d r o l y s i s  of Aluminum Sulphate S o l u t i o n s a t 225°C 4.7.2  61  of D i v a l e n t M e t a l Sulphates on H y d r o l y s i s  of Aluminum Sulphate S o l u t i o n s a t 225°C 4.7.1  60  Sulphate on H y d r o l y s i s  of Aluminum Sulphate a t 225°C 4.7  58  The E f f e c t o f Sodium Sulphate on H y d r o l y s i s of Aluminum Sulphate a t 225°C  4.6.3  40 42  2  4.6.1  38  67  The E f f e c t o f F e r r o u s Sulphate on H y d r o l y s i s of Aluminum Sulphate S o l u t i o n s a t 225°C  69  - vi -  Page 4.8 5.  A p p l i c a t i o n o f the H y d r o l y s i s  CONCLUSIONS  Process  .  71 74  APPENDIX I  SOLUBILITY OF ALUMINUM SULPHATE  75  APPENDIX I I  ANALYSIS OF THE SOLID PHASE  76  APPENDIX I I I  X-RAY DIFFRACTION PATTERNS  77  LITERATURE  81  - vii LIST OF TABLES Table  Page  1  Hydrolysis of aluminum sulphate solutions at 125°C...  26  2  Hydrolysis of aluminum sulphate solutions at 150°C...  28  3  Hydrolysis of aluminum sulphate solutions at 175°C...  30  4  Hydrolysis of aluminum sulphate solutions at 200°C...  32  5  Hydrolysis of aluminum sulphate solutions at 225°C...  34  6  Hydrolysis of aluminum sulphate solutions at 250°C...  36  7  The effect of excess sulphuric acid on hydrolysis of aluminum sulphate at 250°C  8  40  The effect of excess sulphuric acid on hydrolysis of aluminum sulphate at 225°C  9  42  Equilibrium constant f o r the reaction HSO^  J H  +  +  S u  ^T •  10  Hydrolysis  constant of water  11  Equilibrium hydrolysis of normal aluminum sulphate i n  46  the temperature range 125-250°C 12  45  ^7  Equilibrium constants for hydrolysis of aluminum sulphate solutions with excess sulphuric acid at 225°C and 250°C  13  47  Equilibrium constants for the hydrolysis reaction of aluminum sulphate  49  14  Solution.composition  of 250°C  51  15  Solution composition at 225°C  52  16  Equilibrium constants for reaction A l AKOH)^ " •+ H 4  +  I | | + ^0  £ 56 l  - viii -  Table 17  Page Hydrolysis of aluminum sulphate-lithium sulphate solution at 225°C  18  58  Hydrolysis of aluminum sulphate-sodium sulphate solution at 225°C  6  1  solution at 225°C  6  3  20  Ionic r a d i i of the ions involved i n the system  65  21  Hydrolysis of aluminum sulphate-copper sulphate  19  Hydrolysis of aluminum sulphate-potassium  sulphate  solution at 225°C 22  6 7  Hydrolysis of aluminum sulphate-ferrous  sulphate  solution at 225°C I-A  S o l u b i l i t y of A l ( S 0 . ) o  2 I-B  6 9  o  i n water  75  43  S o l u b i l i t y of aluminum sulphate i n aqueous solutions of sulphuric acid at 25°C  75  I-C  S o l u b i l i t y of aluminum sulphate i n aqueous 10% ^SO^.  75  II  Analysis of the s o l i d phases  76  III-A  D i f f r a c t i o n pattern of the p r e c i p i t a t e obtained at 150°C  III-B  X-Ray d i f f r a c t i o n pattern  77 of the p r e c i p i t a t e obtained  at 175°C III-C  X-Ray d i f f r a c t i o n pattern of the p r e c i p i t a t e obtained at 200°C  III-D  78  X-Ray d i f f r a c t i o n pattern of the p r e c i p i t a t e obtained at 225°C  III-E  77  78  X-Ray d i f f r a c t i o n pattern of the p r e c i p i t a t e obtained at 250°C  79  - ix Table III-F  Page X-Ray d i f f r a c t i o n pattern of the p r e c i p i t a t e obtained from FeSO.-Al-CSO.K solution at 225°C  4 III-G  2  43  X-Ray d i f f r a c t i o n pattern of potassium alunite obtained at 225°C  II1-H  80  X-Ray d i f f r a c t i o n pattern of sodium alunite obtained at 225°C  III-I  79  80  X-Ray d i f f r a c t i o n pattern of lithium alunite obtained at 225°C  80  - X  -  LIST OF FIGURES Figure  Page  1  F e 0 - S 0 - H 0 system a t 200°C  2  F e 0 - S 0 - H 0 system at 140°C  .3  A 1 0 - S 0 - H 0 system at 220°C  2  2  2  3  3  3  3  3  3  4  2  '  2  5 7  2  4  E x p e r i m e n t a l Apparatus  13  5  YSI-602 T e r m i s t o r C a l i b r a t i o n  14  6  Transducer  1.5  7  P r e s s u r e Dependence  8  H e a t i n g Time to Reach the Working Temperature  17  9  Hydrolysis  of Aluminum Sulphate at 125°C  27  10  H y d r o l y s i s o f Aluminum Sulphate at 150°C  29  11  H y d r o l y s i s of Aluminum Sulphate at 175°C  31  12  H y d r o l y s i s of Aluminum Sulphate at 200°C  33  13  H y d r o l y s i s of Aluminum Sulphate a t 225°C  35  14  H y d r o l y s i s o f Aluminum Sulphate at 250°C  37  15  H y d r o l y s i s of A c i d Aluminum Sulphate a t 250°C  39  16  H y d r o l y s i s of A c i d Aluminum Sulphate at 225°C  41  17  Phase Diagram o f the A l ^ - S O ^ H  43  18  Equilibrium Hydrolysis  48  19  The Change of E q u i l i b r i u m Constant w i t h Temperature ..  50  20  A 1 0 - S 0 ~ H 0 System at 250°C  53  21  A 1 0 - S 0 - H 0 System at 225°C  54  22  H y d r o l y s i s of Lithium-Aluminum Sulphate S o l u t i o n a t  23  2  2  3  3  3  3  Calibration on Temperature  0 System  2  2  16  225°C  59  H y d r o l y s i s of Sodium-Aluminum Sulphate S o l u t i o n a t 225°C  62  - xi Figure 24  Page Hydrolysis of Potassium-Aluminum Sulphate Solution at 225°C  64  25  Hydrolysis Yields Dependence on Ionic Radii  66  26  Hydrolysis of Copper-Aluminum Sulphate Solutions at 225°C  27  68  Hydrolysis of Iron-Aluminum Sulphate Solutions at 225°C  28  70  D.T.A. of 3Al 0 .4SO .9H O 2  3  3  2  72  1.  The  aluminum i n d u s t r y was the f i r s t  m e t a l l u r g i c a l process  separated.  and  t o use a p r e s s u r e  hydro-  (The Bayer p r o c e s s ) on a l a r g e s c a l e .  soda s o l u t i o n s a r e used is  INTRODUCTION  to d i s s o l v e aluminum from b a u x i t e s and alumina  Even though c a u s t i c s o l u t i o n s a r e not v e r y  selective  the Bayer p r o c e s s i s l i m i t e d t o low s i l i c a o r e s , alumina  commerically  Caustic  o n l y by t-his p r o c e s s .  i s produced  T h i s has imposed on the aluminum  i n d u s t r y the t a s k o f t r a n s p o r t a t i o n o f b a u x t i e s over a l o n g d i s t a n c e because the p r o d u c i n g  c o u n t r i e s do n o t have b a u x i t e s o f t h e i r own.  The p r o d u c t i o n o f aluminum i n c o u n t r i e s such as Canada and the U n i t e d S t a t e s i s today v e r y s e n s i t i v e t o the a v a i l a b i l i t y of b a u x i t e s from f o r e i g n c o u n t r i e s . With a d e s i r e to r e c o v e r aluminum from c l a y m i n e r a l s , p r o c e s s e s have been c o n s i d e r e d , f r o m  time  to time, t h a t a r e a p p l i c a b l e t o common  North American c l a y s f o r the domestic  p r o d u c t i o n of alumina.  p r o c e s s e s might a l s o be u s e f u l i n the treatment from  copper  o f c e r t a i n mine waters  dump l e a c h i n g , which c o n t a i n d i s s o l v e d aluminum s u l p h a t e , among  other sulphate Any  Such  salts.  new p r o c e s s p r o d u c i n g alumina must compete i n p r i c e w i t h the  Bayer p r o c e s s .  T h i s l i m i t s new l e a c h i n g p r o c e s s e s  S u l p h u r i c a c i d i s the f a v o u r i t e reagent  to cheap r e a g e n t s .  considered f o r alternate  - 2 -  alumina production  processes and an acid process developed by C.S.I.R.O.  *  has been found to produce aluminum sulphate solutions which can be hydrolysed to y i e l d basic aluminum  sulphate.  Most of the work i n hydrolysis has been done with basic aluminum sulphate solutions, or solutions containing a l k a l i and under "process conditions".  metal sulphates  Because of t h i s there i s p r a c t i c a l l y  no data on equilibrium hydrolysis available i n the l i t e r a t u r e . Some equilibrium hydrolysis work was carried out on the Fe^O^-SO^-H^O system.  With some exceptions A^O^-SO^-H^O and Fe20.j-S0 -H20 systems 3  p r e c i p i t a t e similar compounds during hydrolysis. The separation of basic aluminum sulphate s a l t s from aluminum sulphate solutions i s not well understood either from a k i n e t i c or thermodynamic point of view.  This work i s concerned with hydrolysis  reactions of aluminum sulphate solutions that occur i n the temperature range 125-250°C, and attempts were made to study both p r e c i p i t a t i o n rates and the f i n a l e q u i l i b r i a .  Commonwealth S c i e n t i f i c and I n d u s t r i a l Research Organization Melbourne  - 3 -  2. A REVIEW OF THE LITERATURE It i s generally known that above a temperature which i s a c h a r a c t e r i s t i c of the metal ion involved, a sulphate  s a l t becomes less  soluble as the temperature i s further increased. E.T.  Carlson and C.S. Simons"^ have reported the necessity of  temperature increase from 200 to 275°C to achieve s e l e c t i v e extraction of n i c k e l and cobalt from l a t e r i t e ore.  At 200°C,even though n i c k e l and  cobalt sulphate s o l u b i l i t y was high enough to give good recoveries, the s e l e c t i v i t y was rather poor because of the high s o l u b i l i t y of aluminum and iron sulphates.  They noticed that the SO^tA^O^ r a t i o  i n the residue was about 1:1 and suggested that Al^O^ and SO^ e x i s t in i t as a compound.  2.1  The Fe 0 -S0 -H 0 System 2  3  3  2  At elevated temperatures f e r r i c sulphate solutions hydrolyze to 2 p r e c i p i t a t e f e r r i c oxide or basic s a l t s .  Posnjak and Merwin  studied the Fe^^-SO^-H^O system at temperatures up to 200°C.  have At  200°C only three s o l i d phases exist i n equilibrium with various compositions of the l i q u i d phase.  ¥e^0^ i s i n equilibrium with d i l u t e  solutions of f e r r i c sulphate.  The stable phase i n equilibrium with a  somewhat higher ^concentration  of sulphuric acid i n solution i s a basic  s a l t of the composition Fe„0„.2S0_.H 0. o  F i n a l l y , at high  concentrations  2°3~ 3" AT 2 0 0 C° F e  S 0  H  2°  SYSTEM  - 5 -  Fe 03 2  F i q . 2 • Fe 03- S 0 2  AT  3  !40C°  H 0 2  SYSTEM  - 6 -  of s u l p h u r i c acid i n s o l u t i o n the s t a b l e phase i s the normal s a l t , Fe 0 .3S0 2  3  ( F i g . 1).  3  With decreasing temperature  the isotherms become more complicated  and at 140°C, there are f i v e s o l i d phases i n e q u i l i b r i u m with d i f f e r e n t compositions of the l i q u i d phase ( F i g . 2). With f u r t h e r decrease i n temperature  the e q u i l i b r i u m isotherms become s t i l l more complicated.  At 130°C, f e r r i c oxide monohydrate replaces the anhydrous f e r r i c oxide, and at 110°C anhydrous f e r r i c sulphate disappears, and two acid s a l t s are s t a b l e ( F e ^ . 4 S 0 3H 0 and F e ^ . 4S0 .9H 0) . 3>  2.2  2  3  2  The A1 0 -S0 -H 0 System 2  3  3  2  3 P.T. Davey and T.R. Scott  have studied the A^C^-SC^-H^O system  under process conditions i n order to determine the optimum conditions for production of alumina. to varying degrees.  Their experiments approached e q u i l i b r i u m  Solutions with i n i t i a l S 0 : A 1 0 3  2  3  r a t i o l e s s than  3.0 and high i n aluminum content were hydrolyzed at temperatures of 100-220°C.  In t h i s temperature range the only s t a b l e phase observed,  i n e q u i l i b r i u m with various l i q u i d phases, was basic aluminum sulphate of the nominal  formula 3A1 0 «4S0 9H 0. 2  3  3>  2  At these  temperatures,  the p r e c i p i t a t e d phase was i n e q u i l i b r i u m w i t h acid s o l u t i o n s of aluminum' sulphate. for  Only a l i m i t e d number of experiments were performed  periods of time long enough to reach the e q u i l i b r i u m . The  e q u i l i b r i u m s a t u r a t i o n curve f o r t h i s system at 220°C i s given i n F i g . 3.  This s a t u r a t i o n curve was obtained by hydrolyzing aluminum sulphate  s o l u t i o n s with i n i t i a l S0„:A1„0„ r a t i o less than 3.0.  - 8 Basset at  this  temperature  crystallized or  and Goodwin  4  have s t u d i e d t h e system A l ^ - S C ^ - t ^ O  a t 25°C  c o n c e n t r a t e d s o l u t i o n s o f aluminum s u l p h a t e can be  to y i e l d  e i t h e r hydrated  aluminum s u l p h a t e A ^ (SO^) ^. 1 6 ^ 0  the b a s i c s a l t A l 2 O 2 . 2 S O 2 . H H 2 O depending on S O ^ i A ^ O ^ r a t i o o f the  initial  solution.  These c r y s t a l l i n e m a t e r i a l s tend t o o c c l u d e mother-  l i q u o r and a r e r e a d i l y s o l u b l e i n water, which makes i t d i f f i c u l t to remove i m p u r i t i e s by washing w i t h o u t of  the s o l i d  redissolving  a s u b s t a n t i a l amount  phase. 5-9  T.R. S c o t t e t a l . of  have proposed  aluminum from ores low i n b a u x i t e content  stages of the new p r o c e s s a. is  an a c i d p r o c e s s  used b.  f o r recovery  and h i g h i n s i l i c a .  The  a r e d e s c r i b e d as f o l l o w s :  D i g e s t i o n Recycled l i q u o r  c o n t a i n i n g aluminum s u l p h a t e  t o r e c o v e r e x t r a aluminum from an o r e a t 180°C. Modification  A liquor  from  the d i g e s t i o n stage i s t r e a t e d w i t h  f r e s h b a u x i t e to g i v e a s o l u t i o n o f b a s i c aluminum s u l p h a t e w i t h S O ^ A ^ O ^ r a t i o l e s s than 3 . 0 . c. reduce d.  Reduction  Modified l i q u o r i s t r e a t e d with sulphur dioxide to  s o l u b l e i r o n t o the f e r r o u s s t a t e a t 100°C. Hydrolysis  Reduced l i q u o r  i s h y d r o l y z e d a t 220°C i n the  absence o f oxygen to produce b a s i c aluminum.sulphate. e. in  Calcination  B a s i c aluminum s u l p h a t e i s h e a t e d ,  stages a t 1200 °C-1300°C, t o y i e l d  mixture  o f sulphurous  preferrably  the r e q u i r e d a-alumina and a  gases f o r r e c y c l i n g .  J.L. Henry, and G.B. K i n g " ^ have s t u d i e d t h e system A^O^-SO^-E^O  - 9 -  at 60°C.  A t t h i s temperature two b a s i c s a l t s were found  e q u i l i b r i u m w i t h s o l u t i o n s o f aluminum s u l p h a t e having r a t i o v e r y c l o s e t o 3.0.  The s a l t Al^O^.2S0.J.HH^O  w i t h s o l u t i o n s o f pH about 2.5 and A^O^. w i t h s o l u t i o n s o f pH 2 . 5 - 3 . 2 0 .  SO^. 61^0  t o be i n  an S O ^ A ^ O ^  i s i n equilibrium i s i n equilibrium  A t v e r y low c o n c e n t r a t i o n s o f f r e e  s u l p h u r i c a c i d i n s o l u t i o n normal aluminum s u l p h a t e i s the s t a b l e phase a t 60°C. R.A. Chaves, V.V. K a v e l i n reactions  occurring  n i c k e l and c o b a l t of the f o l l o w i n g aluminochromite  and B.P. Sobolev"'"^ have s t u d i e d  i n the s u l p h u r i c a c i d process  from Cuban l a t e r i t e s compounds:  hematite  the side  for extracting  and have r e v e a l e d the presence a-Fe^O^,  boehmite y-A^O^.H^O,  F e C C r A l ^ O ^ , b a s i c i r o n s u l p h a t e Fe^O^. 2 S O . J . H 2 O ,  basic aluminum s u l p h a t e  3 A I 2 O . J . ASO^. 9 ^ 0 and h y d r o n i o j a r o s i t e 3Fe20 .4S0.j. 3  9H 0. 2  The  l a r g e s t amount o f b a s i c aluminum s u l p h a t e i s formed i n the  a u t o c l a v e where the preheated sulphuric  p u l p a t 250°C mixes w i t h  concentrated  a c i d , i n d i c a t i n g very high r e a c t i o n rate at t h i s  Beside  aluminum and f e r r i c  temperature.  s u l p h a t e s a l t s , o t h e r t r i v a l e n t and 12  q u a d r i v a l e n t metal  s u l p h a t e s can be h y d r o l y z e d .  At room temperature  v i o l e t - c o l o u r e d chromium s u l p h a t e s o l u t i o n s a r e s t a b l e , but a t h i g h temperatures these a r e c o n v e r t e d  i n t o green  When S O ^ i C ^ O ^ r a t i o i n the i n i t i a l  complexes i n s o l u t i o n .  s o l u t i o n i s l e s s than  3.0 h y d r o l y z e d  chromic o x i d e i s p r e c i p i t a t e d b u t o n l y at temperatures h i g h e r  than  180°C. Even a t h i g h temperatures s o l u t i o n s o f lanthanum h y d r o l y z e r e a d i l y below pH 7.  s u l p h a t e do not  - 10 Vanadium i s almost  c o m p l e t e l y p r e c i p i t a t e d even i n t h e presence  of f r e e s u l p h u r i c a c i d t o y i e l d ^O,..  I n t h e absence o f oxygen a t  100°C, t h e s o l u t i o n s a r e s t a b l e , b u t p r e c i p i t a t e V^O^ a t above  temperatures  200°C. Scandium c o u l d be s e p a r a t e d from r a r e e a r t h s p r o v i d e d t h a t t h e  s o l u b i l i t y product o f t h e scandium compound was exceeded a t t h e temperature  and i n t h e s o l u t i o n s used.  Indium can be s e p a r a t e d from z i n c e l e c t r o l y s i s l i q u o r s under t h e same c o n d i t i o n s as f o r scandium. T i t a n i u m and z i r c o n i u m s u l p h a t e s h y d r o l y z e r e a d i l y w i t h o u t  recourse  to a u t o c l a v e c o n d i t i o n s .  2.3  The M ^ A ^ O  -SOy-H^O System*  Under o t h e r w i s e t h e same c o n d i t i o n s , t h e presence  of a l k a l i  m e t a l s u l p h a t e s w i l l i n c r e a s e t h e h y d r o l y s i s y i e l d o f a b a s i c s a l t from aluminum s u l p h a t e s o l u t i o n s .  V.S. S a z h i n , A.K. Z a p o l s k i i and N.N.  13 Zaklarova  have s t u d i e d t h e i n f l u e n c e of ammonium, sodium, and  potassium  s u l p h a t e s on h y d r o l y s i s o f aluminum s u l p h a t e s o l u t i o n s .  degree o f h y d r o l y s i s was i n c r e a s e d i n t h e f o l l o w i n g s e r i e s : Na.SO. < K S 0 . . 2 4 2 4  The  (NH^^SO^ <  o  14  S. B r e t s z n a j d e r , J . B o c z a r , J . P i s k o r s k i and J . P o r o w s k i have s t u d i e d t h e h y d r o l y s i s o f aluminum s u l p h a t e s o l u t i o n s w i t h a d d i t i o n of sodium h y d r o x i d e a t 179-285°C f o r 0-240 min. phase was found t o be N a 0 . 3 A 1 0 . 4 S 0 7 H 0 . 2  *  2  3  3>  M 0 = a l k a l i o x i d e ; M = L i , Na, K, NH^ 2  2  The p r e c i p i t a t e d  Excess  solid  sodium h y d r o x i d e  - 11 -  g r e a t l y i n c r e a s e d the y i e l d .  H i g h e r temperature and more d i l u t e  s o l u t i o n s gave h i g h e r y i e l d s .  There was  little  change i n y i e l d f o r  p e r i o d s l o n g e r than 30 min. 15—18 A.K.  Z a p o l s k i i et a l .  from 0-167.5 gr/£ K^SO^  s t u d i e d the e f f e c t of p o t a s s i u m s u l p h a t e  on h y d r o l y s i s o f aluminum s u l p h a t e s o l u t i o n  c o n t a i n i n g 308 gr/£ A l ^ S O ^  a t 170-250°C.  The degree o f h y d r o l y s i s  s h a r p l y i n c r e a s e d at a l l temperatures f o r K^SO^ F u r t h e r i n c r e a s e i n K^SO^  mole/1.  c o n s t a n t c o m p o s i t i o n (3kl^0^. K [A1 (S0 ) (0H) ]' 2  6  4  c o n c e n t r a t i o n had l i t t l e  In the absence of K^SO^  on h y d r o l y s i s .  4  was  >  1 2  c o n c e n t r a t i o n from  0-1  influence  b a s i c aluminum s u l p h a t e s o f  ^SO^. 7 ^ 0 )  were formed.  Potassium a l u n i t e  p r e f e r e n t i a l l y formed at 230-250°C  from  s o l u t i o n s c o n t a i n i n g 1 mole of K^SO^, or more, per mole of A ^ C S O ^ ) ^ At  temperatures 170-190°C  observed.  a less basic s a l t S^SO^.3A1 0 .4S0 9H 0 2  The system N a 0 - A 1 Q - S 0 - H 0 was 2  2  3  3  2  3  3  s t u d i e d a t 200°C  2  was  under  process c o n d i t i o n s i n o r d e r to determine the c o n d i t i o n s f o r r e c o v e r y  19 of  alumina from o r e s .  The p r e c i p i t a t e d compound was  a f o r m u l a v e r y c l o s e to N a 0 . 3 A 1 0 > 4 S 0 . 6 H 0 . 2  K [A1 (S0 ) (0H) 2  6  4  4  1 2  ]  2  3  3  2  = K 0.3A1 0 .4S0 .6H 0. 2  2  3  3  2  found to have  - 12  3.  3.1  Experimental A shaking  EXPERIMENTAL  Technique  autoclave  h y d r o l y s i s experiments.  ( F i g . 4) made o f z i r c o n i u m was  used f o r a l l  The  aluminum  block containing f i v e heaters distribution.  The  -  a u t o c l a v e was ( 1 0 0 W.  t e m p e r a t u r e was  placed  i n an  each) to p r o v i d e  c o n t r o l l e d by  temp" t e m p e r a t u r e c o n t r o l l e r to w i t h i n ± 6.1  °C.  good h e a t  a 71 m o d e l  The  "Thermis-  temperature  c o n t r o l l e r was  u s e d w i t h a Y S 1 - 6 0 2 s e n s i n g p r o b e w i t h a r a n g e o f 80  250°C, and  independently  was  calibrated  against a precision  thermometer i n o i l f o r each temperature used. is  shown i n F i g .  For  by  f o r the  r e g i o n the pressure  a transducer  the h i g h pressure  curve  and  recorded  The  i n the system  g a u g e was The  curve  t h e a u t o c l a v e was  c c o f gas  filled  volume i n the  was  servo-recorder. used.  A  calibration  v a r i a t i o n of  heating time v a r i e d  t h i s v a r i a t i o n i s shown i n F i g .  each r u n ,  l e a v i n g a b o u t 30  calibration  a "Heath"  i s shown i n F i g . 6.  w i t h t e m p e r a t u r e i s g i v e n i n F i g . 7.  For  by  region, a pressure  transducer  t e m p e r a t u r e and  mercury  5.  I n the low p r e s s u r e monitored  The  to  pressure with  8.  w i t h 75 m l  autoclave.  of  solution  J ? temperature controler I  re c o r d e r  tronsduc er  c ooIe r  aotoclov e  Fig. 4- EXPERIMENTAL APAR AT US  sampling tube  - 16 -  •00  150  200  250  Fjg. 8. HEATING TIME TO .REACH THE TEMPERATURE  C°  - 18 Samples o f h y d r o l y z e d s o l u t i o n were taken from the c o o l i n g system and the sampling minutes depending on  time x^as between 2 and 3  temperature.  To make sure  that the samples r e p r e s e n t e d t h e s o l u t i o n from the a u t o c l a v e , the first  3 ml o f s o l u t i o n from the sampling  tube were d i s c a r d e d .  Immediately a f t e r the sample was taken i t was f i l t e r e d and i t s pH measured.  Most o f the h y d r o l y s i s product was p r e c i p i t a t e d on the  a u t o c l a v e w a l l s and remained i n s i d e a f t e r the l i q u i d was removed. The  a u t o c l a v e was then c o o l e d w i t h r u n n i n g water t o room  and  opened.  temperature  The p r e c i p i t a t e was removed from the a u t o c l a v e w a l l s m e c h a n i c a l l y by shaking the a u t o c l a v e w i t h g l a s s b a l l s and a few m i l l i l i t e r s o f d i s t i l l e d water.  A f t e r b e i n g f i l t e r e d and washed, the p r e c i p i t a t e  was d r i e d f o r 24 h r s a t 105°C. A f t e r the s o l i d phase was removed the a u t o c l a v e was washed w i t h sodium hydroxide  s o l u t i o n and then s u c c e s s i v e l y w i t h d i l u t e s u l p h u r i c  a c i d and water. To evaporate and a g a i n allowed  3.2  the r e s i d u a l water, i t was then  to c o o l to room  temperature.  M a t e r i a l s Used Aluminum s u l p h a t e , c r y s t a l , r e a g e n t , Al  ( S 0 ) .18H 0; M.W. 4  666.45  2  Maximum L i m i t o f I m p u r i t i e s Insoluble Free a c i d  0.005% (H SO.)  0.20%  Chloride (Cl)  0.002%  A r s e n i c (As)  0.00005%  B&A,  heated  - 19 -  Heavy metals  (as Pb) 0.001%  I r o n (Fe)  0.002%  Substances not p r e c i p i t a t e d by NH^OH as s u l p h a t e s 0.20%  Lithium  sulphate,  granular  Li S0..H.O 2 4 2  M.W.  o  reagent B & A  127.96  Maximum L i m i t of I m p u r i t i e s Insoluble Chloride Nitrate  0.010% (Cl)  (N0 )  0.001%  3  Heavy m e t a l Iron  0.002%  (as Pb)  (Fe)  Potassium Sodium  0.0002% (K)  0.05%  (Na)  0.10%  Potassium s u l p h a t e , K.S0.. 2 4  M.W.  Maximum L i m i t  0.0005%  c r y s t a l , reagent B & A  174.27  of Impurities  Insoluble  0.005%  Chloride (Cl)  0.001%  Nitrogen (as N)  0.005%  Compounds  A r s e n i c (As)  0.00005%  C a l c i u m , Magnesium and R 0 p r e c i p i t a t e 0.020% 3  Heavy metals  (as Pb) 0.'0005%  I r o n (Fe)  0.0002%  Sodium (Na)  0.005%  - 20 -  Sodium s u l p h a t e , Na„S0. z 4  anhydrous, g r a n u l a r  M.W.  reagent B & A  142.05  Maximum L i m i t of I m p u r i t i e s Insoluble  0.010%  Loss on i g n i t i o n  0.50%  Chloride  (Cl)  0.002%  Nitrogen  compounds  as  (N)  0.0005%  Arsenic  (As)  0.0001%  Calcium, magnesium and  R 0  p r e c i p i t a t e 0.010%  3  Heavy metals I r o n (Fe) Ferrous s u l p h a t e ,  (as Pb) 0.0005% 0.0005% c r y s t a l , reagent B & A  FeSO..7H 0 4 2  M.W.  o  Maximum L i m i t  278.03  of Impurities  Insoluble  0.005%  Chloride (Cl)  0.001%  Phosphate (PO^)  0.001%  Copper (Cu)  0.005%  F e r r i c - I r o n (Fe'' ')  0.01%  Manganese (Mn)  0.05%  Substances not p r e c i p i t a t e d by NH.0H 4 Z i n c (Zn)  0.050% 0.005%  - 21 -  C u p r i c s u l p h a t e , g r a n u l a r c r y s t a l s , B.D.H. reagent CuSO..5H„0 4 2  M.W.  249.69  Alkalies  (suphated)  n o t more than 0.5%  Chloride  (Cl)  n o t more than 0.005%  Iron  (Fe)  not more than 0.08%  Aluminum "AnalaR" Al  M.W.  B.D.H.  26.98  A c i d i n s o l u b l e matter Iron  (Fe)  0.005%  (Si)  0.01%  T o t a l n i t r o g e n (N)  3.3  test  0.004%  Copper (Cu) Silicon  passes  0.002%  P r e p a r a t i o n of S o l u t i o n s f o r H y d r o l y s i s The  aluminum s u l p h a t e s o l u t i o n was prepared by d i s s o l v i n g  aluminum s u l p h a t e Al^(SO^)^.I8H2O approximately  6.0 gr/£  i n d i s t i l l e d water.  A s o l u t i o n of  o f aluminum was made h a v i n g 3 0 2 ^ 1 ^ 0 2 r a t i o  of about  3.0, and a pH of 3.10.  was used  for hydrolysis.  The s o l u t i o n was f i l t e r e d b e f o r e i t  S o l u t i o n s of the lowest pH (pH = 0.70) used  i n t h i s work were prepared by d i s s o l v i n g A^C^SO^) sulphuric acid.  hydrated  ^. I8H2O  i n dilute  Any s o l u t i o n between these two l i m i t s (pH = 0.70 and  pH = 3.10) was prepared by m i x i n g s e l e c t e d r a t i o s of the two. S o l u t i o n s c o n t a i n i n g a l k a l i n e metal s u l p h a t e s and d i v a l e n t  metal  s u l p h a t e s a l t s were prepared by m i x i n g the s o l u t i o n o f the c o r r e s p o n d i n g s a l t w i t h aluminum s u l p h a t e s o l u t i o n . S o l u t i o n s of normal aluminum s u l p h a t e  were d i s c a r d e d a f t e r 7 days o f  - 22 storage.  Aluminum s u l p h a t e s o l u t i o n s c o n t a i n i n g excess  were kept  f o r a few weeks.  s u l p h a t e s were prepared  3.4  Chemical Initial  and  after hydrolysis.  ions.  f o r aluminum, s u l p h a t e ,  The pH of the s o l u t i o n s was measured b e f o r e  s u l p h a t e content was determined  Aluminum was determined  20  by p r e c i p i t a t i o n as BaSO^.  by complexing w i t h EDTA  *  and then back  the excess EDTA w i t h z i n c s u l p h a t e u s i n g d i t h i z o n e  an i n d i c a t o r and 1 M CH C00H-l M CH C00NH. s o l u t i o n o  o  3 Standard  metal  j u s t b e f o r e u s i n g them.  and f i n a l s o l u t i o n s were a n a l y z e d  added metal  titrating  Solutions containing alkaline  Analysis  and  The  sulphuric acid  3  as  as a b u f f e r .  4  aluminum s u l p h a t e s o l u t i o n was made from " A n a l a r " aluminum  by d i s s o l v i n g i t i n s u l p h u r i c a c i d . * disodium s a l t o f e t h y l e n e diamine  CH C00H  Na-OOCH„C  o  CH^COONa  H00CH C o  diphenylthiocarbazone  .H  II  H  S  H  II H  D i v a l e n t i r o n i n the aluminum s u l p h a t e s o l u t i o n was titrating  Fe  I|  w i t h CeCHSO^)^ to o x i d i z e i t to Fe  orthophenanthroline  ferrous sulphate  a n a l y z e d by  | | i  using  1,10-  ( F e r r o i n ) as an i n d i c a t o r .  t h i s case the aluminum content of the s o l u t i o n was determined d i f f e r e n c e i n EDTA used  from the  to t i t r a t e both i r o n and aluminum.  Copper and aluminum sulphate s o l u t i o n was a n a l y z e d by l i b e r a t e d 1^ w i t h ^2820^ to determine aluminum content was determined t i t r a t e both copper  the copper  titrating  content.  The  from t h e d i f f e r e n c e i n EDTA used t o  and aluminum.  The p r e c i p i t a t e d phase was a l s o a n a l y z e d f o r aluminum and sulphate.  The s o l i d  phase i s s o l u b l e i n s t r o n g s u l p h u r i c a c i d and  s t r o n g sodium h y d r o x i d e , s o l u t i o n s were used  and t h e r e f o r e the same methods as f o r the  for analysis.  Water content was  taken as the  d i f f e r e n c e between the t o t a l weight and the aluminum and s u l p h a t e content.  L i , Na and K content was determined  photometer.  c — C.>  ,c—c  \  c//  \  C=N  /  c — C//  \  \C ' N=C  [ F e ( C H N ) ] ++ 1 2  41 I  2  +  g  2  ++  2Cu  3  In  c a t i o n ; red colour  2CuI 21  +  I  2  by the "EEL" flame  - 24 -  4.  RESULTS AND DISCUSSION  The i n t e n t i o n of the work p r e s e n t e d i n t h i s t h e s i s was t o study the  change i n e q u i l i b r i u m h y d r o l y s i s o f aluminum s u l p h a t e  w i t h temperature, s u l p h u r i c a c i d c o n c e n t r a t i o n is  generally  by  the c o n c e n t r a t i o n  solutions  and o t h e r c a t i o n s .  It  known t h a t the amount of p r e c i p i t a t e d phase i s determined o f aluminum and s u l p h a t e i n the i n i t i a l  solution  3 for  a given  temperature.  aluminum i n the i n i t i a l possible  of  s o l u t i o n was not v a r i e d i n o r d e r to make i t  to e s t a b l i s h the e f f e c t o f other f a c t o r s .  are d i s c u s s e d 4.1  In the p r e s e n t work the c o n c e n t r a t i o n  under the f o l l o w i n g  Results  obtained  classifications:  The e f f e c t of temperature on h y d r o l y s i s o f aluminum s u l p h a t e solutions.  4.2  The e f f e c t o f s u l p h u r i c a c i d c o n c e n t r a t i o n  on h y d r o l y s i s o f  aluminum s u l p h a t e s o l u t i o n s . 4.3  The e q u i l i b r i u m  4.4  T e r n a r y diagrams f o r the A^O^-SO^-f^O  4.5  Mechanism o f the h y d r o l y s i s of aluminum  4.6  The e f f e c t aluminum  4.7  constants  of a l k a l i  sulphate.  m e t a l s u l p h a t e s on h y d r o l y s i s o f  sulphate.  The e f f e c t of d i v a l e n t m e t a l s u l p h a t e s on h y d r o l y s i s o f aluminum s u l p h a t e s o l u t i o n s .  4.8  system.  A p p l i c a t i o n of the h y d r o l y s i s  process.  - 25 4.1  The  -  E f f e c t o f Temperature on H y d r o l y s i s of Aluminum  Sulphate  Solutions At o r d i n a r y temperatures, sulphate w i l l in  c o n c e n t r a t e d s o l u t i o n s of aluminum  only c r y s t a l l i z e a b a s i c s a l t  the i n i t i a l  i f the S O ^ i A ^ O ^  ratio  3.0.  s o l u t i o n i s l e s s than 14  S. B r e t s z n a j d e r  has  o b t a i n e d normal aluminum s u l p h a t e from  clay  ( c a l c i n e d at 770-820°C f o r 1 h r ) b y l e a c h i n g i t w i t h d i l u t e s u l p h u r i c acid  f o r 10-12  h r s at 80°C and  c o o l i n g the f i l t r a t e  to  crystallize 3  the normal aluminum s u l p h a t e h y d r a t e . that at temperatures  I t was  r e p o r t e d by T.R.  h i g h e r than 1 1 0 ° C h y d r o l y s i s of aluminum s u l p h a t e  solutions with i n i t i a l  SO^A^O^ ratio  l e s s than 3.0  precipitates  c r y s t a l l i n e m a t e r i a l " b a s i c aluminum s u l p h a t e " (B.A.S.). is  related  The  3  = 40.6%; HyO  temperature  of  about 3.0  in  these experiments  in  i n the temperature  determined  range 125-250°C.  as l o n g as 16 h r s .  H y d r o l y s i s of Aluminum Sulphate H y d r o l y s i s experiments  at t h i s  u n f i l t e r e d s o l u t i o n s of pH = 3 . 1 0 . reproducible.  Retention  ratio time  equilibrium no  was  further  time.  S o l u t i o n s at 125°C  temperature  were done w i t h  R e s u l t s o b t a i n e d were not  When the same s o l u t i o n s were f i l t e r e d ,  h y d r o l y z e d , r e s u l t s were more u n i f o r m . at  The  by h y d r o l y z i n g  S02:Al202  from the h y d r o l y s i s curves when t h e r e was  the aluminum c o n c e n t r a t i o n w i t h p r o l o n g e d  4.1.1  ~  L  = 20.6%.  e f f e c t on h y d r o l y s i s was  was  as ^ 2°3  as f o l l o w s :  d i l u t e s o l u t i o n s of aluminum s u l p h a t e w i t h i n i t i a l  determined  T h i s compound  to the m i n e r a l a l u n i t e , h a v i n g a f o r m u l a expressed  3AI2O2.4SO2.9H2O w i t h a t h e o r e t i c a l c o m p o s i t i o n 38.8%; S 0  Scott  e q u a l time i n t e r v a l s were l e s s f o r  and  then  Hydrolysis yields  change  - 26 -  filtered  s o l u t i o n s , and, i n both c a s e s , n o t s u f f i c i e n t  analysis.  f o r chemical  F o r times which were l o n g enough t o e s t a b l i s h  h y d r o l y s i s y i e l d s were almost unfiltered  the same f o r both  equilibrium,  the f i l t e r e d  and the  s o l u t i o n s , thus s u g g e s t i n g t h a t a n u c l e a t i o n p r o c e s s p l a y s  an important  r o l e i n -the k i n e t i c s o f the r e a c t i o n a t t h i s  temperature.  R e s u l t s of the a n a l y s i s o f h y d r o l y z e d s o l u t i o n s a r e shown i n T a b l e 1 and F i g . 9.  '»  T a b l e 1.  Time a t 125°C hrs  H y d r o l y s i s o f aluminum s u l p h a t e s o l u t i o n s a t 125 C.  Al  i n s o l . SO. i n s o l . A l 4  prec.  SO^ p r e c .  pH  S0 /A1 0 3  gr/i>  1.00  6.09  -  0.01 .  -  2.98  -  3.00  5.89  -  0.21  -  2.53  -  5.00  5.80  31.70  0.30  0.70  2.24  1.31  6.00  5.69  31.33  0.41  1.07  1.80  1.47  7.00  5.68  31.34  0.42  1.06  1.80  1.41  12.50  5.76  31.30  0.34  1.10  1.78  1.82  13.75  5.65  31.38  0.45  1.02  1.79  1.27  16.50  5.68  31.38  0.42  1.02  1.78  1.36  solution :  3  i n the pre-  gr/Ji  Starting  2  gr/£  32.40 + 0.3 gr/£ S 0 . 6.10 + 0.05 gr/£ pH = 3.10  A  =  - 28 -  4.1.2  H y d r o l y s i s of Aluminum Sulphate S o l u t i o n s at 150°C Filtered  s o l u t i o n s of aluminum s u l p h a t e w i t h i n i t i a l  r a t i o of about 3.0  were h y d r o l y z e d a t 150°C f o r d i f f e r e n t  R e s u l t s o b t a i n e d are p r e s e n t e d  i n T a b l e 2 and F i g . 10.  e q u i l i b r i u m seems to be reached of the p r e c i p i t a t e d The  compound  i n 6.0  h r s and  the X-ray  2.  Time at 150°C  From F i g . 10  the SO^tA^O^ r a t i o  not s u f f i c i e n t  times.  f o r chemical  d i f f r a c t i o n pattern indicated that basic  aluminum s u l p h a t e e x i s t e d at t h i s temperature  Table  times.  remains unchanged w i t h p r o l o n g e d  amount of p r e c i p i t a t e d compound was  a n a l y s i s but  SO^rA^O^  (see Appendix  III-A).  H y d r o l y s i s of aluminum s u l p h a t e s o l u t i o n s at 150°C*  A l i n s o l . SO, i n s o l . A l p r e c . 4  hrs  gr/£  gr/£  SO. p r e c . 4  PH  s o :A1 0 3  2  i n the p r e c .  gr/£  1.00  5.28  30.44  0.82  1.96  1.67  1.34  2.00  5.07  29.96  1.03  2.44  1.55  1.33  3.00  4.84  -  1.26  -  1.45  -  4.00  4.76  -  1.34  -  1.45  -  6.00  4.64  28.65  1.46  3.75  1.40  1.44  10.00  4.64  28.60  1.46  3.80  1.38  1.46  16.00  4.65  28.64  1.45  3.46  1.44  1.34  Starting solution:  32.40 gr/2, 6.10 pH =  gr/£ 3.10  SO Al  3  - 30 4.1.3  Hydrolysis of Aluminum Sulphate Solutions at 175°C  F i l t e r e d solutions of aluminum sulphate with i n i t i a l  SO^iA^O^  r a t i o of about 3.0 were hydrolyzed at 175°C and results obtained are presented i n Table 3 and F i g . 11.  The precipitated phase has a r a t i o  of SOyA^O^ of about 1.32 (calculated from F i g . 11) corresponding to the r a t i o of basic aluminum sulphate. confirmed the presence  Analysis of the s o l i d phase  of the basic aluminum sulphate (see Appendix  II, f o r Chem. Anal, and Appendix III-B f o r X-ray d i f f . patterns.).  Table 3.  Hydrolysis of aluminum sulphate solutions at 175 C  Time at A l i n s o l . SO 175°C  i n s o l . A l prec.  4  hrs.  *  gr/Jl  gr/>!  gr/£  SO *  prec.  pH  SO :A1 0» 9  i n the prec.  gr/£  1.00  4.45  28.53  1.54  3.87  1.30  1.32  2.00  3.96  27.26  2.14  5.14  1.27  1.35  4.00  3.68  26.76  2.42  5.64  1.18  1.31  6.00  3.56  26.39  2.54  6.01  1.15  1:33  10.00  3.55  26.40  2.55  6.00  1.15  1.32  16.30  3.50  26.40  2.60  6.00  1.15  1.30  Starting solution:  32.40 gr/£ S0 6.10 gr/£ A l pH = 3.10  4  '  J  0  "  •  2  -J  1  3  4  1  5  I  >  6  7  I  8  !  9  *  '  '  '  '  I  10  II  12  13  14  15  Fig II. HYDROLYSIS OFALUMINIUM SULPHATE AT 175 C°  timeinhrs.  L_  16  - 32  4.1.4  Hydrolysis Solutions  of Aluminum Sulphate S o l u t i o n s  with i n t i a l  SO^ikl^O^  at 200°C f o r as long as 18 h r s . 4 and  F i g . 12.  SO^iAl^O^ r a t i o  The  -  ratio  Results  Appendix I I I - C  4.  Time at 200°C  were h y d r o l y z e d  o b t a i n e d are shown i n T a b l e  of the p r e c i p i t a t e d compound c a l c u l a t e d from F i g . Analysis  f o r X-ray d i f f .  Hydrolysis  Al i n s o l .  (see Appendix I I f o r Chem. a n a l ,  pattern).  of aluminum s u l p h a t e  SO, i n s o l . 4  Al  prec.  s o l u t i o n s at  200°C  SO, p r e c 4  pH  *  S0 :A1 0 3  2  hrs.  gr/2,  1.00  3.30  25.78  2.80  6.62  1.07  1.33  2.00  3.01  24.98  3.09  7.42  1.03  1.35  4.00  2.71  24.32  3.39  8.08  0.99  1.34  6.00  2.51  23.91  3.59  8.49  0.98  1.33  6.45  2.51  23.89  3.59  8.51  0.98  1.33  18.00  2.40  23.65  3.70  8.75  0.98  1.33  Starting solution:  gr/£  gr/£  32.40 gr/SL 6.10 pH =  12  of s o l i d phase shows t h a t the p r e c i p i t a t e d  compound i s the b a s i c aluminum s u l p h a t e  Table  of about 3.0  e q u i l i b r i u m h y d r o l y s i s y i e l d i s h i g h e r than at 175°C.  i s about 1.31.  and  at 200°C  gr/£ 3.10  S0~ Al  i n the  gr/£  3  prec.  The  0  I  2  3  4  5  6  7  8  9  10  II  12  Fig.12. HYDROLYSIS OF ALUMINIUM SULPHATE AT 2 0 0 C °  13  14  15  timsinhrs.  16  - 34 -  4.1.5  H y d r o l y s i s of Aluminum Sulphate Filtered  ratio  s o l u t i o n s of aluminum  of about 3.0 were h y d r o l y z e d  shown i n Table 5 and F i g . 13.  sulphate with i n i t i a l  H y d r o l y s i s y i e l d s are very high. 1.33  sulphate  The  ( c a l c u l a t e d from F i g .  A n a l y s i s of the s o l i d phase showed the c o m p o s i t i o n  aluminum  SO^iA^O^  at 225°C and r e s u l t s o b t a i n e d a r e  p r e c i p i t a t e d phase has an S O ^ A l , ^ r a t i o 13).  S o l u t i o n s a t 225°C  of b a s i c  (see Appendix I I f o r Chem. a n a l , and Appendix I I I - D  f o r X-ray d i f f . p a t t e r n ) .  Table  5.  Time at 225°C  H y d r o l y s i s of  aluminum s u l p h a t e s o l u t i o n s at 225°C  A l i n s o l . SO. i n s o l . A l 4  hrs.  gr/l  gr/H  prec. gr/n  SO, p r e c . 4  pH  SO  3  : A 1  2°3  i n the p r e c .  gr/X,  1.00  1.89  22.45  4.21  9.95  0.89  1.33  1.00  1.88  22.35  4.22  10.05  0.92  1.34  2.00  1.80  22.31  4.30  10.09  0.92  1.32  2.00  1.73  21.55  4.37  10.85  0.89  1.39  3.00  1.65  21.96  4.45  10.44  0.88  1.32  5.00  1.58  21.40  4.52  11.00  0.89  1.37  8.40  1.44  21.36  4.66  11.04  0.85  1.33  16.00  1.48  21.63  4.54  10.77  0.85  1.33  * Starting  solution:  32.40 gr/j> 6.10 pH =  S0  gr/Z A l 3.10  4  Fig. 13- HYDROLYSIS OF ALUMINIUM SULPHATE AT 2 2 5 C*  timemhrs  - 36 -  4.1.6  H y d r o l y s i s o f Aluminum Sulphate Filtered  and  S o l u t i o n s a t 250°C  s o l u t i o n s o f aluminum s u l p h a t e were h y d r o l y z e d a t 250°C  i t was found  t h a t t h e amount of p r e c i p i t a t e d b a s i c aluminum  s u l p h a t e on h e a t i n g the a u t o c l a v e t o t h i s temperature was comparable to the amount o f b a s i c s a l t p r e c i p i t a t e d i n 16 h r s a t 225°C. suggests  t h a t t h e r e a c t i o n r a t e above 225°C must be v e r y h i g h .  o b t a i n e d at t h i s The  This  temperature a r e shown i n T a b l e 6 and F i g . 14.  S O ^ A ^ O ^ r a t i o of the p r e c i p i t a t e d compound i s 1.33.  of t h e s o l i d  Results  corresponds  t o t h e b a s i c aluminum s u l p h a t e  Analysis  (see Appendix  I I f o r Chem. a n a l , and Appendix I I I - E f o r X-ray d i f f . p a t t e r n ) .  T a b l e 6.  Time at 250°C  H y d r o l y s i s of aluminum s u l p h a t e at  A l i n s o l . SO, i n s o l . A l 4  prec.  250°C*  SO^  prec.  P  H  S0 :A1 0 3  in  2  the p r e c .  hrs.  gr/£  gr/£  gr/£  gr/£  0.00  1.52  21.57  4.58  10.83  0.85  1.33  1.00  0.97  20.27  5.13  12.13  0.80  1.33  3.30  0.88  20.27  5.22  12.13  0.80  1.31  6.30  0.91  20.13  5.19  12.27  0.79  1.33  * Starting solution:  32.40 gr/2, SO 6.10  gr/£ A l  pH = 3.10  3  o ca  o  0  PH  < vI 6.0 J  o  \  l  O  Al  Q  S0|  3.0  1-30  -28 2.0 4 - 26  V PH  5.0 1  o  4.0  24 1.0  -I  Co  22 3.0 H h20 2.0 H  \ \  18 16  I.OJ  1  3  '  1  1  2  1  3  •  4  1  5  1  6  L  7  1  8  1  9  I  I  I  •  10  II  12  13  Fig. 14. HYDROLYSIS OF ALUMINIUM S U L P H A T E AT 2 5 0 C °  •  14  15  16  timeinhrs.  - 38 -  4.2  The  E f f e c t of S u l p h u r i c A c i d C o n c e n t r a t i o n on H y d r o l y s i s  of  Aluminum Sulphate  Solutions  Most of the work on h y d r o l y s i s of aluminum s u l p h a t e was s o l u t i o n s having for  t h i s was  tures.  initial  S O ^ A l ^ O ^ r a t i o l e s s than  3.0.  The  to o b t a i n h i g h y i e l d s i n a s h o r t time and  If hydrolysis i s  at low  done on reason tempera-  to be used as a p u r i f i c a t i o n p r o c e s s f o r  l e a c h s o l u t i o n s h i g h e r c o n c e n t r a t i o n s of s u l p h u r i c a c i d would be expected.  In the work p r e s e n t e d  i n t h i s t h e s i s a s e r i e s of experiments  w i t h s o l u t i o n s c o n t a i n i n g about 6.0  gr/£  c o n c e n t r a t i o n s of s u l p h u r i c a c i d was  aluminum and  done.  different  H y d r o l y s i s curves i n the  p r e v i o u s p a r t were used to determine the r e t e n t i o n time temperatures of  225°C and  250°C.  These two  the h i g h y i e l d s at s h o r t times  r a t i o of about  4.2.1  3  2  3  Ratio >  3.0  250°C f o r 4 h r s .  sulphate  i  !  The h i g h e s t S 0 : A 1 0 3  about 4.63.  increased  decreased.  Solutions with  Initial  s u l p h u r i c a c i d were h y d r o l y z e d 2  3  r a t i o used i n t h i s  at  s e t of  R e s u l t s o b t a i n e d are shown i n T a b l e 7 and  As the c o n c e n t r a t i o n of excess  s o l u t i o n was  SO^rA^O^  a t 250°C  F i l t e r e d s o l u t i o n s w i t h excess  15.  were chosen because  w i t h s o l u t i o n s h a v i n g an  H y d r o l y s i s of Aluminum Sulphate  experiments was  two  3.0.  S0 :A1 0  Fig.  temperatures  f o r the  a c i d i n the  initial  the amount of p r e c i p i t a t e d b a s i c aluminum  - 39 -  ~~i  22  r~  24  —T" 28  26  n 30  1 32  1 34  1 36  1 r 38 SO^jn sol. gr/1.  O Al  0  S  °4  VPH  '0  o  o 0  IO  v  3.0  2.0  — L —  —r-  4.0 AI in sol. gr/1. + 2.0 finalpH  0 ACID ALUMINIUM Fig.15. HYDROLYSIS 1.OF SULPHATE A T 2 5 0 C *  - 40  Table.7.  The  e f f e c t of  excess s u l p h u r i c  a c i d on h y d r o l y s i s o f  aluminum s u l p h a t e a t 250°C.  pH initial  SOT i n i t . 4 gr/£  Al  insol. gr/Jl  SO, i n s o l . 4 gr/£  Al  p r e c . SO^ p r e c .  pH  gr/£  gr/A  final  0.70  50.08  3.31  43.43  2.79  6.65  0.56  1.00  44.26  2.17  34.97  3.93  9.29  0.60  1.50  37.05  1.25  25.45  4.85  11.60  0.70  2.00  34.08  1.00  22.05  5.10  12.03  0.76  2.50  33.21  0.98  21.13  5.12  12.08  0.78  3.10  32.40  0.91  20.13  5.19  12.27  0.80  4.2.2  H y d r o l y s i s o f Aluminum Sulphate S0 :A1 0 3  3  Solutions with  Initial  R a t i o > 3.0 a t 225°C  F i l t e r e d s o l u t i o n s o f aluminum s u l p h a t e were h y d r o l y z e d a t 225°C for  6 hrs.  Initial  s o l u t i o n s used i n this set  same as s o l u t i o n s used a t 250°C. with i^preasing  0  f experiments were the  Hydrolysis yields  pH o f the i n i t i a l  solution.  from t h i s s e t o f experiments a r e p r e s e n t e d  increased  Results  obtained  i n T a b l e 8 and F i g . 16.  - 41 ~i—  22  26  30  I  i 34  p  — r — 38  42  i  i  S O 4 in soLgr/l.  X o. 3.0 H  1.0  20  3.0 •  -4  ,-.  .~  IX)  4.0  A l i n sol.gr/1.  Fig. 16. HYDROLYSIS OF ACID ALUMINIUM SULPHATE AT 2 25C°  f-  2 0 pH final  - 42 -  T a b l e 8.  The  e f f e c t of  excess s u l p h u r i c  a c i d on h y d r o l y s i s of  aluminum s u l p h a t e a t 225°C.  pH  SO. i n i t . 4 gr/£  initial  Al  pH i n s o l . SO. i n s o l . A l p r e c . SO^ p r e c . 4 final gr/£ gr/£ gr/a gr/A  0.70  50.08  4.94  47.04  1.16  3.04  0.65  1.00  44.26  3.62  38.35  2.48  5.91  0.70  1.50  37.05  2.33  28.37  3.77  8.68  0.78  2.00  34.08  1.87  24.10  4.23  9.98  0.83  2.50  33.21  1.63  22.60  4.47  10.61  0.84  3.10  32.40  1.50  21.52  4.60  10.88  0.85  4.3  The E q u i l i b r i u m Application  that  Constants  of the phase r u l e to the system Al^O^-SO^-H^O  a t constant temperature,  i n v a r i a n t when i n e q u i l i b r i u m  a s o l u t i o n composition w i t h two s o l i d  3A1 0 .4S0 .9H 0 (B.A.S. - the most b a s i c 2  3  3  If  phases, e.g. A ^ O ^ n R ^ O and  salt).  the b a s i c  point,  phase to p r e c i p i t a t e i s always the o x i d e , but the s o l u t i o n  composition w i l l  point  e x i s t s which i s  the s t a r t i n g s o l u t i o n has a c o m p o s i t i o n below t h i s  the f i r s t  requires  salt  change i n t h e d i r e c t i o n of the i n v a r i a n t p o i n t  also p r e c i p i t a t e s .  P ( F i g . 17) w i l l  The l o c a t i o n o f the i n v a r i a n t  change w i t h the temperature.  until  Fig.I 7 . PHASE DIAGRAM OF THE  A I 2 O 3 - S O 3 - H 2 O  SYSTEM  - 44 If the solution composition i s below the invariant point P at the temperature T and above the invariant point at any temperature  higher  than T, then the oxide w i l l p r e c i p i t a t e i n the early stages of heating and at l a t e r stages the basic s a l t w i l l p r e c i p i t a t e while the oxide w i l l tend to redissolve.  Eventually the oxide may completely disappear  i f the composition of the solution i s such that i t i s above the invatiant point.  In the work of T.R. Scott, a second phase (A^O^m^CO  was not observed because the hudrolysis was carried out at high concentrations of aluminum i n solutions and i t can only be expected to p r e c i p i t a t e from d i l u t e solutions of basic aluminum sulphate. The X-ray d i f f r a c t i o n patterns did not show the presence of A^O^ i n the s o l i d phase and therefore i t can be concluded that the solution composition i s above the invariant point where only one phase exists i n equilibrium with the l i q u i d phase.  The X-ray d i f f r a c t i o n pattern  of the p r e c i p i t a t e obtained at 125°C, was very poor so that no conclusion about the presence of aluminum oxide could be made. I f there i s only one s o l i d phase i n equilibrium with l i q u i d phase at a l l temperatures should occur.  from 125°C up to 250°C, then the same hydrolysis reaction For such a reaction, the slope of a plot of log  [equilibrium constant] vs. 1/T°K should be l i n e a r . 21 R.G. Robins  has reported values f o r the second d i s s o c i a t i o n  constant of sulphuric acid up to about 200°C which are i n good agreement with the values calculated from the correspondence these constants, are given i n Table 9.  principle.  Values of  The presence of aluminum sulphate  w i l l s h i f t the equilibrium to the l e f t i n the reaction 4SC> " J H 4  Therefore only HSO^  ions w i l l exist i n solution.  +  + SO^".  Assuming that aluminum  sulphate i s completely dissociated, and that only HSO,  i o n can exist  - 45 -  T a b l e 9.  E q u i l i b r i u m c o n s t a n t s f o r the r e a c t i o n HSO, 4  T°C  log K  -»•  H  125  150  175  200  225  250  -3.53  -3.89  -4.40  -4.72  -5.95  -6.05  i n s o l u t i o n i n the temperature  range  .125-250°C  +  + SO. 4  the h y d r o l y s i s  reaction  can be w r i t t e n a s :  6A1  444  " + 4HS0. 4  + 14KL0 2  — — —  3Al 0„.4S0 .9H 0 2 3 3 2 o  o  o  + 14H  (1)  +  The e q u i l i b r i u m c o n s t a n t f o r t h i s r e a c t i o n can be e x p r e s s e d a s :  K  =  )  ( 2  [A1 ] [HS0 "]^ W  D  4  An e x p r e s s i o n f o r the v a r i a t i o n of the e q u i l i b r i u m c o n s t a n t K w i t h temperature i s d e r i v e d  -AG  0  by combining  = RT in K  (3)  and 9T ^ T  ; J  P  T  2  '  K  Therefore ,9 in K. 9T P ;  =  d&n K dT  =  AH°_  2  ,,-\ U  J  Kl  assuming  thatAH°  is virtually  (5) can be a l s o w r i t t e n as  independent of temperature.  Equation  - 46  din K dl/T  -  AH° R  =  . . { b )  Thus, i f £n K i s p l o t t e d a g a i n s t point  i s equal to -AH°/R.  constant  (2) i t f o l l o w s  - l o g K = 14pH  1/T  the s l o p e  From the e x p r e s s i o n  curve at  f o r the  any  equilibrium  that  + 6 log  [Al  + + +  ] + 4 log  The  pH  of the h y d r o l y z e d s o l u t i o n s was  and  as such i t i s d i f f e r e n t from the pH  The  change i n the  t h a t the pH  of the  [HS0 ~]  (7)  4  measured at room temperature at which the r e a c t i o n  d i s s o c i a t i o n c o n s t a n t of water  (Table  10)  of the s o l u t i o n should decrease w i t h i n c r e a s i n g  occurs.  i s such temperature.  T a b l e 10.  Hydrolysis  T  25  60  100  150  200  250  300  350  14.0  13.05  12.21  11.65  11.30  11.18  11.19  11.33  C°  -log  K  True but  pH  value  i t cannot be  c o n s t a n t of water  at any  temperature can be  e a s i l y measured.  The  pH  or c o o l i n g an e l e c t r o l y t e s o l u t i o n i s due  defined  change which o c c u r s i n to the h y d r o l y s i s  change i n a c t i v i t y of a l l i o n s i n s o l u t i o n .  Assuming t h a t  h y d r o l y z e d s o l u t i o n s remains unchanged w i t h temperature the constant  f o r the h y d r o l y s i s r e a c t i o n can be  temperature.  thermodynamically heating  and the pH  of  equilibrium  c a l c u l a t e d at each  - 47  -  R e s u l t s of the e q u i l i b r i u m h y d r o l y s i s of normal aluminum s u l p h a t e s o l u t i o n s i n the temperature 11 and  F i g . 18.  range  125-250°C are p r e s e n t e d  i n Table  R e s u l t s i n T a b l e 7 and T a b l e 8 were a l s o used  to  c a l c u l a t e the e q u i l i b r i u m c o n s t a n t s f o r h y d r o l y s i s of aluminum s u l p h a t e s o l u t i o n s w i t h excess log K  Table  are p r e s e n t e d  11.  Temp.  i n Table  Calculated  v a l u e s of  12.  Equilibrium  h y d r o l y s i s of normal aluminum s u l p h a t e i n  temperature  range  the  125-250°C.  Aluminum i n s o l .  Sulphate i n s o l .  pH  °C  gr/a  gr/Ji  125  5.68  31.35  1.78  150  4.65  28.65  1.42  175  3.50  26.40  1.15  200  2.45  23.80  0.98  225  1.46  21.60  0.85  250  0.90  20.20  0.79  Table  12.  Values of l o g K f o r the h y d r o l y s i s of aluminum s u l p h a t e solutions with  Init. log l  sulphuric acid.  o  g  K K  pH  2 2 5  250  excess s u l p h u r i c a c i d at 225°C  and 250°C  0.70  1.00  1.50  2.00  2.50  3.10  -3.43  -2.96  -2.42  -2.16  -1.93  -1.77  -1.00  0.00  0.513  0.503  0.374  0.35  - 48 -  - 49 -  Mean e q u i l i b r i u m c o n s t a n t s f o r 225°C and 250°C were c a l c u l a t e d T a b l e 12 and were found  log K log K  T a b l e 13  2 2 5 < > c  2  5  0  o  c  to be:  = -2.44  K = 3.62 x 10  =  K = 2.0  0.302  p r e s e n t s the e q u i l i b r i u m c o n s t a n t s f o r h y d r o l y s i s  of aluminum s u l p h a t e i n the temperature  T a b l e 13.  from  reaction  range 125-250°C.  E q u i l i b r i u m c o n s t a n t s f o r the h y d r o l y s i s  r e a c t i o n of  aluminum s u l p h a t e  1/T x 1 0  4  log K  25.10  -18.92  1.2 x 1 0 "  23.60  -13.20  6.3 x I O  22.30  - 8.63  2.3 x 1 0 "  21.10  - 5.05  8.9 x I O  20.05  - 2.44  3.6 x 1 0 ~  19.10  +• 0.302  2.0 .  S i n c e the p l o t of l o g K a g a i n s t it  T°C  1/T°K  1 9  125  - 1 4  150  9  175  - 6  200 225  3  1/T g i v e s a s t r a i g h t  250  line  ( F i g . 19)  i s most p r o b a b l e t h a t t h e r e i s o n l y one s o l i d phase i n e q u i l i b r i u m  w i t h t h e l i q u i d phase.  T h e r e f o r e t h e s o l u t i o n composition  the i n v a r i a n t p o i n t P ( F i g . 17) at a l l temperatures.  i s above  ,9  ~^~0  3  Zi  ?i  Fig. 19.THE CHANGE OF EQUILIBRIUM CONSTANT WITH TEMPERATURE  24  . ^ 5  - 51 -  4.4  T e r n a r y Diagrams f o r the System  Al^O^-SOy-H^O  Some d a t a i s a v a i l a b l e on the h y d r o l y s i s  o f b a s i c aluminum s u l p h a t e  3 at temperatures  up to 220°C,  but no u s e f u l d a t a i s a v a i l a b l e on  h y d r o l y s i s of a c i d aluminum s u l p h a t e s o l u t i o n s . from S e c t i o n  4.2 was used  Experimental  data  t o c a l c u l a t e the e q u i l i b r i u m l i q u i d  t i o n i n a c i d aluminum s u l p h a t e s o l u t i o n s a t 225 and 250°C.  composi-  Ternary  diagrams were c o n s t r u c t e d f o r the water c o r n e r of the A 1 0 " S 0 - H 0 2  system at 225 and 250°C. the i n i t i a l  T a b l e 14.  3  3  T a b l e s 14 and 15 show the c o m p o s i t i o n o f  and f i n a l s o l u t i o n s a t 250 and 225°C.  S o l u t i o n c o m p o s i t i o n a t 250°C comp. wt %  Starting l i q . A1 0 2  3  so  3  2  Equil. l i q .  H 0  A1 0  2  2  3  comp. wt %  so  3  H 0 . 2  1  1.12  4.10  94.78  0.51  3.52  95.98  2  1.12  3.59  95.29  0.40  2.84  96.76  3  1.12  3.00  95.88  0.23  2.07  97.70  4  1.12  2.77  96.11  0.184  1.79  98.03  5  1.12  2.69  96.20  0.18  1.72  98.10  6  1.12  2.64  96.24  0.168  1.63  98.20  - 52 T a b l e 15.  S o l u t i o n c o m p o s i t i o n a t 225°C  Starting l i q . A1 0 2  so  3  comp. wt % 3  Equil.  H 0  A1 0  2  2  liq.  comp. wt %  so  3  HgO  3  1  1.12  4.10  94.78  0.91  3.81  95.28  2  1.12  3.59  95.29  0.66  3.11  96.23  3  1.12  3.00  95.88  0.43  2.31  97.26  4  1.12  2.77  96.11  0.345  1.96  97.69  5  1.12  2.69  96.20  0.30  1.84  97.86  6  1.12  2.64  96.24  0.276  1.75  97.97  The  d a t a from T a b l e s 14 and 15 a r e p r e s e n t e d g r a p h i c a l l y i n F i g . 20  and  21.  The i n t e r s e c t i o n o f the i n i t i a l  l i n e s suggests  and f i n a l l i q u i d  the p o s s i b i l i t y o f the presence  the system a t 250 and 225°C.  composition  o f a second phase i n  The second phase i s p r o b a b l y a normal  aluminum s u l p h a t e but i t c o u l d n o t be d e t e c t e d i n any o f the experiments from the X-ray d i f f r a c t i o n p a t t e r n s o f the s o l i d . experiments A^ and A  2  w i t h s o l u t i o n s o f the composition  a number o f  c o r r e s p o n d i n g t o the p o i n t s  i n F i g . 20 and 21 were done, the presence  c o u l d not be unambiguously  Although  of a second  phase  proven.  A c i d aluminum s u l p h a t e s o l u t i o n s  (compositions A^ and A  20 and 21) were h y d r o l y s e d f o r predetermined  2  - Figs.  times, and s o l u t i o n  samples  were taken.  The a u t o c l a v e and the remaining m a t e r i a l was c o o l e d t o room  temperature,  and the r e s u l t i n g s o l u t i o n was a n a l y z e d .  i n s o l u t i o n compositions,  the S 0 : A 1 0  p r e c i p i t a t e was c a l c u l a t e d .  3  I t was  2  3  From the d i f f e r e n c e  r a t i o o f the r e - d i s s o l v e d  - 53 -  - 54 -  - 55 -  found to be s l i g h t l y increased but i t was f a r from the SO^.-AJ^O^ r a t i o of a normal s a l t .  4.5  Mechanism of the Hydrolysis of Aluminum Sulphate In aqueous solutions aluminum sulphate i s at least p a r t i a l l y  dissociated into i t s constituents.  Al (S0 ) (aq) 2  The A l  4  ^  3  2A1  +  3S0  (8)  4  i o n i n solution w i l l react with ^ 0 to give:  Al" " " " 1  1  1  +  H0  *  2  The concentration of A1(0H) tion of A l  -H-  and H  AKOH)" ^ 1  H  (9)  +  i n solution w i l l depend on the concentra-  i n the i n t i a l solution.  solution reacts with HS0  A1(0H)  cation i n  ion to give the basic aluminum sulphate:  4  eAKOH)""" + 4HS0 " + 8H 0 —»1  +  1  4  2  3A1 0 .4S0 .9H 0 + 8H 2  3  3  +  2  (10)  22 The equilibrium.constant for reaction (9) was reported by Helgeson -4. 75 and i t i s 10  *  f o r d i l u t e solutions.  Because of the change i n the  d i s s o c i a t i o n constant of water with temperature this constant w i l l change, and become more and more p o s i t i v e as the temperature i s increased. reaction:  Helgeson gives the equilibrium constant values f o r the A1(0H)  >-  Al  +  OH  i (11)  - 56 -  Reaction  (9) i s simply a combination  H 0 2  - — v H  +  +  of r e a c t i o n (11) and  0H~  (12)  Knowing the e q u i l i b r i u m c o n s t a n t s a t temperatures for  up t o 300°C  r e a c t i o n s (11) and (12) the e q u i l i b r i u m c o n s t a n t  f o r r e a c t i o n (9)  can be c a l c u l a t e d from the r e l a t i o n :  log K  9  =  log K  Calculated values f o r  1 2  - log  K  n  a r e g i v e n i n T a b l e 16.  I | |  T a b l e 16.  E q u i l i b r i u m constants f o r r e a c t i o n A l A1(0H)  Temp °C log K  +  + +  H  +  R^O  «-  +  25  50  60  100  -4.75  -3.87  -3.53  -2.26  150  200  -0.84  +0.63  . 250 +1.97  300 +3.31  Precipitation  r e a c t i o n (10) i s a f a s t r e a c t i o n as can be seen from the  precipitation  curves a t h i g h temperatures  where i t reaches e q u i l i b r i u m  d u r i n g the h e a t i n g p e r i o d .  4.6  The E f f e c t o f A l k a l i Aluminum Sulphate  M e t a l Sulphates  on H y d r o l y s i s o f  a t 225°C  When s u l p h a t e s o f L i , Na o r K a r e p r e s e n t s o l u t i o n s during h y d r o l y s i s , corresponding  i n aluminum s u l p h a t e  a l u n i t e s of the g e n e r a l form  - 57 M2O.3Al2O2.4sO3.6H2O sulphate.  are p r e c i p i t a t e d instead of basic aluminum  Since the s o l u b i l i t y of these compounds i s less than the  s o l u b i l i t y of basic aluminum sulphate ("Hydrogen Alunite") the hydrolysis y i e l d s are higher and very close to 100%.  3 P.T. Davey and T.R.  Scott  have reported complete p r e c i p i t a t i o n  of aluminum i n 30 min.at 220°C from solutions with i n i t i a l SO^iA^O^ r a t i o of. 2.87.  The r a t i o of I^SO^:Al (SO^)3  calculated on the basis  2  of aluminum present i n s t a r t i n g solution was compound was  2.16.  The precipitated  of a composition corresponding to K 2 O . 3 A l 2 O 3 . 4 S O 3 . 6 H 2 O . 13  V.S. Sazhin, A.K.  Zapolskii and N.N.  Zakharova  have studied  hydrolysis of aluminum sulphate solutions having an i n i t i a l molar r a t i o of I^SO^iA^CSO^^ of 0.33. i n solution was  308 gr/&  Concentration of aluminum sulphate  (0.9 M), having S 0 : A 1 0 3  2  3  r a t i o of  Such solutions were hydrolyzed for 1 hr i n the temperature 175-250°C.  Maximum hydrolysis y i e l d at 250°C was  results show the presence  of two s o l i d phases.  3.0. range  about 82%. In the  Their  temperature  range 175-190°C, basic potassium-aluminum sulphates of the form K^SO^.3AI2O3.4SO3.9H2O  are precipitated.  At temperatures  than 230°C, alunites are formed with the formula K^O In the temperature two.  higher  .3AI2O3.4SO3.6H2O.  range 190-230°C they have reported a mixture of the  In order to see the effect of a l k a l i  metal sulphates on  hydrolysis of d i l u t e solutions of aluminum sulphate, solutions with M2S0 :Al2(30^)3 4  S0 :A1 03 3  2  2  4  gr/£ aluminum with  r a t i o of about 3.0 were hydrolyzed at 225°C u n t i l  equilibrium was K S0 .  r a t i o of about 0.5 containing 6.10  established. ^SO^  corresponds to I^SO^, N a 2 S 0 ^ and  - 58 4.6.1  The E f f e c t of Lithium Sulphate on Hydrolysis of Aluminum Sulphate at 225°C Aluminum sulphate-lithium sulphate solution containing 6.12 gr/£  aluminum, 38.30 gr/£ SO^  and 0.815 gr/£ lithium was hydrolyzed at  225°C u n t i l equilibrium was reached.  The results obtained are  presented i n Table 17 and F i g . 22.  Table 17.  Hydrolysis of aluminum sulphate-lithium sulphate solution at 225°C* I ||  Time at A l 225°C  —  =  i n s o l SO, i n s o l L i i n s o l A l prec SO, prec  L i prec  pH  hrs  gr/£  gr/£  gr/£  gr/£  gr/£  0  1.74  27.87  0.44  4.38  10.43  0.375  0.82  1  1.29  26.71  0.40  4.83  11.59  0.415  0.78  2  1.16  26.48  0.39  4.96  11.82  0.425  0.75  3  1.07  26.36  0.39  5.05  11.94  0.425  0.71  3  1.11  26.36  0.39  5.01  11.94  0.425  0.73  5  1.05  26.37  0.39  5.07  11.93  0.425  0.72  8  1.05  26.36  0.39  5.07  11.94  0.425  0.72  Starting solution:  38.30 gr/£ SO 6.12 gr/£ A l 0.815 gr/£ L i pH = 3.05  ,gr/£  o c  O Al  x  —  c:  o^ to  a. • _ " ]o  < 6.0 -I ?\  D L i  0  S.O'-  40  o c  o (0 » .  -1.0  34  S O 4  V PH  _| ;i\  V  v  36  _  V  —  0  32  8  _  3  ^|  0  VO  -0.6  2  8  3.026  20-j  V  •  n  n  n  - 0 . 4 24 -  n  O  O  -  22 -  -0.2  20 •  1.0 -  0  1 2  Fig. 2  2.  3  4  5  6  7  8  9  10  II  12  HYDROLYSIS OF LITHIUM-ALUMINIUM SULPHATE  SOLUTION AT 2 2 5 C °  13  time in hrs.  - 60  The p r e c i p i t a t e d was  found  compound was  -  analyzed  (see App.  t o be L i 2 O . 3 A l 2 O 2 . 4 S O 2 . 6 H 2 O .  I I ) and  i t s composition  In a f o u r component system  such as t h i s , i t i s normal to have at l e a s t  two  s o l i d phases i n  e q u i l i b r i u m w i t h the l i q u i d phase, but s i n c e the c o n c e n t r a t i o n o f L i  +  i o n s i n s o l u t i o n i s h i g h enough to p r e c i p i t a t e a l l the aluminum p r e s e n t i n the s t a r t i n g s o l u t i o n as l i t h i u m a l u n i t e , o n l y one precipitated.  The X-ray  d i f f r a c t i o n p a t t e r n f o r both b a s i c aluminum  s u l p h a t e and b a s i c lithium-aluminum it  is difficult  s o l i d phase i s  s u l p h a t e i s almost  to d i s t i n g u i s h between the two  the same, so  (see App.  III-K  and  III-E).  4.6.2  The E f f e c t of Sodium Sulphate on H y d r o l y s i s of Aluminum Sulphate at 225°C. Aluminum sulphate-sodium  A l " " , 2.625 gr/£ N a 4-1  4  About 5.0  gr/£  to 225°C.  +  38.14  of aluminum was  gr/£  S0  = 4  was  h y d r o l y z e d at 225°C.  s o l u t i o n was  reached  about 98%  precipitated  r e s u l t s o b t a i n e d i n t h i s s e t of experiments  T a b l e 18 and composition X-ray  F i g . 23.  A n a l y s i s of p r e c i p i t a t e d  corresponding  gr/£  p r e c i p i t a t e d w h i l e h e a t i n g the system  When the e q u i l i b r i u m was  p r e s e n t i n the i n i t i a l The  and  s u l p h a t e s o l u t i o n c o n t a i n i n g 6.12  of the aluminum  as a b a s i c s a l t . are p r e s e n t e d i n s o l i d phase shows the  to N a 2 O . 3 A l 2 O 2 . 4 S O 2 . 6 H 2 O  (see App.  II).  d i f f r a c t i o n p a t t e r n of t h i s compound i s the same as f o r b a s i c  aluminum s u l p h a t e and  lithium alunite  (see App.  III-H).  The  - 61 Table 18. H y d r o l y s i s of aluminum sulphate-sodium sulphate s o l u t i o n at 225°C* Time at A l 225°C  i n s o l SO. i n s o l N a 4  +  i n s o l A l prec SO^ prec  Na prec  pH  hrs  gr/a  gr/il  gr/il  gr/il  gr/il  gr/il  0  1.05  26.06  1.44  5.07  12.08  1.185  0.77  1  0.41  24.58  1.00  5.71  13.56  1.625  0.70  2  0.24  24.19  0.925  5.88  13.95  1.70  0.69  2  0.32  24.06  0.925  5.80  14.08  1.70  0.69  4  0.17  24.04  0.925  5.95  14.10  1.70  0.63  8  0.13  23.84  0.925  5.99  14.20  ' 1.70  0.63  *  Starting solution:  38.14 6.12  gr/Jl  = SO^  gr/Jl A l  2.625  gr/il  Na  pH = 3.09  4.6.3.  The E f f e c t of Potassium Sulphate on H y d r o l y s i s of Aluminum Sulphate at 225°C  Potassium sulphate-aluminum sulphate s o l u t i o n containing 6.12 aluminum, 4.465 gr/£ potassium and 38.14 gr/£ SO^ 225°C.  was hydrolyzed at  About 97% p r e c i p i t a t i o n occurs i n heating the system to 225°C.  100% p r e c i p i t a t i o n occurs i n only a few minutes at 225°C.  Results  obtained are presented i n Table 19 and F i g . 24. Thev.precipitated compound was analyzed and i t was found to correspond to the formula K 0.3A1 0 .4S0 .6H 0 (see App. I I ) . 2  gr/il  2  3  3  2  0  I  2  3  4  5  6  7  8  9  10  II  12  Fig. 2 3. HYDROLYSIS OF SODIUM-ALUMINIUM SULPHATE SOLUTION A T 2 2 5 C °  13  timeinhrs.  - 63 -  T a b l e 19.  H y d r o l y s i s o f aluminum s u l p h a t e - p o t a s s i u m at  Time at A l 225°C  sulphate  solution  225°C*  i n s o l SO,  i nsol  K i n sol Al  p r e c SO, p r e c 4  4  hrs  gr/£  gr/£  0  0.21  .24.06  1  o.oo •  23.54  2  0.00  3  0.00  K prec  pH  gr/£  gr/£  gr/£  5.91  14.08  2.855 0.69  1.51  6.12  14.60  2.955 0.67  23.56  1.51  6.12  14.58  2.955 0.66  23.54  1.51  6.12  14.60  2.955 0.66  Starting solution:  gr/Jt  1.61  38.14 gr/£ SO^" 6.12 g r / i l A l 4.465 gr/£ K pH = 3.09  When a l k a l i  metal  sulphate-aluminum s u l p h a t e s o l u t i o n s a r e  h y d r o l y z e d a t 225°C o n l y one s o l i d phase i w i t h the l i q u i d phase.  s  found  t o be i n e q u i l i b r i u m  The s o l i d phase corresponds  t o the formula 13  M 0.3A1 0 .4S0 6H 0. 2  2  3  3<  2  T h i s i s c o n t r a r y to the r e s u l t s o f V.S. S a z h i n .  I f t h e r e i s any temperature  limit  i n f o r m a t i o n o f M 0. 3 A 1 0 « 4S0.J. 6H 0 2  2  3  it  should be below 225°C and not 230°C.  in  such mixed s o l u t i o n s would be the b a s i c aluminum s u l p h a t e under  the c o n d i t i o n t h a t t h e r e i s Insufficient M  The most probable.second  +  2  phase  p r e s e n t i n the i n i t i a l  s o l u t i o n to p r e c i p i t a t e a l l aluminum i n the form of a l u n i t e . The  reaction  f o r • the hydrbthermal  p r e c i p i t a t i o n of alunites  can be w r i t t e n as ekl^  + 4HS0 " + 2M 4  +  + 12H.0 *• 2 -<  M 0.3A1.0 .4S0„.6H 0 + 16 H (13) 2 2 3 3 2 +  o  o  o  -  <  5.0  A  4.0 -  6  -  c n"t~:  o  «  k  D  0  *•  3.0 -  •  •  x -  0.0-  O (A  ^  o  36  3.0 -0.8 34  K  S 0  4  -  PH  32 -  2.0 -0.6 30 -  —  28 •  ON  4>-  1.0 -0.4 26 "•  V  -  \ ^o—o—o  1.0 -  pH  c  O Al  V  2.0 -  o •»  o  0 o «  _: v  \ \  OJO  -0.2 2 2 • 20  O v  ^•—o—o—o0  24  I  2  3  4  5 6  7  8  9  10  11  12  time in hrs.  Fig. 24. HYDROLYSIS OF POTASSIUM—ALUMINIUM SULPHATE SOLUTION AT 225 C°  - 65 -  The  e f f e c t of a l k a l i ,  y i e l d s are i n c r e a s e d  metal s u l p h a t e  s a l t s i s such t h a t the h y d r o l y s i s  i n the f o l l o w i n g s e r i e s K > Na > L i .  s e r i e s i s the same i f the i o n i c r a d i i of the L i , Na, Table Fig.  K are  20 shows the i o n i c r a d i i of the i o n s i n v o l v e d i n t h i s  compared.  system.  25 shows the s t r a i g h t l i n e r e l a t i o n between the i o n i c r a d i i  p r e c i p i t a t e d amount of aluminum i n h e a t i n g  Table  and  This  20.  Ionic r a d i i  Element  of the i o n s  Type of Radius  4.7  Ionic  the system to 225°C.  i n v o l v e d i n the  radius A°  Al  system  prec.  %  H  1  +  0.00  Al  3  +  0.57  Fe  3  Li  1  +  0.68  71.80  Fe  2  +  0.80  60.50  Cu  2  +  0.80  61.40  Na  1  +  0.98  83.00  K  1  +  1.33  96.80  The  and  48.00  0.67  +  E f f e c t of D i v a l e n t M e t a l Sulphates on H y d r o l y s i s  of  Aluminum Sulphate S o l u t i o n s at 225°C As with  a general  r u l e , i o n s of d i v a l e n t metals do not p r e c i p i t a t e  b a s i c aluminum s u l p h a t e .  p r e c i p i t a t e as o x i d e s ,  Many t r i v a l e n t or q u a d r i v a l e n t  metals  h y d r o x i d e s or b a s i c s a l t s under the same  - 66 -  - 67  -  c o n d i t i o n s as f o r h y d r o l y s i s of aluminum s u l p h a t e . copper  and i r o n was  presence  4.7.1  The  effect  i n v e s t i g a t e d a t 225°C m o s t l y because of  of  their  i n many l e a c h s o l u t i o n s .  The E f f e c t of Copper S u l p h a t e on H y d r o l y s i s of Aluminum Sulphate S o l u t i o n s at 225°C A  6.10  gr/£  copper- sulphate-aluminum s u l p h a t e s o l u t i o n c o n t a i n i n g aluminum, 3.58  h y d r o l y z e d at 225°C.  gr/£  copper  There was  T a b l e 21.  37.92 gr/£  p r a c t i c a l l y no  d e t e c t e d i n these experiments. T a b l e 21 and  and  SO^  copper  was  precipitation  R e s u l t s o b t a i n e d are p r e s e n t e d i n  F i g . 26.  H y d r o l y s i s of aluminum s u l p h a t e - c o p p e r  sulphate s o l u t i o n  at 225°C*  Time a t 225°C  Al in sol  Cu i n s o l  SO. i n s o l 4  Al  prec  Cu  prec  SO^  prec  pH  hrs.  gr/il  gr/Jl  gr/£  gr/jl  gr/£  0  2.35  3.56  29.02  3.75  0.02  8.90  0.94  1  1.48  3.58  26.92  4.62  0.00  11.00  0.85  2  1.23  3.57  26.32  4.87  0.01  11.60  0.82  4  1.12  3.56  26.06  4.98  0.02  11.86  0.82  6  1.10  3.58  26.06  5.00  0.00  11.86  0.82  Starting solution:  6.10  gr/£  Al  3.58  gr/£  Cu  37.92 gr/£ pH =  3.0  S0  4  gr/£  ON  00  I  0  I  2 3 4 5 6 7 8 9 10 I I 12 Fig.26. HYDROLYSIS OF COPPER-ALUMINIUM SULPHATE SOLUTION AT 2 2 5 C°  time in hrs.  -  4.7.2  69  -  The Effect of Ferrous Sulphate on Hydrolysis of Aluminum Sulphate Solutions at 225°C A  ferrous sulphate-aluminum sulphate solution  containing  6.12 gr/£ aluminum, 3-26 gr/SL iron and about 38.29 gr/£ SO^  -  hydrolyzed at 225°C.  Some iron was precipitated i n the form of ¥e^0^  due to atmospheric oxidation of ferrous i r o n . obtained i n this set of experiments 27.  was  Results  are presented i n Table 22 and F i g .  The increased p r e c i p i t a t i o n of aluminum can be attributed to the  common ion e f f e c t .  The bivalent ions are not compatible with the  alunite l a t t i c e and do not tend to replace the hydrogen ions i n basic 3 aluminum sulphate.. T.R. Scott  has reported that no contamination  of basic aluminum sulphate occurs i n the presence of Mg, Cd, Zn and Ni even at high concentrations. Table 22. Hydrolysis of aluminum sulphate-ferrous sulphate solution at 225°C* Time at A l i n s o l  Fe i n s o l  SO. i n s o l  hrs  gr/£  gr/£  gr/Jl  0  2.42  2.69  29.44  1  1.57  2.68  2  1.40  4 6  A l prec . gr/£  Fe prec  SO, prec  pH  gr/Jl  gr/Jl  3.70  0.57  8.85  0.97  27.48  4.55  0.58  10.81  0.82  2.69  27.04  4.72  0.57  11.25  0.80  1.15  2.66  26.42  4.97  0.60  11.87  0.82  1.12  2.69  26.40  5.00  0.57  11.89  0.80  Starting solution:  6.12 gr/£ A l ; 3.26 gr/l Fe; 38.29 gr/£ SO pH = 3.0  I8 -i  1  i  0  I  2  — J  3  1  i  4  5  '  6  «  7  »  8  9  Fig. 27 HYDROLYSIS OF IRON-ALUMINIUM SOLUTION AT 22 5C°  '  •  10  '  II  SULPHATE  •  12  '  '  '  time in hrs.  -  - 71 4.8  A p p l i c a t i o n of the H y d r o l y s i s P r o c e s s B a s i c aluminum s u l p h a t e of the form 3 A 1 0 . 4 S 0 . 9 H 0 i s the 2  3  3  2  product o f h i g h temperature h y d r o l y s i s o f aluminum s u l p h a t e s o l u t i o n s w i t h a wide range of i n i t i a l S O ^ A l ^  ratios.  A b a s i c s a l t of the  form M2O.3Al2O2.4sO2.6H2O i s a h i g h temperature h y d r o l y s i s p r o d u c t of aluminum s u l p h a t e s o l u t i o n s c o n t a i n i n g a l k a l i  metals  ( L i , Na or K ) .  Thermal decomposition o f such b a s i c s a l t s y i e l d s alumina as a f i n a l product which can be used f o r aluminum p r o d u c t i o n . t i o n of a few samples D.T.A.  Thermal  of b a s i c aluminum s u l p h a t e was  decomposi-  f o l l o w e d by  A t y p i c a l D.T.A. c u r v e i s shown i n F i g . 28.  The  first  endothermic peak i n the temperature range 200-400°C corresponds to the l o s s of i n t e r s t i t i a l l a t t i c e w a t e r . to  the d e h y d r o x y l a t i o n p r o c e s s .  temperatures  9  The peak a t about 450°C c o r r e s p o n d s  T h i s p r o c e s s i s completed  around 600°C where anhydrous  at  b a s i c aluminum s u l p h a t e  9 exists.  At temperatures  above 600°C, SO^,  y i e l d i n g amorphous alumina which at  h i g h e r temperatures.  SO2  Y Alumina  A few samples  6H2O were c a l c i n e d at about 1000°C f o r 2 h r s . f o l l o w e d by the weight l o s s .  2  of  K2O.3Al2O2.4SO2-  The decomposition of R e s u l t s of one of the  i s shown below.  1.0811 gr K 0 . 3 A 1 0 . 4 S 0 . 6 H 0 2  to y-alumina  i s t r a n s f o r m e d to a-alumina a t  -  decomposition experiments  are e v o l v e d  subsequently c r y s t a l l i z e s  temperatures of 1000°C and h i g h e r .  these samples was  and O2  3  3  0.5857 gr K 2 S 0 4 4- A 1 0 2  3  2  iffg^  > 0.5857 gr K S 0 2  4  + Al 0  +  , sulphurous t gases 0.365 gr A 1 0 2  3  o  200  400  Fig. 2 8 . D . T . A .  600 OF  3AI2O34SO39H2O  - 73 In leaching processes at high temperatures where aluminum i s present  i n solution i t p r e c i p i t a t e s as a basic s a l t i n autoclaves and  pipelines"'"''" which necessitates "forced" shutdowns of the process i n order to clean autoclaves acid concentration  and/or p i p e l i n e s .  and decreasing  With increasing sulphuric  temperature the s o l u b i l i t y of basic  aluminum sulphate was found to increase.  Therefore  running  concentrated  solutions of sulphuric acid through the system at low temperatures should dissolve the p r e c i p i t a t e . In dump leaching solutions aluminum i s present sulphate.  I f aluminum i s not recovered  w i l l increase.  as aluminum  the v i s c o s i t y of the solution  To remove the, aluminum from solution, a part of the  liquor after cementation can be treated i n an autoclave basic aluminum sulphate. recycled to the heap.  to p r e c i p i t a t e  Liberated acid from the hydrolysis can be  - 74 -  5.  1.  CONCLUSIONS  D i l u t e s o l u t i o n s of normal and a c i d aluminum s u l p h a t e h y d r o l y z e  when heated above 125°C  to y i e l d  a basic salt  of the nominal c o m p o s i t i o n  3A1 0 ,4S0 .9H 0. 2  2.  3  3  2  Hydrolysis  concentration  3.  yield  i s a f u n c t i o n of the temperature and  of s u l p h u r i c a c i d i n s o l u t i o n .  Only one s o l i d phase was  found to be i n e q u i l i b r i u m w i t h the  l i q u i d phase i n the temperature r e g i o n  125-250°C,  some i n d i c a t i o n s t h a t a l e s s b a s i c s a l t may  4.  but t h e r e are  e x i s t i n the system.  When L i , Na or K i o n s are p r e s e n t i n s o l u t i o n s of aluminum  s u l p h a t e a b a s i c s a l t of the form M 0 . 3 A 1 0 « 4 S 0 . 6 H 0 2  5.  initial  The h y d r o l y s i s y i e l d s are i n c r e a s e d  m e t a l s u l p h a t e s i n the f o l l o w i n g s e r i e s :  2  3  3  2  is precipitated.  i n the p r e s e n c e of a l k a l i K > Na > L i . I|  6.  Aluminum can be s e l e c t i v e l y p r e c i p i t a t e d i n the presence of Cu  and Fe" " " as 3 A 1 0 1  1  2  7.  Both  3 >  4S0 -9H 0. 3  2  b a s i c aluminum s u l p h a t e and a l u n i t e s can be c a l c i n e d a t  temperatures above 1000°C  to y i e l d  alumina.  - 75 -  APPENDIX I SOLUBILITY OF ALUMINUM SULPHATE  S o l u b i l i t y o f A l ( S O . K i n water  I-A  Temp. °C gr A 1 ( S 0 ) 2  4  30  40  50  60  70  26.7  28.8  31.4  34.3  37.2  39.8  Solubility sulpuric  gr  A1 (S0 ) 2  4  2  I-C  42.2  44.7  47.1  o f aluminum s u l p h a t e i n aqueous s o l u t i o n s of  a c i d a t 25°C.  27.82  sol.  0.0  Solubility  Temp. ° C  29. 21  26.2  19.5  11.6  4. 8  1. 5  1.0  2.3  4.0  5. 73  10.0  20.0  30.0  40. 0  50. 0  60.0  70.0  75.0  o f aluminum s u l p h a t e i n aqueous 10% H SO  30  A1 (S0 ) 2  100  4  100 g r s a t .  gr  90  3  100 g r s a t . s o l . gr H S 0  80  3  100 gr s a t . sol.  I-B  20  4  100 g r s a t .  42  50  3  sol.  14.52  16.45  18.77  -  76 -  APPENDIX I I ANALYSIS OF THE SOLID PHASES Time a t hrs.  Temp. C  6.00 10.00 16.30 4.0 6.0 18.00 1.00 5.00 16.00 0.00 1.00 3.30 6.30 6.00 6.00 6.00 6.00 6.00 4.00 4.00 4.00 4.00 4.00  175 175 175 200 200 200 225 225 225 250 250 250 250 225 225 225 225 . 225 250 250 250 250 250  % Al 0  38.7 38.5 38.7 38.6 38.8 38.7 38.8 38.9 39.1 38.8 38.7 39.0 39.2 39.0 . 38.7 38.9 38.9 39.2 38.9 38.8 38.9 39.2 38.9  % SO  % M0  % HO  Starting pH  37.2 39.6 39.7 39.5 39.9 40.1 40.2 40.8 41.6 40.3 40.2 40.5 40.9 40.6 40.6 40.8 40.2 41.7 40.6 40.7 41.2 41.6 40.8  -  24.1 21.9 21.6 21.9 21.3 21.2 21.0 20.3 19.3 20.9 21.1 20.05 19.9 20.4 20.7 20.3 20.9 19.1 20.5 20.5 19.9 19.20 20.3  3.10 3.10 3.10 3.10 3.10 3.10 3.10 3.10 3.10 3.10 3.10 3.10 3.10 2.5 2.0 1.5 1.0 0.70 2.5 2.0 1.5 1.0 0.70  14.10  3.05  13.80 13.50  3.09 3.09  13.20 12.80 13.10  3.09 3.09 3.09  0  Li 0 2  3.00  225  39.90  42.00  4.00 Na 0 2  2.00 8.00  225 225  38.40 38.50  40.10 40.20  7.70 7.80 K 0 2  0.00 0.00 1.00  225 225 225  37.05 36.91 37.12  38.39 38.91 38.48  11.36 11.38 11.30  - 77 APPENDIX I I I X-RAY DIFFRACTION PATTERNS III-A  D i f f r a c t i o n pattern of the p r e c i p i t a t e obtained at 150°C  Prec. obtained i n 10 hrs. d A° 5.71 5.03 3.55 3.01 2.27 1.909 1.76 1.654 1.566 1.496 1.325 1.290 1.220 1.171 1.150 III-B  o  Prec. obtained i n 16 hrs d A°  I/x  7 2 5 1 4 3 5 7 7 5 7 6 7 7 7  o  I/T  5.71 5.03 3.57 3.01 2.27 1.908 1.755 1.659 1.570 1.500 1.329 1.299 1.217 1.171 1.147  7 2 5 1 4 3 5 7 7 5 7 6 7 7 7  X-ray d i f f r a c t i o n patterns of the p r e c i p i t a t e obtained at 175  Prec. obtained i n 2 hrs. d A°  I/I  5.71 5.034 3.56 3.01  7 2 5 1  2.27  4  1.908 1.757 1.654 1.566 1.495  3 5 7 7 5  1.325 1.293 1.219 1.174 1.150  7 6 7 7 7  :  0  Prec. obtained i n 16.5 hrs d A° 5.75 5.12 3.56 3.04 2.87 2.486 2.30 2.22 1.920 1.770 1.654 1.570 1.500 1.380 1.330 .1.290 1.217 1.172 1.150  1 / T  o  1 2  5 1 7 8 4 8 3 5 7 7 5 8 7 6 7 7 7  - 78 -  III-C  X-ray d i f f r a c t i o n pattern of the p r e c i p i t a t e obtained at 200°C.  Prec. obtained i n 18 hrs. d  A°  .  5.72 5.03 3.56 3.04 2.87 2.27 2.22 1.910 1.756 1.654 1.565 1.490 1.387 1.290 1.217 1.171 1.151  III-D  I/I 7 2 5 1 7 4 8  3 •5 7 7 5 8 6 7 7 7  X-ray d i f f r a c t i o n pattern of the p r e c i p i t a t e obtained at 225°C Prec. obtained i n 3 hrs at 225°G d  A°  5.61 5.02 4.80 3.43 3.03 2.932 2.806 2.440 2.304 2.241 2.191 1.925 1.880 1.767 1.758  I 7 I  8 2 2 6 1 1 4 8 4 3 8 8 3 8 6  0  A°  I/I  1.736 1.666 1.641 1.550 1.546 1.479 1.4227 1.362 1.316 1.281 1.205 1.195 1.161 1.132  6 8 8 8 8 4 8 8 8 4 8 8 8 8  d  - 79 -  III-E  X-ray d i f f r a c t i o n p a t t e r n of the p r e c i p i t a t e obtained at 250°C  Prec. obtained i n 0.0 h r s . d A° 5.61 4.02 4.80 4.27 3.40 3.01 2.91 2.79 2.45 2.296 2.24 2.187 1.929 1.879  III-F  ^ 0 8 2 2 8 6 1 1 4 8 4 3 8 8 3  d A°  Prec. obtained i n 3.5 h r s . I / T  1.765 1.736 1.665 1.557 1.479 1.424 1.367 1.317 1.286 1.208 1.200 1.167 . 1.138  o  8 6 8 8 4 8 8 8 4 8 8 8 8  d A° 5.61 5.01 4.85 3.46 3.01 2.95 2.81 2.46 2.24 1.895  I / x  d A°  o  8 2 2  1.742 1.646 1.555 1.483 1.369 1.317 1.286 1.208 1.167 1.139  6 1 1 4 8 3 8  l / 1  o  6 8 4 8 8 4 8 8 8  X-ray d i f f r a c t i o n pattern of the p r e c i p i t a t e obtained from from FeSO -Al„(SO 4 2  s o l u t i o n at 225°C  Prec. obtained i n 4 . 0 h r s at 250°C d A° 5.08 4.80 3.03 2.915 2.294 2.234 1.918 1.888 1.768 1.737 1.637  1 / T  o  2 2 1  1 5 1 4 2 5 2 4  d A° 1.558 1.501 1.481 1.423 1.371 1.314 1.209 1.1969 1.1867 1.1364 1.1054  I/I 4 5 2 5 3 4 3 5 5 5 5  - 80 III-G  X-ray d i f f r a c t i o n pattern of potassium alunite obtained at 225°C Prec. obtained inO.Ohrs. at 225°C d A°  I/I 5 2 3 1 8 8 3 5 2 2 8  5.71 5.01 3.49 3.01 2.90 2.47 2.29 2.20 1.888 1.736 1.641  III-H.  I/I  1.560 1.546 1.489 1.422 1.380 1.316 1.281 1.205 1.161 1.132  8 8 3 8 8 8 5 5 6 6  r  X-ray d i f f r a c t i o n pattern of sodium alunite obtained at 225°C  Prec. obtained i n 2.0 d A° X  5.70 5.01 3.496 3.01 2.91 2.45 2.212 1.896  III-K  d A°  /  I  0  5 2 3 1 8 8 3 2  hrs. at 225°C d A° 1.746 1.644 1.554 1.538 1.505 1.281 1.205 1.161  2 8 8 8 3 5 5 6  X-ray d i f f r a c t i o n pattern of lithium alunite obtained at 225°C Prec. obtained i n 3.0 hrs. at 225°C d A° : 5.68 5.01 3.491 3.01 2.90 2.44 2.20 1.887  :  Wo  d A°  w„  5 2 3 1 8 8 3 2  1.736 1.641 1.554 1.535 1.489 1.281 1.205 1.161  2 8 8 8 3 5 5 6  - 81 LITERATURE 1.  E.T. Carlson, C.S. Simons, Met. Soc. of A.I.M.E., Extractive Metallurgy of Copper, Nickel and Cobalt.  International Symposium,  New York, February 15-18, 1960. 2.  Posnjak, E., Mervin, H.E., J . Am. Chem. Soc. 44, 1965-1994 (1929).  3.  P.T. Davey and T.R. Scott, Aust. J . Appl. S c i . 13, 229-241 (1962)  4.  Basset, H. and Goodwin, T.H., J . Chem. Soc., 2239-2279 (1949).  5.  T.R. Scott, Paper presented at the Annual Conference of the I n s t i t u t e , August 14-24, 19|>3, Melbourne.  6.  T.R. Scott, Extractive Metallurgy of Aluminum, V o l . 1, Alumina, International Symposium on the Extractive Metallury of Aluminum, February 18-22 (1962), New York.  7.  T.R. Scott, Research Appl. Ind. 14, 50-54 (1961).  8.  P.T. Davey and T.R. Scott, Nature 195, 376 (1962).  9.  P.T. Davey, G.M. Lukaszewski and T.R. Scott, Aust. J . Appl. S c i . 14, 137-154 (1963).  10.  Henry, J.L. and G.B. King, J . Am. Chem. Soc. 72_, 1282-1286 (1950).  11.  R. Acosta Chaves, V.V. K a r e l i n , and B.P. Sobolev, Tsvet. Met. 1968, 41 (4), 50.53.  12.  T.R. Scott, Internal Report, Division of Mineral Chemistry C.S.I.R.O.,  13.  Melbourne.  V.S. Sazhin, A.K. Zapolskii and N.N. Zakharova, Zh. P r i k l . Khim., 41 (7), 1420-1423 (1968).  14.  S. Bretsznajder, J . Boczar, J . P i s k o r s k i , and J . Porowski, Prezmysl. Chem. 11, 89-93 (1955).  15.  A.K. Zapolskii and G.I. Tsarenko, Ukr. Khim. Zh. 1969, 35 (8), 866-868.  - 82 16.  V.S. Sazhin, A.K. Z a p o l s k i i , N.N. Zakharova and A.I. Volkovska, Ukr. Khim. Zh. 1966, 32 (1), 95-100.  17.  A.K. Z a p o l s k i i , Ukr. Khim. Zh. 33 (8), 805-809 (1967).  18.  A.K. Z a p o l s k i i , V.S. Sazhin, N.N. Zakharova and A.I. Volkovska, Ukr. Khim. Zh. 32 (11), 1222-7 (1966).  19.  H.G.  Iverson and H. L e i t c h . Report of Investigations 7162 (1968).  20.  Erkki Wanninen and Anders Ringbom, Analytica Chimica Acta Vol. 12 (1955), 308-318.  21.  R.G. Robins, LR 80 (NST) Report of the Mineral S c i . and Technology Div. of the Warren Spring Laboratory.  22.  H.C. Helgeson, Am. J . of S c i . V o l . 267, 1969, 729-804.  

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