UBC Theses and Dissertations

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UBC Theses and Dissertations

Studies on the flotation depression of chalcopyrite, galena and sphalerite by thioglycollic acid Liu, Qi 1985

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STUDIES ON THE FLOTATION DEPRESSION OF CHALCOPYRITE, GALENA AND SPHALERITE BY THIOGLYCOLLIC ACID B.A.Sc. Wuhan I n s t . I & S Tech. (PRC), 1982 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF ' THE FACULTY OF GRADUATE STUDIES (Department of M i n i n g and M i n e r a l P r o c e s s E n g i n e e r i n g ) We a c c e p t t h i s t h e s i s as c o n f o r m i n g t o the r e q u i r e d s t a n d a r d THE UNIVERSITY OF BRITISH COLUMBIA Sep t . 1985 © L i u Q i , 1985 by MASTER OF APPLIED SCIENCE i n In p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t of the r e q u i r e m e n t s f o r an advanced degree a t t h e The U n i v e r s i t y of B r i t i s h C o l u m b i a , I a g r e e t h a t t h e L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and s t u d y . I f u r t h e r agree t h a t p e r m i s s i o n f o r e x t e n s i v e c o p y i n g of t h i s t h e s i s f o r s c h o l a r l y p u r p o s e s may be g r a n t e d by t h e Head of my Department or by h i s or her r e p r e s e n t a t i v e s . I t i s u n d e r s t o o d t h a t c o p y i n g or p u b l i c a t i o n of t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l not be a l l o w e d w i t h o u t my w r i t t e n p e r m i s s i o n . (Department of M i n i n g and M i n e r a l P r o c e s s E n g i n e e r i n g ) The U n i v e r s i t y of B r i t i s h C o l u m b i a 2075 Wesbrook P l a c e V a n c o u v e r , Canada V6T 1W5 D a t e : S e p t . 1985 i i ABSTRACT T h i o g l y c o l l i c a c i d (TGA) was found to e x h i b i t strong d e p r e s s i v e a c t i o n on c h a l c o p y r i t e , galena and s p h a l e r i t e samples. T h i s d e p r e s s i v e a c t i o n resembled hydrosulphide i n that the c o n t a c t curve of TGA was very s i m i l a r to that of sodium s u l p h i d e . An a d s o r p t i o n model was proposed based on the experimental o b s e r v a t i o n s . The model suggests t h a t TGA molecules adsorb onto s u l p h i d e m i n e r a l s u r f a c e s through e i t h e r t h e i r mercapto groups, or t h e i r c a r b o x y l groups, with subsequent m u l t i l a y e r a d s o r p t i o n of TGA onto t h i s chemisorbed l a y e r through hydrogen bonding and o x i d a t i v e dimer bonding. The TGA molecules adsorbed through the c a r b o x y l group were not r e s p o n s i b l e f o r the observed d e p r e s s i o n : these molecules were e a s i l y desorbed by potassium e t h y l xanthate. Oxygen was found to enhance the a d s o r p t i o n of TGA onto s u l p h i d e m ineral s u r f a c e s and consequently, to enhance the d e p r e s s i v e a c t i o n . The s e l e c t i v e s e p a r a t i o n of s y n t h e t i c s u l p h i d e m i n e r a l mixtures with the use of TGA has met l i m i t e d success. ACKNOWLEDGEMENT I w i s h t o e x p r e s s s i n c e r e a p p r e c i a t i o n t o Dr. G.W.Poling f o r h i s v a l u a b l e d i r e c t i o n and encouragement g i v e n t h r o u g h o u t the p e r i o d of s t u d y . A p p r e c i a t i o n i s a l s o e x t e n d e d t o Mrs. S . F i n o r a , Mr. A . A r a u j o , Mr. G. S e n i o r and o t h e r f a c u l t y members and s t u d e n t s i n the Dept. of MMPE f o r a s s i s t a n c e s and h e l p f u l d i s c u s s i o n s d u r i n g t h e e x p e r i m e n t a l and p r e p a r a t i o n of t h e t h e s i s . A s c h o l a r s h i p g r a n t e d by t h e M i n i s t r y of E d u c a t i o n , P e o p l e ' s R e p u b l i c of C h i n a i s g r a t e f u l l y acknowledged. iv T a b l e o f C o n t e n t s Page CHAPTER 1 INTRODUCTION 1 1.1 Review o f t h e L i t e r a t u r e 1 1.1.1 M a j o r S u l p h i d e D e p r e s s a n t s 1 1.1.2 D e p r e s s i v e Mechanisms of SH" and CN' 2 1.1.3 Drawbacks of I n o r g a n i c D e p r e s s a n t s 5 1.1.4 P r o p e r t i e s of TGA M o l e c u l e 8 1.1.5 D e p r e s s i v e Mechanisms o f T h i o g l y c o l l a t e 10 1.2 O b j e c t i v e o f T h i s I n v e s t i g a t i o n 12 CHAPTER 2 EXPERIMENTAL 13 2.1 M a t e r i a l 13 2.2 M i c r o f l o t a t i o n 18 2.2.1 H a l l i m o n d Tube F l o t a t i o n 18 2.2.2 P/S C e l l F l o t a t i o n 19 2.3 D e t e r m i n a t i o n of A d s o r p t i o n and D e s o r p t i o n 22 2.3.1 T h i o g l y c o l l i c A c i d 22 2.3.2 E t h y l X a n t h a t e 23 2.3.3 T e s t P r o c e d u r e 23 2.4 Zeta P o t e n t i a l Measurement 26 2.5 I d e n t i f i c a t i o n of R e a c t i o n P r o d u c t s 26 V T a b l e o f C o n t e n t s ( c o n t ' d ) Page 2.5.1 T r a n s m i t t a n c e S p e c t r a 26 2.5.2 A t t e n u a t e d T o t a l R e f l e c t a n c e S p e c t r a 27 CHAPTER 3 EXPERIMENTAL RESULTS 30 3.1 Predominant S p e c i e s i n TGA S o l u t i o n 30 3.2 S t o i c h i o m e t r y o f T h i o g l y c o l l a t e S a l t F o r m a t i o n 32 3.3 D e p r e s s i v e A c t i o n of TGA on S u l p h i d e M i n e r a l s 35 3.4 A d s o r p t i o n of TGA and Removal of A d s o r b e d E t h y l X a n t h a t e 40 3.5 E f f e c t of Oxygen on the A d s o r p t i o n of TGA ..50 3.6 Z e t a P o t e n t i a l s of M i n e r a l s .57 3.7 S o l u t i o n Redox P o t e n t i a l and M i n e r a l F l o a t a b i l i t y 61 3.8 I n f r a r e d S p e c t r a 73 3.8.1 S p e c t r a o f M e t a l T h i o g l y c o l l a t e s ...73 3.8.2 S p e c t r a o f C h a l c o p y r i t e 76 3.8.3 S p e c t r a o f S y n t h e t i c ZnS 78 3.8.4 S p e c t r a of G a l e n a 78 3.8.5 R e f l e c t a n c e S p e c t r a 85 3.8.6 M i s c e l l a n e o u s S p e c t r a 88 3.9 D i f f e r e n t i a l F l o t a t i o n of S y n t h e t i c M i n e r a l M i x t u r e s 88 CHAPTER 4 DISCUSSION 97 4.1 S t r u c t u r e of T h i o g l y c o l l a t e S a l t 97 v i T a b l e of C o n t e n t s ( c o n t ' d ) Page 4.2 A d s o r p t i o n Mechanisms of TGA 99 4.2.1 D e p r e s s i v e - R e s p o n s i b l e S p e c i e s of TGA 99 4.2.2 A d s o r p t i o n of TGA 101 4.3 E f f e c t of Oxygen 102 4.4 S e l e c t i v i t y 103 CHAPTER 5 CONCLUSION 104 REFERENCE 107 APPENDIX I Kodak I r t r a n I I M a t e r i a l 110 APPENDIX I I C o n d i t i o n s of I o d i n e T i t r a t i o n of TGA 113 APPENDIX I I I P o u r b a i x Diagrams of t h e Copper-Water System and t h e Lead-Water System 118 v i i L i s t of T a b l e s Page T a b l e I . T o x i c i t y d a t a of s e v e r a l s u l p h i d e d e p r e s s a n t s , 7 T a b l e I I M i n e r a l samples 17 T a b l e I I I S t o i c h i o m e t r y of the R e a c t i o n Between TGA and Copper o r Lead Ions 36 T a b l e A1 R e f r a c t i v e i n d i c e s - Kodak i n f r a r e d o p t i c a l m a t e r i a l s 112 T a b l e A2 I n d i c e s of r e f r a c t i o n f o r I r t r a n m a t e r i a l s -base ind e x and c o e f f i c i e n t s 112 v i i i L i s t of F i g u r e s Page F i g . 1 Contact, c u r v e s of sodium s u l p h i d e , [KEX]=25mg/l. E x t r a c t e d from r e f e r e n c e [8] 4 F i g . 2 D i s s o c i a t i o n of sodium s u l p h i d e ; d a t a e x t r a c t e d from r e f e r e n c e [ 8 ] , c o n c e n t r a t i o n of S 2 ' i g n o r e d 4 F i g . 3 R e l a t i o n s between c h a l c o p y r i t e f l o t a t i o n and redox p o t e n t i a l of the p u l p 6 F i g . 4 S c h e m a t i c d i a g r a m of the e l u t r i a t o r used f o r p r e t r e a t m e n t of s u l p h i d e m i n e r a l samples 14 F i g . 5 a S c h e m a t i c d i a g r a m of the P/S c e l l m o d i f i e d w i t h f o u r e l e c t r o d e s f o r t h e s i m u l t a n e o u s measurements of pH, oxygen c o n c e n t r a t i o n and redox p o t e n t i a l of t h e f l o t a t i o n p u l p 20 F i g . 5 b The m o d i f i e d P/S c e l l a t work 20 F i g . 6 B e e r ' s law f o r p o t a s s i u m e t h y l x a n t h a t e u s i n g a 1 cm q u a r t z c e l l ( a t 301 nm) 24 F i g . 7 A d s o r p t i o n / d e s o r p t i o n t e s t p r o c e d u r e 25 F i g . 8 O p t i c a l p a t h of the m u l t i p l e i n t e r n a l r e f l e c t i o n a ttachment 29 F i g . 9 T i t r a t i o n c u r v e of t h i o g l y c o l l i c a c i d , TGA: 0.01M, 100 m l ; NaOH: 0.102M 31 i x L i s t of F i g u r e s ( c o n t ' d ) Page F i g . 1 0 I o d i n e t i t r a t i o n of s t o c k e d t h i o g l y c o l l i c a c i d s o l u t i o n , 0.005N I 2 / l ml 0.01m s t o c k e d s o l u t i o n 33 F i g . 1 1 D i s s o c i a t i o n of t h i o g l y c o l l i c a c i d , d i s s o c i a t i o n c o n s t a n t : 2.51x10"" 34 F i g . 1 2 H a l l i m o n d tube f l o t a t i o n of c h a l c o p y r i t e t r e a t e d w i t h p o t a s s i u m e t h y l x a n t h a t e and t h i o g l y c o l l i c a c i d .......37 F i g . 1 3 H a l l i m o n d tube f l o t a t i o n of g a l e n a t r e a t e d w i t h p o t a s s i u m e t h y l x a n t h a t e and t h i o g l y c o l l i c a c i d 38 F i g . 1 4 H a l l i m o n d tube f l o t a t i o n of C u - a c t i v a t e d s p h a l e r i t e t r e a t e d w i t h p o t a s s i u m e t h y l x a n t h a t e and t h i o g l y c o l l i c a c i d 39 F i g . 1 5 D e p r e s s i v e a c t i o n of t h i o g l y c o l l i c a c i d on c h a l c o p y r i t e 41 F i g . 1 6 D e p r e s s i v e a c t i o n of t h i o g l y c o l l i c a c i d on g a l e n a 42 F i g . 1 7 D e p r e s s i v e a c t i o n of ammonium t h i o g l y c o l l a t e on c h a l c o p y r i t e 43 F i g . 1 8 D e p r e s s i v e a c t i o n of g l y c o l l i c a c i d (GA) and t h i o g l y c o l l i c a c i d (TGA) on c h a l c o p y r i t e 44 F i g . 1 9 D e p r e s s i v e a c t i o n of g l y c o l l i c a c i d (GA) and t h i o g l y c o l l i c a c i d (TGA) on g a l e n a ..45 X L i s t of F i g u r e s ( c o n t ' d ) Page F i g . 2 0 A d s o r p t i o n of t h i o g l y c o l l i c a c i d on c h a l c o p y r i t e and c o r r e s p o n d i n g removal of a d s o r b e d e t h y l x a n t h a t e 46 F i g . 2 1 A d s o r p t i o n of t h i o g l y c o l l i c a c i d on C u - a c t i v a t e d s p h a l e r i t e and c o r r e s p o n d i n g removal of a d s o r b e d e t h y l x a n t h a t e 47 F i g . 2 2 A d s o r p t i o n of t h i o g l y c o l l i c a c i d on g a l e n a and c o r r e s p o n d i n g removal of a d s o r b e d e t h y l x a n t h a t e 48 F i g . 2 3 C o n c e n t r a t i o n of r e a c t i o n p r o d u c t as a f u n c t i o n of c o n t a c t t i m e a t a e r a t e d c o n d i t i o n ( c h a l c o p y r i t e ) 51 F i g . 2 4 C o n c e n t r a t i o n of r e a c t i o n p r o d u c t as a f u n c t i o n of c o n t a c t t i m e under n i t r o g e n atmosphere ( c h a l c o p y r i t e ) 52 F i g . 2 5 C o n c e n t r a t i o n of r e a c t i o n p r o d u c t as a f u n c t i o n of c o n t a c t t i m e a t a e r a t e d c o n d i t i o n ( g a l e n a ) '. . 53 F i g . 2 6 C o n c e n t r a t i o n of r e a c t i o n p r o d u c t as a f u n c t i o n of c o n t a c t t i m e under n i t r o g e n atmosphere ( g a l e n a ) 54 F i g . 2 7 C o n c e n t r a t i o n of r e a c t i o n p r o d u c t as a f u n c t i o n of c o n t a c t t i m e a t a e r a t e d c o n d i t i o n ( s p h a l e r i t e ) 55 F i g . 2 8 C o n c e n t r a t i o n of r e a c t i o n p r o d u c t as a f u n c t i o n of c o n t a c t t i m e under n i t r o g e n atmosphere ( s p h a l e r i t e ) 56 F i g . 2 9 Z e t a p o t e n t i a l s of c h a l c o p y r i t e 58 L i s t of F i g u r e s ( c o n t ' d ) x i Page F i g . 3 0 Z e t a p o t e n t i a l s of g a l e n a 59 F i g . 3 1 Z e t a p o t e n t i a l s of s p h a l e r i t e 60 F i g . 3 2 E f f e c t of pH on t h e s o l u t i o n redox p o t e n t i a l and c o r r e s p o n d i n g c h a l c o p y r i t e f l o t a t i o n ( t h i o g l y c o l l i c a c i d as d e p r e s s a n t ) 62 F i g . 3 3 E f f e c t of pH on t h e s o l u t i o n redox p o t e n t i a l s and c o r r e s p o n d i n g c h a l c o p y r i t e f l o t a t i o n ( p o t a s s i u m c y a n i d e as d e p r e s s a n t ) 63 F i g . 3 4 E f f e c t of pH on t h e s o l u t i o n redox p o t e n t i a l and c o r r e s p o n d i n g c h a l c o p y r i t e f l o t a t i o n ( s odium s u l p h i d e as d e p r e s s a n t ) 64 F i g . 3 5 Redox p o t e n t i a l s of 0.001M t h i o g l y c o l l i c a c i d s o l u t i o n 65 F i g . 3 6 Redox p o t e n t i a l s of 0.001M p o t a s s i u m c y a n i d e s o l u t i o n 66 F i g . 3 7 Redox p o t e n t i a l s of 0.001M sodium s u l p h i d e s o l u t i o n 67 F i g . 3 8 E f f e c t of pH on t h e s o l u t i o n redox p o t e n t i a l s and c o r r e s p o n d i n g c h a l c o p y r i t e f l o t a t i o n , t h i o g l y c o l l i c a c i d as d e p r e s s a n t s , a l l samples x a n t h a t e d i n a e r a t e d s o l u t i o n s 69 F i g . 3 9 E f f e c t of pH on t h e s o l u t i o n redox p o t e n t i a l s and c o r r e s p n o d i n g g a l e n a f l o t a t i o n , t h i o g l y c o l l i c a c i d as d e p r e s s a n t , samples x a n t h a t e d i n a e r a t e d s o l u t i o n s 70 X l l L i s t of F i g u r e s ( c o n t ' d ) Page F i g . 4 0 E f f e c t of pH on t h e s o l u t i o n redox p o t e n t i a l and c o r r e s p n o d i n g s p h a l e r i t e f l o t a t i o n , t h i o g l y c o l l i c a c i d as d e p r e s s a n t , samples x a n t h a t e d i n a e r a t e d s o l u t i o n s 71 F i g . 4 1 E f f e c t of x a n t h a t i o n c o n d i t i o n on c h a l c o p y r i t e f l o t a t i o n 72 F i g . 4 2 I n f r a r e d s p e c t r a of (a) c h a l c o p y r i t e , (b) g a l e n a , (c) copper s u l p h a t e , (d) l e a d s u l p h a t e , (e) q u a r t z KBr p e l l e t s 74 F i g . 4 3 I n f r a r e d s p e c t r a of (a) copper t h i o g l y c o l l a t e (KBr p e l l e t ) , (b) l e a d t h i o g l y c o l l a t e (KBr p e l l e t ) , (c) TGA (NaCl c e l l ) , (d) DTGA ( o x i d i z e d by i o d i n e , N a C l c e l l ) , (e) d e u t e r i z e d TGA (NaCl c e l l ) 75 F i g . 4 4 I n f r a r e d s p e c t r a of c h a l c o p y r i t e (a) n o r m a l , (b) t r e a t e d w i t h KEX (pH 6.3), (c) t r e a t e d w i t h KEX (pH 6.3), t h e n w i t h TGA (pH 6.3), (d) t r e a t e d w i t h KEX (pH 6.3), then w i t h TGA (pH 11.5). (e) r e f e r e n c e s p e c t r u m of CuEX+(EX) 2. ( f ) r e f e r e n c e s p e c t r u m of copper t h i o g l y c o l l a t e . KBr p e l l e t s 77 F i g . 4 5 I n f r a r e d s p e c t r a of c h a l c o p y r i t e (a) n o r m a l , (b) t r e a t e d w i t h TGA (pH 5.2), (c) t r e a t e d w i t h TGA (pH 5.2), t h e n w i t h KEX (pH 6.2). (d) r e f e r e n c e s p e c t r u m of cop p e r t h i o g l y c o l l a t e . (e) r e f e r e n c e s p e c t r u m of CuEX+(EX) 2. KBr p e l l e t s 79 F i g . 4 6 I n f r a r e d s p e c t r a of (a) s y n t h e t i c ZnS, and C u - a c t i v a t e d s y n t h e t i c ZnS t r e a t e d (b) w i t h KEX (pH 6.3), (c) w i t h KEX (pH 6.3), then w i t h TGA (pH 6.3), (d) w i t h KEX (pH 6.3), then w i t h TGA (pH 11.9). (e) r e f e r e n c e s p ectrum of CuEX+(EX) 2. ( f ) r e f e r e n c e spectrum of copper t h i o g l y c o l l a t e . • KBr p e l l e t s 80 L i s t of F i g u r e s ( c o n t ' d ) Page F i g . 4 7 I n f r a r e d s p e c t r a of (a) s y n t h e t i c ZnS, and C u - a c t i v a t e d ZnS t r e a t e d (b) w i t h TGA (pH 7.5), ( c ) w i t h TGA (pH 7.5), then w i t h KEX (pH 7.5). (d) r e f e r e n c e s p e c t r u m of copper t h i o g l y c o l l a t e , (e) r e f e r e n c e spectrum of CuEX+(EX) 2. KBr p e l l e t s . 81 F i g . 4 8 I n f r a r e d s p e c t r a of g a l e n a (a) n o r m a l , (b) t r e a t e d w i t h KEX (pH 6.6), (c) t r e a t e d w i t h KEX (pH 6.6), then w i t h TGA (pH 6.6), (d) t r e a t e d w i t h KEX (pH 6.6), then w i t h TGA(pH 9.8). (e) r e f e r e n c e s p e c t r u m of l e a d e t h y l x a n t h a t e . ( f ) r e f e r e n c e spectrum of l e a d t h i o g l y c o l l a t e . KBr p e l l e t s 82 F i g . 4 9 I n f r a r e d s p e c t r a of g a l e n a (a) n o r m a l , (b) t r e a t e d w i t h TGA (0.01M, pH 5 ) , (c) t r e a t e d w i t h TGA (0.01M, pH 5 ) , then w i t h KEX (0.001M, pH 5.2). (d) r e f e r e n c e s p e c t r u m of l e a d t h i o g l y c o l l a t e . (e) r e f e r e n c e spectrum of l e a d e t h y l x a n t h a t e . KBr p e l l e t s 84 F i g . 5 0 I n f r a r e d s p e c t r a of ZnS p r i s m t r e a t e d w i t h p o t a s s i u m e t h y l x a n t h a t e , t h e n w i t h t h i o g l y c o l l i c a c i d . ATR 86 F i g . 5 1 I n f r a r e d s p e c t r a of (a) CuEX+(EX) 2 (KBr p e l l e t ) , and ZnS p r i s m a c t i v a t e d by Cu, c o n d i t i o n e d w i t h TGA f o r 4 hours and then r e a c t e d w i t h KEX f o r (b) 1 hour, (c) 4 hou r s a t pH 6. ATR 87 F i g . 5 2 I n f r a r e d s p e c t r a of co p p e r t h i o g l y c o l l a t e (a) n o r m a l , and t r e a t e d w i t h 0.001M KEX a t pH 6.5 f o r (b) 10 m i n u t e s , ( c ) 30 minutes and (d) 60 m i n u t e s , (e) r e f e r e n c e spectrum of CuEX+(EX) 2. KBr p e l l e t s 89 xiv L i s t of F i g u r e s ( c o n t ' d ) Page F i g . 5 3 I n f r a r e d s p e c t r a of (a) CuEX+(EX) 2, (b) CuEX+(EX) 2 r e a c t e d w i t h 0.001M TGA s o l u t i o n f o r 60 m i n u t e s a t pH 3.5. KBr p e l l e t 90 F i g . 5 4 F l o t a t i o n s e p a r a t i o n of s y n t h e t i c c h a l c o p y r i t e - g a l e n a m i x t u r e s w i t h t h i o g l y c o l l i c a c i d 91 F i g . 5 5 F l o t a t i o n s e p a r a t i o n of s y n t h e t i c c h a l c o p y r i t e - g a l e n a m i x t u r e s w i t h p o t a s s i u m c y a n i d e 92 F i g . 5 6 F l o t a t i o n s e p a r a t i o n of s y n t h e t i c c h a l c o p y r i t e - g a l e n a m i x t u r e s w i t h sodium s u l p h i d e 93 F i g . 5 7 F l o t a t i o n s e p a r a t i o n of s y n t h e t i c m i x t u r e s of c h a l c o p y r i t e and C u - a c t i v a t e d s p h a l e r i t e .94 F i g . 5 8 F l o t a t i o n s e p a r a t i o n of s y n t h e t i c m i x t u r e s of c h a l c o p y r i t e and s p h a l e r i t e a c t i v a t e d w i t h 10" 5M copper s u l p h a t e s o l u t i o n 95 F i g . 5 9 F l o t a t i o n s e p a r a t i o n of s y n t h e t i c m i x t u r e s of c h a l c o p y r i t e and s p h a l e r i t e a c t i v a t e d w i t h 2 x l 0 _ a M copper s u l p h a t e s o l u t i o n 96 F i g . 6 0 C o n t a c t c u r v e o f t h i o g l y c o l l i c a c i d 100 F i g . 6 1 S c hematic d i a g r a m of t h e p o s s i b l e a d s o r p t i o n model of t h i o g l y c o l l i c a c i d onto s u l p h i d e m i n e r a l s u r f a c e 100 F i g . A I Tra'nsmittance c u r v e s of I r t r a n I I m a t e r i a l 112 XV L i s t of F i g u r e s ( c o n t ' d ) Page F i g . A 2 R e d u c t i o n of d i t h i o d i g l y c o l l i c a c i d w i t h z i n c m e t a l 115 F i g . A 3 E f f e c t of pH v a l u e of TGA s o l u t i o n on i o d i n e t i t r a t i o n 117 F i g . A 4 P o t e n t i a l - p H d i a g r a m of t h e w a t e r - c o p p e r system 119 F i g . A 5 P o t e n t i a l - p H d i a g r a m of t h e w a t e r - l e a d system ..120 1 CHAPTER 1 INTRODUCTION In 1948, G i b b s p a t e n t e d t h e use of a s e r i e s of o r g a n i c compounds as s e l e c t i v e s u l p h i d e d e p r e s s a n t s [1].' They were mercapto c a r b o x y l i c a c i d s , HS-R-COOH, and a s i m i l a r t y p e , mercapto t h i o l i c a c i d s , HS-R-COSH; where R r e p r e s e n t e d an o r g a n i c g r o u p , p r e f e r a b l y a s a t u r a t e d a l i p h a t i c group [ 1 ] . These d e p r e s s a n t s were not used u n t i l r e c e n t l y . The s i m p l e s t form of them, t h i o g l y c o l l a t e ( H S C H 2 C O O H ) , has been used i n Bagdad Copper, A r i z o n a f o r about f i v e y e a r s [ 2 ] [ 3 ] . Noranda Mines L t d . i s a l s o r e p o r t e d t o have used t h i s t h i o g l y c o l l a t e a t Boss M o u n t a i n [ 4 ] , In s p i t e of the s u c c e s s i n p l a n t p r a c t i c e , l i t t l e i s known about t h e d e p r e s s i v e mechanisms i n v o l v e d . 1 .1 Review of t h e L i t e r a t u r e 1.1.1 M a j o r S u l p h i d e D e p r e s s a n t s Over t h e y e a r s , a few i n o r g a n i c r e a g e n t s have been r o u t i n e l y used as s u l p h i d e d e p r e s s a n t s . For example, s u l p h i t e and chromate a r e used f o r t h e d e p r e s s i o n of g a l e n a ; s u l p h i t e and z i n c s u l p h a t e f o r s p h a l e r i t e and f i n a l l y , c y a n i d e i s used f o r c o p p e r , z i n c and i r o n s u l p h i d e s [ 5 ] . A r s e n i c a l Nokes, a m i x t u r e of a r s e n i c t r i o x i d e and sodium s u l p h i d e , and Nokes r e a g e n t , phosphorous p e n t a s u l p h i d e d i s s o l v e d i n sodium h y d r o x i d e , a r e c o p p e r s u l p h i d e d e p r e s s a n t s [ 6 ] . Sodium s u l p h i d e ( o r sodium h y d r o s u l p h i d e ) i s w e l l known t o be d e p r e s s a n t f o r a l l s u l p h i d e s [ 5 ] . In t h e copper-molybdenum f l o t a t i o n s e p a r a t i o n c i r c u i t , where the t h i o g l y c o l l a t e has r e p l a c e d i n o r g a n i c s i n some p l a n t s , t h e predominant scheme i s t o d e p r e s s t h e copper s u l p h i d e s w h i l e c a p i t a l i z i n g on t h e ready f l o a t a b i l i t y of m o l y b d e n i t e t o e f f e c t the s e p a r a t i o n . C y a n i d e i s u s u a l l y added t o t h e p u l p i f t h e main copper s u l p h i d e i s c h a l c o p y r i t e , whereas f e r r o c y a n i d e i s used i f c h a l c o c i t e i s the major copper m i n e r a l . Some form of s u l p h i d e whether as sodium s u l p h i d e , h y d r o s u l p h i d e o r phosphorous p e n t a s u l p h i d e i s used when t h e r e i s a m i x t u r e of copper s u l p h i d e s [ 4 ] . O n l y i n a few c a s e s i s t h e s e p a r a t i o n e f f e c t e d by d e p r e s s i n g t h e m o l y b d e n i t e w i t h v a r i o u s p o l y m e r s , w h i l e a l l o w i n g copper s u l p h i d e t o f l o a t [ 7 ] . 1.1.2 D e p r e s s i v e Mechanisms of SH' and CN~ H y d r o s u l p h i d e a n i o n , SW, and c y a n i d e a n i o n , CN", a r e t h e two main d e p r e s s i v e s p e c i e s f o r s u l p h i d e m i n e r a l s . Sodium s u l p h i d e i s a w e l l - known s u l p h i d e d e p r e s s a n t . A c o n t a c t c u r v e i n F i g . 1 shows t h a t i t s d e p r e s s i v e a c t i o n i n c r e a s e s r a p i d l y w i t h i n c r e a s e i n pH. E x a m i n a t i o n of the d i s s o c i a t i o n c u r v e of sodium s u l p h i d e ( F i g . 2) shows t h a t SH" i s t h e o n l y a c t i v e d e p r e s s i v e s p e c i e s i n sodium s u l p h i d e s o l u t i o n a t pH's g r e a t e r t h a n 9. In t h e i r r e c e n t r e v i e w , P o l i n g and B e a t t i e [9] have summarized the d e p r e s s i v e mechanisms of a range of d e p r e s s a n t s f o r s u l p h i d e m i n e r a l s . They c o n s i d e r e d t h a t b o t h SH _ and CN" d e p r e s s e d the s u l p h i d e m i n e r a l s by d i s p l a c i n g t h e c o l l e c t o r c o a t i n g from the m i n e r a l s u r f a c e . In a d d i t i o n , c y a n i d e can l e a c h c h e m i c a l l y some m e t a l i o n s from the m i n e r a l s u r f a c e , and can a l s o form h y d r o p h i l i c m e t a l c y a n i d e complexes which remain a d s o r b e d on t h e s u r f a c e s . In a d d i t i o n t o t h e above c h e m i c a l a s p e c t of t h e d e p r e s s i o n , an e l e c t r o c h e m i c a l model was a l s o p r o p o s e d . F i r s t , i t was n o t e d t h a t t h e p o t e n t i a l of a c o p p e r e l e c t r o d e immersed i n c y a n i d e s o l u t i o n s a t v a r i o u s pHs m i r r o r e d t h e b u b b l e - m i n e r a l c o n t a c t c u r v e s , which i n d i c a t e d a d e f i n i t e c o r r e l a t i o n between the e l e c t r o d e p o t e n t i a l and t h e p r e v e n t i o n of a d s o r p t i o n of x a n t h a t e by c h a l c o p y r i t e [ 8 ] , I t was w e l l documented r e c e n t l y t h a t t h e a d s o r p t i o n of t h i o t y p e c o l l e c t o r s onto s u l p h i d e m i n e r a l s u r f a c e s i s an e l e c t r o c h e m i c a l p r o c e s s i n v o l v i n g e l e c t r o n t r a n s f e r [ 1 0 ] . The a d d i t i o n of r e a g e n t s w h i c h i n h i b i t t h i s e l e c t r o n t r a n s f e r w i l l t h e r e f o r e p r e v e n t a d s o r p t i o n of c o l l e c t o r , t h u s d e p r e s s i n g t h e m i n e r a l . The m a j o r i t y of t h e s u l p h i d e d e p r e s s a n t s , i n c l u d i n g SH~ and CN", have been found t o be 120 Contact curves of sodium sulphide, [KEX]=25mg/l. Extracted from reference [ 8 1• 11 12 Dissociation of sodium sulphide, data extracted from reference [ 8 ] . Concentration of S ignored. r e d u c i n g a g e n t s [ 7 ] , J a n e t s k i , Woodburn and Woods [11] have shown t h a t a d d i t i o n of sodium s u l p h i d e p r e v e n t e d the f o r m a t i o n of d i x a n t h o g e n on p y r i t e i n an oxygenated x a n t h a t e s o l u t i o n and t h e p y r i t e was d e p r e s s e d ; the a c t u a l e l e c t r o c h e m i c a l p r o c e s s i n the s o l u t i o n was t h e o x i d a t i o n of SH~ i o n s and r e d u c t i o n of oxygen. Agar et a l [12] w o r k i n g on the d e p r e s s i o n of c h a l c o p y r i t e by KCN i n an a e r a t e d x a n t h a t e s o l u t i o n , have found t h a t i t was the p o t e n t i a l of t h e s o l u t i o n r a t h e r than t h e l e v e l of KCN which d e t e r m i n e d t h e f l o t a t i o n r e c o v e r y of c h a l c o p y r i t e (see F i g . 3 ) . 1.1.3 Drawbacks of I n o r g a n i c D e p r e s s a n t s Almost a l l of t h e i n o r g a n i c d e p r e s s a n t s mentioned so f a r a r e p o t e n t i a l l y t o x i c . T a b l e I p r e s e n t s a l i s t of t o x i c i t y d a t a , i n c l u d i n g t h o s e of t h i o g l y c o l l a t e . These d a t a i n d i c a t e t h a t o n l y s u l p h i d e and t h i o g l y c o l l a t e a r e r e l a t i v e l y n o n - t o x i c * I t i s u n d e r s t a n d a b l e t h a t t h e i n c r e a s i n g h e a l t h and e n v i r o n m e n t a l r e s t r i c t i o n s a r e l i m i t i n g t h e use of t h e i n o r g a n i c r e a g e n t s . As m e n t i o n e d b e f o r e , i t has been shown r e c e n t l y t h a t most of t h e e f f e c t i v e d e p r e s s a n t s f o r copper s u l p h i d e s a r e s t r o n g l y r e d u c i n g , p a r t i c u l a r l y s u l p h i d e and h y d r o s u l p h i d e [ 7 ] . T h i s f i n d i n g h e l p e d i n u n d e r s t a n d i n g t h e d e p r e s s i v e mechanism s i n c e the a d s o r p t i o n of x a n t h a t e on s u l p h i d e * T o x i c i t y d a t a on TGA a r e s p a r s e (see T a b l e I ) . S i n c e TGA has been used as an a c t i v e i n g r e d i e n t i n cold-wave permanent h a i r d r e s s i n g s , i t can be s a f e l y assumed t h a t TGA i s r e l a t i v e l y n o n - t o x i c . 6 100 200 340 210 320 . 9*0 400 REDOX POTENTIAL, - m V O0.1S t/K« N « C N O0.30 " •• V Jmta «*«4iti*fti»« • 0.4J - - J V0.4S •• " 3wia «*«4M«i»i«« A 0.4S " lOmia «»»JilUm«»« Fig. 3 Relations Between Chalcopyrite Flotation and Redox Potential of the Pulp (12 ]. 7 Table I Toxicity Data of Several Sulphide Depressants ( From reference [13 ] and [ 1 4 ] ) --^reagent ind ex TGA KCN Na 2S A s 2 0 3 P 2 S 5 Na oCr0. 2 4 * o r l - r a t LD^^ 250 10 & N.A. 45 389 N.A. ** TLV N.A. 5 N.P*& 0.5(As) 1 0.1(CrO 3)* *** TLm N.A. 0 . 1 6 " 6 l " 5.3 @ N.A. 300 L L * L D 5 Q : L e t h a l Dose 50% k i l l , mg/kg. ** Threshold L i m i t Value: the concentration of an airborne constituent to which workers may be exposed repeatedly, 3 day by day without adverse e f f e c t , mg/m . ***Medium Tolerance L i m i t : 50% of the species studied show abnormal behaviour ( i n c l u d i n g death) within the period of study, ppm. & Not A v a i l a b l e . && Not P e r t i n e n t . // P o s s i b l y cause lung cancer. iHt B l u e g i l l , 48 hours. @ Salmon, 8 days. @@ B l u e g i l l , 24 hours. s u r f a c e s i s c o n s i d e r e d as an e l e c t r o c h e m i c a l p r o c e s s [ 1 0 ] . S t u d i e s a l s o r e v e a l e d t h a t t h e w a s t e f u l consumption of d e p r e s s a n t s t h r o u g h o x i d a t i o n i n a e r a t e d p u l p was i n e v i t a b l e . T h i s e x p l a i n e d t h e h i g h consumption of some d e p r e s s a n t s . I n r e c e n t y e a r s , a few copper-molybdenum s e p a r a t i o n p l a n t s have s t a r t e d u s i n g n i t r o g e n i n t h e i r f l o t a t i o n c i r c u i t s t o m i n i m i z e t h e l o s s of h y d r o s u l p h i d e [ 1 5 ] [ 1 6 ] . At t h i s p o i n t i t becomes c l e a r why t h i o g l y c o l l a t e , o r a d e r i v a t i v e , has s p u r r e d g r e a t i n t e r e s t , t h i r t y y e a r s a f t e r t h e d i s c o v e r y of i t s d e p r e s s i v e a c t i o n . A l t h o u g h t h i o g l y c o l l a t e i s more e x p e n s i v e t h a n i n o r g a n i c d e p r e s s a n t s [ 3 ] , t h e a d d i t i o n a l c o s t r e q u i r e d t o t r e a t t h e waste water when c y a n i d e i s used, and t h e h i g h e r c onsumption when s u l p h i d e o r h y d r o s u l p h i d e i s used might j u s t i f y t h e use of t h i s o r g a n i c d e p r e s s a n t . T h i o g l y c o l l a t e i s a l s o r e a d i l y o x i d i z e d , but t h e o x i d i z e d form can s t i l l be an e f f e c t i v e d e p r e s s a n t . I t has been r e p o r t e d t h a t t h e amount r e q u i r e d t o a c h i e v e t h e same d e p r e s s i o n was s i g n i f i c a n t l y l e s s w i t h t h i o g l y c o l l a t e t h a n w i t h i n o r g a n i c d e p r e s s a n t s [ 3 ] , 1.1.4 P r o p e r t i e s of TGA M o l e c u l e T h i o g l y c o l l i c a c i d , a d e r i v a t i v e of c a r b o x y l i c a c i d , c o n t a i n s two r e a c t i v e g r o u p s , a c a r b o x y l group and a mercapto g r o u p . I t has a m e l t i n g p o i n t of -16.5°C, a b o i l i n g p o i n t of 123°C (29 mm Hg) and a d e n s i t y of 1.32, and i s 9 s o l u b l e i n w a t e r , a l c o h o l and e t h e r [ 1 7 ] . The c a r b o n atom of the c a r b o x y l group i s bonded t o t h r e e atoms t h r o u g h a bonds i n w h i c h t h r e e s p 2 - h y b r i d i z e d o r b i t a l s a r e used. The r e m a i n i n g p o r b i t a l o v e r l a p s w i t h the p o r b i t a l of oxygen t o form a it bond. The c a r b o x y l group i s th u s p l a n a r , and bond a n g l e s f o r t h e t h r e e bonds each a p p r o x i m a t e 120°. The hydrogen atom bonded t o oxygen i s e a s i l y i o n i z e d because of t h e o t h e r h i g h l y e l e c t r o n e g a t i v e oxygen; t h e i o n i z e d c a r b o x y l a n i o n i s h i g h l y r e s o n a n c e - s t a b i l i z e d and i n r e a l i t y t h e n e g a t i v e c h a r g e i s d e l o c a l i z e d o v e r t h e t h r e e atom system t h e p a i r of e l e c t r o n s o c c u p y i n g an e x t e n d e d it o r b i t a l w h i c h encompasses b o t h oxygen atoms and t h e i n t e r v e n i n g c a r b o n atom. In t h i s s i t u a t i o n t h e two carbon-oxygen bonds become i d e n t i c a l , as shown by t h e f o l l o w i n g s t r u c t u r e : 0 T h i s h i g h l y e l e c t r o n e g a t i v e COOH group w i t h d r a w s e l e c t r o n s from t h e s u l p h u r o f t h e mercapto g r o u p , t h u s a i d i n g i n t h e i o n i z a t i o n of t h e p r o t o n bonded t o t h e s u l p h u r atom. As a r e s u l t , the c h e m i c a l r e a c t i v i t y of t h e mercapto group i s enhanced. F o r example, t h e i o n i z a t i o n c o n s t a n t f o r HS" a n i o n t o d i s s o c i a t e i n t o H + and S 2" i s 2 x 1 0 " 1 5 [ 8 ] , but the d i s s o c i a t i o n c o n s t a n t f o r SH g r o u p i n TGA i s of t h e o r d e r of 1 0 " 1 1 [ 1 7 ] . TGA i s a l s o e a s i l y o x i d i z e d t o form a dimer t h r o u g h -S-S- b o n d i n g (HOOCCH 2SSCH 2COOH), d i t h i o d i g l y c o l l i c a c i d (DTGA), as shown by t h e h a l f - c e l l r e a c t i o n : 2 TGA = DTGA + 2 H + + 2 e" (1) E° = 0.33 V (vs SHE) [3] The e q u i l i b r i u m d i s s o c i a t i o n c o n s t a n t s a t 25°C a r e 1.2x10-" t o 2.8x10-* f o r t h e c a r b o x y l group and 2.7x10" 1 1 t o 7 . 6 x 1 0 " 1 0 f o r the mercapto group [ 1 7 ] . E i t h e r c a r b o x y l group or mercapto group or bo t h can p a r t i c i p a t e i n c h e m i c a l r e a c t i o n s . 1.1.5 D e p r e s s i v e Mechanism of T h i o g l y c o l l a t e O nly v e r y few p a p e r s have so f a r been p u b l i s h e d r e g a r d i n g the d e p r e s s i v e a c t i o n of t h i o g l y c o l l a t e . N a g a r a j e t a l [7] and Agar [4] b o t h showed t h a t t h i o g l y c o l l a t e was a s t r o n g d e p r e s s a n t f o r c h a l c o p y r i t e and a s t r o n g r e d u c i n g r e a g e n t . Raghavan & Unger [3] have c a r r i e d out a d e t a i l e d s t u d y of t h e i n t e r a c t i o n between t h i o g l y c o l l i c a c i d (TGA) and c h a l c o c i t e . U s i n g a z i n c r e d u c t i o n and i o d i n e t i t r a t i o n t e c h n i q u e , t h e y o b s e r v e d t h e r a p i d p r o d u c t i o n of d i t h i o d i g l y c o l l i c a c i d i n s o l u t i o n upon c o n t a c t w i t h c h a l c o c i t e . They p o s t u l a t e d a mechanism by w h i c h a d s o r b e d TGA r e a c t e d w i t h t h e TGA i n s o l u t i o n t o form an o x i d i z e d d i s u l p h i d e . The r e a c t i o n i s : TGA , + TGA „ = DTGA + 2 e" + 2 H + (2) ads . a q. T h i s r e a c t i o n i s f i r s t o r d e r i n terms of the TGA c o n c e n t r a t i o n i n s o l u t i o n . They b e l i e v e d t h a t t h e c h a l c o c i t e s u r f a c e was c o m p l e t e l y c o v e r e d w i t h a d s o r b e d TGA under t h e t e s t c o n d i t i o n s and t h a t i t c a t a l y s e d t h e o x i d a t i o n . They assumed t h a t t h e amount of a d s o r b e d TGA remained c o n s t a n t , but d i d not d e t e r m i n e how much t h i s amount was nor how i t was a d s o r b e d . I n a d d i t i o n , when c o n s i d e r i n g t h e above p r o p o s e d r e a c t i o n ( 2 ) , i n o r d e r t o m a i n t a i n t h e same amount of TGA on t h e s u r f a c e , one TGA m o l e c u l e s h o u l d be a d s o r b e d o n t o the s u r f a c e i n s t a n t a n e o u s l y upon f o r m a t i o n of a DTGA m o l e c u l e i n t h e s o l u t i o n . T h i s i s d i f f i c u l t t o b e l i e v e . I t may be t h a t t h e s e a u t h o r s p r o p o s e a spontaneous k i n e t i c model i n whi c h o n l y a s i n g l e TGA monolayer i s a d s o r b e d on t h e c h a l c o c i t e s u r f a c e . Whenever a TGA m o l e c u l e comes i n c o n t a c t w i t h t h e s u r f a c e , i t i m m e d i a t e l y r e a c t s w i t h a d j a c e n t TGA i n s o l u t i o n t o form a DTGA m o l e c u l e , w h i c h t h e n comes o f f from t h e s u r f a c e so t h a t a n o t h e r TGA m o l e c u l e can t a k e i t s p l a c e . S i n c e Raghavan and Unger [ 3 ] a l s o o b s e r v e d t h a t DTGA was an e f f e c t i v e d e p r e s s a n t , one may wonder how t h e d e p r e s s i o n c o u l d be a c h i e v e d i f DTGA was so e a s i l y d e s o r b e d from t h e s u r f a c e ? They o f f e r e d no e x p l a n a t i o n f o r t h e d e p r e s s i v e mechanism of DTGA. One p o s s i b i l i t y which might e x p l a i n t h e o b s e r v e d phenomena i s t h a t o n l y TGA i s r e s p o n s i b l e f o r d e p r e s s i o n and when pure DTGA i s added t o s o l u t i o n , an e l e c t r o c h e m i c a l e q u i l i b r i u m i s s e t up so t h a t a s m a l l amount of TGA i s formed. I f t h i s i s t h e c a s e , t h e f o r m a t i o n of DTGA i s a w a s t e f u l c o n s u m p t i o n of TGA and an i n e r t atmosphere t h e n s h o u l d enhance t h e d e p r e s s i v e a c t i o n . 1 .2 O b j e c t i v e of T h i s I n v e s t i g a t i o n I t i s seen from t h e above r e v i e w t h a t t h i o g l y c o l l a t e i s now used p r i m a r i l y i n t h e s e p a r a t i o n of copper-molybdenum s u l p h i d e o r e s , and t h e d e p r e s s i v e mechanisms of t h i o g l y c o l l a t e a r e f a r from c l e a r . I n v i e w of t h i s , t h i s e x p e r i m e n t a l work was u n d e r t a k e n t o : a. T e s t t h e d e p r e s s i v e a c t i o n of t h i o g l y c o l l a t e on s e v e r a l o t h e r s u l p h i d e s and l o o k f o r p o s s i b l e schemes t o s e p a r a t e them. b. Study t h e i n f l u e n c e of oxygen on t h e a d s o r p t i o n of t h i o g l y c o l l a t e and on i t s d e p r e s s i v e a c t i o n . c. E l u c i d a t e , t o some e x t e n t , the mechanisms i n v o l v e d i n t h i o g l y c o l l a t e d e p r e s s i o n of s u l p h i d e m i n e r a l s . CHAPTER 2 EXPERIMENTAL 2.1 M a t e r i a l The m i n e r a l s t e s t e d were c h a l c o p y r i t e , g a l e n a and s p h a l e r i t e . H a n d - s i z e lumps of pure c h a l c o p y r i t e from Timagami, O n t a r i o , and p u r e g a l e n a from O s a v i z a w a , J a p a n , were c r u s h e d and ground i n d i v i d u a l l y . The s i z e f r a c t i o n of -100+150 mesh was used f o r t h e s e e x p e r i m e n t s . P i n e P o i n t s p h a l e r i t e c o n c e n t r a t e , a l s o -100+150 mesh i n s i z e , was a v a i l a b l e i n t h e department of M i n i n g and M i n e r a l P r o c e s s E n g i n e e r i n g (MMPE) a t t h e U n i v e r s i t y of B r i t i s h C o l u m b i a . The s u r f a c e a r e a of each sample was d e t e r m i n e d by n i t r o g e n a d s o r p t i o n u s i n g a Q u a n t a s o r b S o r p t i o n System.* S i n c e t h e s e s u l p h i d e m i n e r a l s a r e r e a d i l y o x i d i z e d when exposed t o t h e atmosphere, t h e y were s u b j e c t t o a p r e t r e a t m e n t p r i o r t o each t e s t t o e s t a b l i s h c l e a n and i d e n t i c a l s u r f a c e s . The p r e t r e a t m e n t was p e r f o r m e d u s i n g an e l u t r i a t o r , v e r y s i m i l a r t o t h e one d e s c r i b e d by H a r r i s and F i n k e l s t e i n [18] (see F i g . 4 ) . For c h a l c o p y r i t e and g a l e n a , * Model QS-2, made by Quantachrome C o r p o r a t i o n , 337 G l e n Cove Road, G r e e v a l e , N.Y., 11548, USA 14 Fig. 4 Schematic diagram of the elutriator used for the pretreatment of sulphide minerals t h i s p r e t r e a t m e n t p r o c e d u r e w a s a s f o l l o w s : a . p l a c e 1 5 g r a m s o f t h e s a m p l e i n t o t h e e l u t r i a t o r . b . w a s h w i t h 1 0 0 0 m l 0 . 1 M d e o x y g e n a t e d h y d r o c h l o r i c a c i d s o l u t i o n . c . s e a l t h e e l u t r i a t o r a n d s e t t o r o t a t e e n d - o v e r - e n d f o r 6 0 m i n u t e s a t a b o u t 3 r p m . d . w a s h w i t h 1 0 0 0 m l d e o x y g e n a t e d d i s t i l l e d w a t e r . T h e s a m p l e w a s t h e n f i l t e r e d , d r i e d a n d s t o r e d i n a v a c u u m d e s i c c a t o r . F o r s p h a l e r i t e c o n c e n t r a t e , a d d i t i o n a l t r e a t m e n t w a s c a r r i e d o u t t o c l e a n t h e s u r f a c e . T h e c l e a n i n g p r o c e d u r e w a s a s f o l l o w s : a . P l a c e 1 5 g r a m s o f s a m p l e i n t o t h e e l u t r i a t o r . b . w a s h w i t h 5 0 0 m l 0 . 1 M d e o x y g e n a t e d s o d i u m s u l p h i d e s o l u t i o n . c . s e a l t h e e l u t r i a t o r a n d s e t t o r o t a t e e n d - o v e r - e n d o v e r n i g h t ( a b o u t 1 5 h o u r s ) a t a b o u t 3 r p m . d . w a s h w i t h 5 0 0 m l 0 . 1 M d e o x y g e n a t e d s o d i u m s u l p h i d e s o l u t i o n a g a i n . e . w a s h w i t h 1 0 0 0 m l d e o x y g e n a t e d d i s t i l l e d w a t e r . f . w a s h w i t h 1 0 0 0 m l 0 . 1 M d e o x y g e n a t e d h y d r o c h l o r i c a c i d s o l u t i o n . g . s e a l t h e e l u t r i a t o r a n d s e t t o r o t a t e f o r 6 0 m i n u t e s a t a b o u t 3 r p m . h . f i n a l l y , w a s h w i t h 1 0 0 0 m l d e o x y g e n a t e d d i s t i l l e d w a t e r . The samples were th e n f i l t e r e d and s t o r e d i n a vacuum d e s i c c a t o r and were t a k e n out j u s t p r i o r t o a t e s t r u n . I t s h o u l d be p o i n t e d out t h a t a l t h o u g h t h e s u l p h i d e m i n e r a l samples have undergone t h e above t r e a t m e n t , t h e y can not be c o n s i d e r e d as c o m p l e t e l y f r e e of o x i d a t i o n p r o d u c t s . T h i s i s because t h e s u r f a c e o x i d a t i o n of t h e s e s u l p h i d e m i n e r a l s happens i n a few seconds when they a r e exposed t o the atmosphere. The m i n e r a l samples t e s t e d i n t h i s e x p e r i m e n t a l work a r e l i s t e d i n T a b l e I I . S y n t h e t i c z i n c s u l p h i d e ( I r t r a n I I m a t e r i a l * from Kodak) was a l s o used f o r some of t h e IR s p e c t r o s c o p i c s t u d i e s . H i g h p u r i t y p o t a s s i u m e t h y l x a n t h a t e , w h i c h was a v a i l a b l e i n t h e Department of MMPE, was used t h r o u g h o u t as a c o l l e c t o r . No i m p u r i t i e s c o u l d be found i n i t s i n f r a r e d s p e c t r u m . F i s h e r b r a n d t h i o g l y c o l l i c a c i d w i t h a s p e c i f i e d p u r i t y o f 96.99% was s u p p l i e d from t h e C h e m i s t r y Department of The U n i v e r s i t y of B r i t i s h C o l u m b i a . Commercial ammonium t h i o g l y c o l l a t e (ATG), w h i c h was produced by Argus C h e m i c a l C o r p o r a t i o n f and c o n t a i n e d 60% NH 4TG, was s u p p l i e d from VW&R.** T e c h n i c a l grade g l y c o l l i c a c i d w i t h a p u r i t y of 65-67%, was bought from BDH C h e m i c a l s . H y d r o c h l o r i c a c i d and sodium h y d r o x i d e were b o t h used as pH m o d i f i e r s . A l l t h e * APPENDIX I shows i t s p r o d u c t i o n and p r o p e r t i e s f 633 C o u r t S t r e e t , B r o o k l y n , N.Y., 11231, USA ** VW&R: Van Waters & Rogers L t d . , 9800 Van Home Way Rmd. Van c o u v e r , B.C., Canada Table II Mineral Samples Mineral Size(mesh) Assay (%) S . S . A V Origin Cu Fe Pb Zn Si0 2 (cm2/g) Chalcopyrite -100+150 25.95 32.0 0.08 0.13 3.34 1223 Timagami.Ont.,Can. Galena -100+150 0.16 0.16 81.0 0.30 1.22 870 Osavizawa.Japan Galena ** -150 0.16 0.16 81.0 0.30 1.22 1132 Osavizawa,Japan Sphalerite -100+150 0.02 1.5 0.40 64.5 0.12 2183 Pine Poj.nt,NWT,Can. * Specific surface area, determined by nitrogen adsorption. ** Deslimed by elutriation. o t h e r r e a g e n t s used were of a n a l y t i c a l g r a d e . 2.2 M i c r o f l o t a t i o n 2.2.1 H a l l i m o n d Tube F l o t a t i o n The f l o a t a b i l i t i e s of t h e s i n g l e m i n e r a l samples, m o d i f i e d by the r e a g e n t s , were t e s t e d i n a H a l l i m o n d Tube [ 1 9 ] . Two grams of sample were c o n d i t i o n e d w i t h 100 ml p o t a s s i u m e t h y l x a n t h a t e s o l u t i o n f o r a p e r i o d of 5 m i n u t e s , t h e n a c e r t a i n amount of t h e d e p r e s s a n t was added. The pH of the p u l p was a d j u s t e d , and c o n d i t i o n i n g was c o n t i n u e d f o r a f u r t h e r 5 m i n u t e s . The p u l p was then t r a n s f e r r e d t o the H a l l i m o n d Tube. W h i l e b e i n g kept w e l l - s u s p e n d e d by a m a g n e t i c s t i r r i n g b a r , t h e p u l p was f l o a t e d i n a n i t r o g e n f l o w o f 30 ml/minute f o r 1 m i n u t e . I n some of t h e t e s t s , the c o n d i t i o n i n g p r o c e d u r e was r e v e r s e d p u r p o s e l y . The s p h a l e r i t e sample was a c t i v a t e d by copper p r i o r t o c o n d i t i o n i n g w i t h x a n t h a t e . T h i s was a c h i e v e d by r e a c t i n g 16 grams of s p h a l e r i t e w i t h 400 ml 4 X 1 0 " *M copper s u l p h a t e s o l u t i o n f o r 15 m i n u t e s a t i t s n a t u r a l pH. By m e a s u r i n g the r e s i d u a l copper c o n c e n t r a t i o n , t h e copper c o v e r a g e on s p h a l e r i t e was found t o be 0.4 monolayer a t t h i s c o n d i t i o n . The c a l c u l a t i o n was c a r r i e d out on t h e a s s u m p t i o n t h a t each copper atom o c c u p i e d 1.04x10" 1 9 m2 of the s u r f a c e s i t e . 2.2.2 P/S C e l l F l o t a t i o n * S y n t h e t i c m i n e r a l m i x t u r e s were s e p a r a t e d w i t h a 100 ml P/S c e l l . A f t e r a c o n d i t i o n i n g p e r i o d as d e s c r i b e d i n the p r e v i o u s s e c t i o n , t h e m i x t u r e was t r a n s f e r r e d t o t h e P/S c e l l . The f l o t a t i o n s e p a r a t i o n was c o n d u c t e d a t a n i t r o g e n f l o w of 30 m l / m i n u t e , w h i l e t h e amount of sample and f l o t a t i o n t i m e were s p e c i f i e d i n d i v i d u a l l y . The amount of each m i n e r a l i n t h e p r o d u c t ( c o n c e n t r a t e and t a i l ) was a s s a y e d by a t o m i c a b s o r p t i o n s p e c t r o s c o p y i n t h e a s s a y l a b o r a t o r y of t h e Dept. of MMPE. T h i s P/S c e l l was a l s o u t i l i z e d f o r s i n g l e m i n e r a l f l o t a t i o n w i t h p o t e n t i a l measurements (see F i g . 5a and 5b f o r t h e m o d i f i e d c e l l ) . Four e l e c t r o d e s were used: a p l a t i n u m e l e c t r o d e c o u p l e d w i t h a s a t u r a t e d c a l o m e l e l e c t r o d e t o measure t h e s o l u t i o n redox p o t e n t i a l , an oxygen e l e c t r o d e t o measure t h e oxygen c o n c e n t r a t i o n i n t h e s o l u t i o n and a combined e l e c t r o d e t o m o n i t o r t h e pH v a l u e of t h e s o l u t i o n . The o u t p u t s of t h e e l e c t r o d e s were r e c o r d e d s i m u l t a n e o u s l y . Redox p o t e n t i a l of t h e s o l u t i o n was r e c o r d e d w i t h a Beckman 10 i n c h r e c o r d e r . The r e a d i n g s were ch e c k e d by a c o n s t a n t power s o u r c e and a K e i t h l e y m u l t i m e t e r . f The e l e c t r o d e s were c a l i b r a t e d a g a i n s t s t a n d a r d s o l u t i o n s [ 2 1 ] , Oxygen c o n c e n t r a t i o n was measured by YSI Model 54 oxygen * P a r t r i d g e / S m i t h f l o t a t i o n c e l l , see r e f e r e n c e [ 2 0 ] . t Model 171, made by K e i t h l e y I n s t r u m e n t s I n c . , 28775 A u r o r a Road, C l e v e l a n d , O h i o , 44139 USA F i g . 5a Schematic Diagram of the P/S C e l l Equipped with Four Electrodes f o r the Simultaneous Measurements of pH, Oxygen Concentration and Redox P o t e n t i a l of the F l o t a t i o n Pulp. F i g . 5b The Modified P/S C e l l at Work. N3 O meter, and r e c o r d e d by a n o t h e r Beckman 10 i n c h r e c o r d e r . The pH v a l u e of the s o l u t i o n was measured and r e c o r d e d by an E l e c t r o s c a n 30 p o t e n t i o m e t e r . These m i c r o - f l o t a t i o n t e s t s w i t h p o t e n t i a l measurement were c o n d u c t e d i n b o t h a e r a t e d and a r g o n - s a t u r a t e d s o l u t i o n s . a. I n a e r a t e d s o l u t i o n . Two grams of x a n t h a t e d sample were p l a c e d i n t o t h e P/S c e l l , 100 ml of 0.001M d e p r e s s a n t s o l u t i o n were added and t h e pH was a d j u s t e d . The m i x t u r e was c o n d i t i o n e d f o r 10 m i n u t e s . M e d i c a l a i r ( b r e a t h i n g grade) was a l l o w e d t o f l o w t h r o u g h t h e c e l l from a h o l e i n the m i d d l e of t h e c e l l d u r i n g t h i s c o n d i t i o n i n g p e r i o d t o m a i n t a i n t h e oxygen c o n c e n t r a t i o n i n s o l u t i o n a t a s a t u r a t i o n v a l u e of 8.2 ppm. A f t e r c o n d i t i o n i n g , t h e sample was f l o a t e d i n an a i r f l o w of 30 ml/minute f o r 2 m i n u t e s . The samples were x a n t h a t e d i n s o l u t i o n s s a t u r a t e d w i t h m e d i c a l a i r . b. I n a r g o n - s a t u r a t e d s o l u t i o n . The 0.001M d e p r e s s a n t s o l u t i o n was p u r g e d w i t h p ure argon i n a 2000 ml f l a s k f o r 30 m i n u t e s p r i o r t o u se. The argon was p r e v i o u s l y p a s s e d t h r o u g h a b o t t l e of a l k a l i n e p y r o g a l l o l s o l u t i o n i n o r d e r t o remove t r a c e s of oxygen. A two gram x a n t h a t e d sample was p l a c e d i n t o the c e l l , t h e n argon was a l l o w e d t o f l o w t h r o u g h t h e c e l l u n t i l t h e oxygen meter i n d i c a t e d a z e r o r e a d i n g . Then 100 ml of the deox y g e n a t e d d e p r e s s a n t s o l u t i o n was i n t r o d u c e d and th e pH was a d j u s t e d . The m i x t u r e was c o n d i t i o n e d f o r 10 m i n u t e s . Argon was purged t h r o u g h t h e c e l l d u r i n g c o n d i t i o n i n g t o m a i n t a i n an oxygen c o n c e n t r a t i o n of l e s s than 0.001 ppm, as i n d i c a t e d by t h e YSI model 54 oxygen meter. A f t e r c o n d i t i o n i n g , t h e m a t e r i a l was f l o a t e d w i t h 30 ml/minute argon f o r 2 m i n u t e s . I n t h i s s e r i e s of t e s t s , t h e samples were p r e v i o u s l y x a n t h a t e d i n a r g o n - s a t u r a t e d s o l u t i o n s . F o r c o m p a r i s o n p u r p o s e , t e s t s were a l s o c o n d u c t e d u s i n g samples x a n t h a t e d i n s o l u t i o n s s a t u r a t e d w i t h m e d i c a l a i r . 2.3 D e t e r m i n a t i o n of A d s o r p t i o n and D e s o r p t i o n 2.3.1 T h i o g l y c o l l i c A c i d (TGA) The c o n c e n t r a t i o n of t h i o g l y c o l l i c a c i d was d e t e r m i n e d by i o d i n e t i t r a t i o n [3] [ 2 2 ] , I t i s b e l i e v e d t h a t TGA i s o x i d i z e d t o i t s c o r r e s p o n d i n g dimer (DTGA) d u r i n g t i t r a t i o n [ 2 2 ] . The r e a c t i o n i s : 2 HSCH 2COOH + I 2 = HOOCCH 2SSCH 2COOH + 2 HI (3) T h i s i n d i c a t e s t h a t o n l y t h e c o n c e n t r a t i o n of the monomer can be d e t e r m i n e d by t i t r a t i o n . To d e t e r m i n e the c o n c e n t r a t i o n of TGA s o l u t i o n c o n t a i n i n g d i m e r , t h e s o l u t i o n was f i r s t r e d u c e d by z i n c m e t a l then t i t r a t e d w i t h i o d i n e [ 2 3 ] , The c o n d i t i o n s i n w h i c h t h i s t i t r a t i o n c o u l d be p e r f o r m e d were d e t e r m i n e d and a r e d e s c r i b e d i n APPENDIX I I . 2.3.2 E t h y l X a n t h a t e The c o n c e n t r a t i o n of e t h y l x a n t h a t e was d e t e r m i n e d by u l t r a v i o l e t s p e c t r o s c o p y . Measurements were made a t the s t r o n g x a n t h a t e a b s o r p t i o n peak of 301 nm u s i n g a P e r k i n - E l m e r Model Lambda 3 UV-VIS s p e c t r o p h o t o m e t e r . A s t a n d a r d c a l i b r a t i o n c u r v e was e s t a b l i s h e d by m e a s u r i n g th e a b s o r b a n c e of a s e r i e s of e t h y l x a n t h a t e s o l u t i o n s a t t h e i r n a t u r a l pH v a l u e s . T h i s c u r v e i s shown i n F i g . 6. 2.3.3 T e s t P r o c e d u r e The a d s o r p t i o n of TGA o n t o t h e m i n e r a l s u r f a c e , and t h e r e m o v a l of e t h y l x a n t h a t e from th e m i n e r a l s u r f a c e were d e t e r m i n e d s i m u l t a n e o u s l y . A t y p i c a l t e s t f l o w s h e e t i s shown i n F i g . 7 . When a d s o r p t i o n and d e s o r p t i o n were t o be c o n d u c t e d i n an i n e r t a t m o s p h e r e , the s t i r r i n g was p e r f o r m e d i n a s e a l e d b e aker p u r g e d w i t h n i t r o g e n . The s o l u t i o n was p r e v i o u s l y p u r g e d w i t h n i t r o g e n f o r 30 m i n u t e s b e f o r e t h e sample was i n t r o d u c e d . 0 -1.4 I I -6 -5 -4 log C F i g . 6 Beer's Law for Potassium Et h y l Xanthate Using a 1 cm Quartz C e l l ( at 301 nm ) Xanthated sample 50 ml 10 3M TGA, adjust pH S t i r F i l t r a t i o n 20 ml f i l t r a t e , t i t r a t e d i r e c t l y with 0.005N I„ 20 ml f i l t r a t e , adjust pH to 1, add zinc metal, s t i r 5 min. A few ml of f i l t r a t e , f o r UV spectrophoto-metry F i l t r a t i o n Readjust pH to 3.5 - 7, t i t r a t e with 0.005N I„ F i g . 7 Adsorption/Desorption Test Procedure 2.4 Zeta P o t e n t i a l Measurements To measure the s u r f a c e c h a rge of m i n e r a l t r e a t e d w i t h r e a g e n t s , 0.5 gram sample was ground i n an agate m o r t a r f o r two or t h r e e m i n u tes then p l a c e d i n 50 ml reagent s o l u t i o n . A f t e r s t i r r i n g 5 m i n u t e s a t t h e r e q u i r e d pH v a l u e , t h e s u p e r n a t a n t was poured i n t o an e l e c t r o p h o r e s i s c e l l ( t h u s o n l y the f i n e p a r t i c l e s w h i c h were suspended i n s u p e r n a t a n t went t o t h e c e l l ) t o measure the e l e c t r o p h o r e t i c m o b i l i t y of t h e c o l l o i d a l m i n e r a l p a r t i c l e s . F or each sample, t e n p a r t i c l e s were t r a c k e d a l o n g one m i c r o d i v i s i o n , and t h e a v e r a g e m i c r o e l e c t r o p h o r e t i c m o b i l i t y was c a l c u l a t e d . 2. 5 I d e n t i f i c a t i o n of R e a c t i o n P r o d u c t s A P e r k i n - E l m e r Model 283B d o u b l e beam i n f r a r e d s p e c t r o p h o t o m e t e r was used t o i d e n t i f y the s u r f a c e r e a c t i o n p r o d u c t s . S p e c t r a were r e c o r d e d u s i n g b o t h t r a n s m i t t a n c e and r e f l e c t a n c e t e c h n i q u e s . 2.5.1 T r a n s m i s s i o n S p e c t r a The c o n v e n t i o n a l KBr p e l l e t method was employed [ 2 4 ] . Samples of c h a l c o p y r i t e , g a l e n a and s y n t h e t i c z i n c s u l p h i d e were f i r s t ground i n a Spex t u n g s t e n c a r b i d e m i l l * f o r one t o two h o u r s . Each sample was t h e n p l a c e d i n a 1000 ml c y l i n d e r and a l l o w e d t o s e t t l e f o r a p e r i o d of time a f t e r * Model 8000-11, made by Spex I n d u s t r i e s I n c . 3880 Park Ave., Metuchen, N.J., USA which t h e p a r t i c l e s r e m a i n i n g i n the s u p e r n a t a n t were a l l c a l c u l a t e d t o be l e s s than 2.5 m i c r o n s . No r e a g e n t s e x c e p t pH m o d i f i e r s were added d u r i n g t h e s e d i m e n t a t i o n of t h e m i n e r a l s a m p l e s . The s u p e r n a t a n t was then f i l t e r e d . The cake was d r i e d and s t o r e d i n a vacuum d e s i c c a t o r f o r use i n p r e p a r i n g KBr p e l l e t s . To make a KBr p e l l e t , 100 mg of the above sample was r e a c t e d w i t h 50 ml 0.01M r e a g e n t s o l u t i o n . For g a l e n a , the c o n c e n t r a t i o n of s o l u t i o n was sometimes 0.001M, whi c h was s p e c i f i e d i n d i v i d u a l l y . A f t e r f i l t e r i n g and d r y i n g the sample, a g i v e n amount was weighed out (0.5 mg f o r c h a l c o p y r i t e and g a l e n a , 1 mg f o r z i n c s u l p h i d e ) , mixed w i t h 300 mg KBr i n an a g a t e m o r t a r . A f t e r 3 m i nutes of subsequent vacuum e v a c u a t i o n i n t h e d i e , t h e m i x t u r e was p r e s s e d i n t o a t r a n s p a r e n t p e l l e t a t 4800 p s i and then s u b j e c t e d t o IR i d e n t i f i c a t i o n . The r e s t of the d r y sample was then r e a c t e d w i t h t h e second r e a g e n t , and t h e above p r o c e d u r e r e p e a t e d . 2.5.2 A t t e n u a t e d T o t a l R e f l e c t a n c e S p e c t r a When a beam of r a d i a t i o n e n c o u n t e r s an i n t e r f a c e between two o p t i c a l l y d i s t i n c t m edia, a p o r t i o n of i t e n t e r s t h e second medium and a p o r t i o n i s r e f l e c t e d from t h e s u r f a c e . I f t h e r a d i a t i o n a p p r o a c h e s t h e i n t e r f a c e from the d i r e c t i o n of the medium of g r e a t e r r e f r a c t i v e i n d e x and t h e a n g l e of i n c i d e n c e exceeds t h e c r i t i c a l a n g l e f o r t o t a l i n t e r n a l r e f l e c t i o n , the r a d i a t i o n can be t o t a l l y r e f l e c t e d . I n t h i s s i t u a t i o n an e v a n e s c e n t wave i s p r o p a g a t e d a l o n g t h e d i r e c t i o n of the i n t e r f a c e . I t s e x t e n s i o n i n t o the o p t i c a l l y r a r e r medium i s damped e x p o n e n t i a l l y and v e r y r a p i d l y , but the wave i s exposed t o t h e medium e f f e c t i v e l y enough t o be a t t e n u a t e d a c c o r d i n g t o t h e a b s o r p t i o n c o e f f i c i e n t of t h a t medium. I f a sample of some m a t e r i a l i s i n t i m a t e l y j o i n e d t o the s u r f a c e of an o p t i c a l l y d e n s e r m a t e r i a l , r a d i a t i o n t h a t would o t h e r w i s e be t o t a l l y i n t e r n a l l y r e f l e c t e d a t the s u r f a c e i s a t t e n u a t e d by t h e sample.. T h i s i s what i s c a l l e d the a t t e n u a t e d t o t a l r e f l e c t i o n (ATR). In t h i s e x p e r i m e n t a l work a H a r r i c k v e r s a t i l e r e f l e c t i o n a t t a c h m e n t was p l a c e d i n the sample chamber of the i n f r a r e d s p e c t r o p h o t o m e t e r and a z i n c s u l p h i d e p r i s m was used as a do u b l e s a m p l i n g i n t e r n a l r e f l e c t i o n element (see F i g . 8 f o r the o p t i c a l s y s t e m ) . At an i n c i d e n t a n g l e of 45°, t h i s p r i s m p roduces 63 i n t e r n a l r e f l e c t i o n s . I n t h i s way, the a b s o r p t i o n by a t h i n f i l m of sample on t h e p r i s m s u r f a c e can be i n t e n s i f i e d . The s p e c t r a p r e s e n t e d a r e t h e d i f f e r e n c e between the s p e c t r a a f t e r and t h e s p e c t r a b e f o r e r e a g e n t t r e a t m e n t of t h e p r i s m . F o r r e p e a t e d use, the p r i s m was c l e a n e d i n a plasma c l e a n e r * a t s e t t i n g 9 f o r 4 m i n u t e s . f * Made by H a r r i c k S c i e n t i f i c C o r p o r a t i o n , C r o t o n Dam Road, Box 867, O s s i n i n g , N.Y. 10562, USA t I n f r a r e d s p e c t r a i n d i c a t e d t h a t no o r g a n i c s were p r e s e n t a t t h e ZnS p r i s m s u r f a c e a f t e r t r e a t m e n t i n t h e c l e a n e r a t t h i s c o n d i t i o n . 29 Fig. 8 Optical Path of the Multiple Internal Reflection Attachment. CHAPTER 3 EXPERIMENTAL RESULTS 3.1 Predominant S p e c i e s i n TGA S o l u t i o n I t has been mentioned t h a t t h i o g l y c o l l i c a c i d has t h e f o r m u l a : HS-CH 2-COOH. Bot h the c a r b o x y l and t h e mercapto groups p o s s e s s a c i d i c p r o p e r t i e s . From the a c i d - b a s e t i t r a t i o n c u r v e of t h e TGA used i n t h e s e e x p e r i m e n t s ( F i g . 9 ) , i t was o b s e r v e d t h a t TGA underwent o n l y one s t e p d i s s o c i a t i o n i n the pH range t e s t e d . The d i s s o c i a t i o n c o n s t a n t was c a l c u l a t e d t o be 2.5x10"", u s i n g a method d e s c r i b e d i n r e f e r e n c e [ 2 5 ] , T h i s s u g g e s t s t h a t o n l y d i s s o c i a t i o n of t h e c a r b o x y l group o c c u r s : HSCH2COOH = HSCH 2C00- + H + (4) K = 2.5x10-" I t i s known t h a t t h i o g l y c o l l i c a c i d can be o x i d i z e d t o i t s c o r r e s p o n d i n g d i m e r . I t has been r e p o r t e d t h a t d i l u t e d TGA s o l u t i o n was o x i d i z e d r a p i d l y when s t o r e d i n a c l e a r f l a s k [ 3 ] . T e s t r e s u l t s showed t h a t as l o n g as t h e f l a s k was w e l l s t o p p e r e d , t h e TGA would not be o x i d i z e d f o r a f a i r l y 10 15 20 Volume of NaOH, ml 25 30 F i g . 9 T i t r a t i o n Curve of T h i o g l y c o l l i c Acid (TGA) TGA: 0.01 M, 100 ml NaOH: 0.102 M l o n g p e r i o d of t i m e (see F i g . 10). In b o t h i o d i n e and a c i d - b a s e t i t r a t i o n s , t h e amount of i o d i n e and NaOH consumed was v e r y c l o s e t o t h e e q u i v a l e n t amount. T h i s meant t h a t t h e c o n c e n t r a t i o n of TGA d e t e r m i n e d by a c i d - b a s e t i t r a t i o n was e q u a l t o t h a t d e t e r m i n e d by i o d i n e t i t r a t i o n , w h i c h i n d i c a t e d t h a t t h e TGA was r e l a t i v e l y pure and f r e e of e a s i l y o x i d i z e d i m p u r i t i e s . The above r e s u l t s s u g g e s t e d t h a t t h e predominant s p e c i e s i n a s t o c k e d TGA s o l u t i o n were pure TGA and i t s d i s s o c i a t i o n p r o d u c t t h i o g l y c o l l a t e . As shown i n F i g . 11, above pH 6, TGA was c o m p l e t e l y d i s s o c i a t e d . 3.2 S t o i c h i o m e t r y of T h i o g l y c o l l a t e S a l t F o r m a t i o n TGA r e a c t s w i t h copper s u l p h a t e t o form a b l a c k p r e c i p i t a t e and w i t h l e a d n i t r a t e t o form a l i g h t y e l l o w p r e c i p i t a t e . I n p r i n c i p l e , t h e s e m e t a l i o n s c o u l d be a t t a c h e d t o e i t h e r t h e c a r b o x y l group, or t h e mercapto group, or t o b o t h . To d e t e r m i n e t o w h i c h group th e m e t a l i o n s have been a t t a c h e d , a s t o i c h i o m e t r i c r e a c t i o n t e s t was c o n d u c t e d . Because of t h e d i f f i c u l t i e s i n d e t e r m i n i n g t h e c o n c e n t r a t i o n of TGA i n the m u l t i s p e c i e s system ( i o d i n e t i t r a t i o n t e c h n i q u e was used, w h i c h i s an o x i d a t i o n - r e d u c t i o n p r o c e s s ) , a l a r g e dosage of m e t a l i o n s was used a g a i n s t TGA. T e s t s were c o n d u c t e d a t a low pH ( a p p r o x i m a t e l y 3) and a t a h i g h pH (7-9) f o r b o t h copper and £r — & _ equivalent. yolume_ O 0 5 10 15 20 25 30 Time of Storage, day F i g . 10 Iodine T i t r a t i o n of Stocked T h i o g l y c o l l i c Acid Solution _2 0.005 N I 2 / l ml 10 M stocked s o l u t i o n O TGA solutions stored i n well-stopped clear f l a s k ; A TGA so l u t i o n s stored in a beaker open to a i r . 2 3 4 5 6 7 8 9 10 11 12 13 P H F i g . 11 D i s s o c i a t i o n of T h i o g l y c o l l i c Acid D i s s o c i a t i o n constant: 2.51 x 10 [R ]: concentration of t h i o g l y c o l l a t e group, H S C R ^ C O O " CQ: o r i g i n a l concentration of t h i o -g l y c o l l i c a c i d l e a d . The r e s u l t s a r e l i s t e d i n T a b l e I I I . As s e e n , a t pH of a p p r o x i m a t e l y 3, a l a r g e amount of r e s i d u a l m e t a l i o n s was p r e s e n t i n t h e system, t h u s i t c o u l d be assumed t h a t t h e TGA had been t o t a l l y consumed. The s t o i c h i o m e t r i c r a t i o s were v e r y c l o s e t o 1 a t pH 3 f o r b o t h m e t a l i o n s . As shown by t h e P o u r b a i x diagrams [26] (see Appendix I I I ) , under t h i s c o n d i t i o n , the m e t a l s were p r e s e n t i n t h e system as pure m e t a l i o n s , i t was t h u s c o n s i d e r e d t h a t no o t h e r r e a c t i o n s than m e t a l - t h i o g l y c o l l a t e p r e c i p i t a t i o n c o u l d o c c u r . T h i s i n d i c a t e s t h a t a t t h i s low pH, one m e t a l i o n r e a c t s w i t h one TGA m o l e c u l e t o form a p r i c i p i t a t e . H i g h e r consumption of m e t a l i o n s a t h i g h pH v a l u e s was p r o b a b l y due t o the f o r m a t i o n of h y d r o x i d e as w e l l a s t h i o g l y c o l l a t e ( a l s o see Appendix I I I f o r t h e P o u r b a i x d i a g r a m s ) . 3.3 D e p r e s s i v e A c t i o n of TGA on S u l p h i d e M i n e r a l s H a l l i m o n d Tube f l o t a t i o n r e s u l t s f o r c h a l c o p y r i t e , g a l e n a and c o p p e r - a c t i v a t e d s p h a l e r i t e , u s i n g TGA as d e p r e s s a n t , a r e p r e s e n t e d i n F i g s . 12 t o 14. The d e p r e s s i v e a c t i o n was marked on a l l t h e s u l p h i d e m i n e r a l s t e s t e d . The g e n e r a l o b s e r v a t i o n was t h a t f o r a g i v e n c o n c e n t r a t i o n o f TGA, t h e r e was a narrow pH range i n w h i c h t h e s u l p h i d e m i n e r a l s became n o n f l o a t a b l e . They then remained u n f l o a t e d w i t h an i n c r e a s e i n pH. These c r i t i c a l pH v a l u e s f o r 1 0 _ , M TGA were, f o r example, about 9 f o r c h a l c o p y r i t e , 8 f o r Table I I I Stoichiometry of the Reaction Between TGA and Copper or Lead Ions O r i g i n a l TGA* 1.009x10"3 Metal ion C u " P b " O r i g i n a l metal* 2.124xl0~ 3 2.008xl0~ 3 pH 3.06 8.94 3.10 7.48 F i n a l metal 9.442xl0~ 4 3.148xl0~ 6 1.042x10~3 3.668xl0" 4 Reacted metal 1.18xl0~ 3 2.12xl0" 3 9.66x10"4 1.64xl0 - 3 Reacted/ metal /TGA 1.17 2.10 0.96 1.63 Solution redox p o t e n t i a l , mv** +443 +348 +242 +226 * Units for the mater i a l s are "moles". ** vs. S.H.E 37 pH Fig.12 Hallimond Tube F l o t a t i o n of Chalcopyrite Treated with Potassium E t h y l Xanthate and T h i o g l y c o l l i c Acid chalcopyrite/10~ 4M KEX: 2g/100ml O no TGA; • 10 _ 5M TGA; O 10~ 4M TGA; A 10~ 3M TGA 13 Hallimond Tube F l o t a t i o n of Galena Treated with Potassium Ethyl Xanthate (KEX) and T h i o g l y c o l l i c Acid (TGA) Galena/10~ 4M KEX: '2g/100ml O no TGA; • 10~5M TGA; O 10 M TGA; A 10~ M TGA 2 3 4 5 6 7 8 9 10 11 12 13 PH F i g . 14 Hallimond Tube F l o t a t i o n of Cu-activated Sphalerite Treated with Potassium Ethyl Xanthate(KEX) and T h i o g l y c o l l i c Acid(TGA) -4 Sphalerite/10 M KEX: 2g/100ml O no TGA; • 10~5M TGA; O 10 M TGA; A 10 M TGA C u - a c t i v a t e d s p h a l e r i t e and 4 f o r g a l e n a . The most marked d e p r e s s i o n by TGA was o b s e r v e d w i t h g a l e n a . R e v e r s i n g t h e o r d e r of r e a g e n t a d d i t i o n from KEX + TGA t o TGA + KEX d i d not seem t o change the d e p r e s s i v e a c t i o n . F i g s . 15 and 16 show t h e t e s t r e s u l t s w i t h c h a l c o p y r i t e and g a l e n a . B o t h i n d i c a t e t h e same d e p r e s s i o n of m i n e r a l s . Ammonium t h i o g l y c o l l a t e , which has been used i n c o m m e r c i a l f l o t a t i o n s e p a r a t i o n s , a l s o e f f e c t i v e l y d e p r e s s e d c h a l c o p y r i t e (see F i g . 17). A c o m p a r i s o n was made between t h i o g l y c o l l i c a c i d and g l y c o l l i c a c i d (GA). As shown i n F i g s . 18 and 19* , w h i l e TGA showed a marked d e p r e s s i v e a c t i o n , GA had no d e p r e s s i v e a c t i o n a t a l l . 3.4 A d s o r p t i o n of TGA and Removal of A d s o r b e d X a n t h a t e I n t h i s s e r i e s of t e s t s , the x a n t h a t e d sample was c o n d i t i o n e d w i t h TGA s o l u t i o n f o r 5 m i n u t e s , t h e n t h e c o n c e n t r a t i o n s of TGA and e t h y l x a n t h a t e were d e t e r m i n e d and the c o r r e s p o n d i n g a d s o r p t i o n and d e s o r p t i o n c a l c u l a t e d . DTGA was not d e t e c t e d w i t h i o d i n e t i t r a t i o n i n t h i s s h o r t p e r i o d of c o n d i t i o n i n g , i t s c o n c e n t r a t i o n was thus t a k e n as z e r o . The r e s u l t s f o r c h a l c o p y r i t e , C u - a c t i v a t e d s p h a l e r i t e and g a l e n a a r e shown i n F i g s . 20, 21 and 22, r e s p e c t i v e l y . * T e s t s w i t h unwashed samples. C h a l c o p y r i t e i s -150+200 mesh. 41 F i g . 1 5 Depression E f f e c t of T h i o g l y c o l l i c Acid on Chalcopyrite -4 -4 Chalcopyrite/10 M KEX, 10 M TGA: 2g/100ml F l o t a t i o n : Hallimond Tube A Conditioned with KEX, then with TGA O Conditioned with TGA, then with KEX 100 90 80 70 60 43 CD u 50 40 Fig.16 Depression E f f e c t of T h i o g l y c o l l i c Acid on Galena -4 -4 Galena/10 M KEX, 10 M TGA: 2g/100ml F l o t a t i o n : Hallimond Tube A Conditioned with KEX, then with TGA O Conditioned with TGA, then with KEX 2 3 4 5 6 7 8 9 10 11 12 13 pH 18 Depressive action of g l y c o l l i c acid (GA) and t h i o -g l y c o l l i c acid (TGA) on chalcopyrite. -4 chalcopyrite/10 M KEX: 2g/100ml A 10~3M GA O 10~3M TGA 7 pH 10 11 12 13 19 Depressive a c t i o n of g l y c o l l i c a c i d (GA) and t h i o -g l y c o l l i c a c i d (TGA) on galena. -4 galena/10 M KEX: 2g/100ml o 10 4M GA 10~4M TGA 46 o CO < u cfl u c o 1-4 cu 100 90 -80 -70 -60 -50 _ 40 _ 30 " 20 -10 -0 10 ,11 12 13 2 3 4 5 6 7 8 9 PH Fig. 20 Adsorption of Thioglycollic Acid on Chalcopyrite and Corresponding Removal of Adsorbed Potassium Ethyl Xanthate _3 Chalcopyrite/10 M TGA: lg/50ml D KEX remaining on surface (no TGA) _3 O KEX remaining on Surface (10 M TGA) A TGA adsorbed 0) J3 U O CO < CD 00 CO 4-1 c 0) o u cu 100 90 -80 -70 -60 -50 . 40 -30 . 20 " 10 -0 10 11 12 13 2 3 4 5 6 7 8 « pH F i g . 21 Adsorption of T h i o g l y c o l l i c Acid on Cu-activated s p h a l e r i t e and Corresponding Removal of Adsorbed Potassium E t h y l Xanthate Sphalerite/10 3M TGA 0.5g/50ml • O A KEX remaining on surface (no TGA) -3 KEX remaining on surface (10 M TGA) TGA adsorbed on surface 2 3 4 5 6 7 8 9 10 11 12 13 pH Fig.22 Adsorption of T h i o g l y c o l l i c Acid on Galena and Corresponding Removal of Adsorbed Potassium E t h y l Xanthate Galena/10~ 3M TGA: 0.8g/50ml • KEX remaining on surface( no TGA) O KEX remaining on surface(10 M TGA) A TGA adsorbed I t seemed t h a t a d s o r p t i o n of TGA on b o t h c h a l c o p y r i t e and C u - a c t i v a t e d s p h a l e r i t e had a maximum a t around n e u t r a l pH; a d s o r p t i o n d e c r e a s e d a t b o t h h i g h e r and lower pH. The a d s o r p t i o n on g a l e n a seemed t o be c o n s t a n t a t a c i d i c and n e u t r a l pH, and f e l l o f f i n a l k a l i n e s o l u t i o n s . In f a c t , t h e s e d i f f e r e n c e s may not be s i g n i f i c a n t . A s t r a i g h t , h o r i z o n t a l l i n e c o u l d be drawn t h r o u g h the d a t a p o i n t s . B e s i d e s , the a d s o r p t i o n was d e t e r m i n e d by m e a s u r i n g the r e s i d u a l c o n c e n t r a t i o n of TGA, w h i c h , i n t u r n , was d e t e r m i n e d by i o d i n e t i t r a t i o n . I n t h e i o d i n e t i t r a t i o n , t h e i o d i n e consumed can be more than a c t u a l l y needed a t b o t h low and h i g h pH v a l u e s (APPENDIX I I ) . I t i s t h u s easy t o see t h a t a t t h e s e low o r h i g h pH v a l u e s , a h i g h e r r e s i d u a l c o n c e n t r a t i o n of TGA might be o b t a i n e d l e a d i n g t h e r e f o r e t o a l o w e r a d s o r p t i o n . Assuming t h a t each t h i o g l y c o l l a t e r a d i c a l o c c u p i e d 2 x 1 0 " 1 9 m 2 o f s u r f a c e s i t e , t h e c o v e r a g e of TGA on t h e m i n e r a l s u r f a c e s a t n e u t r a l pH v a l u e s would be 12 mo n o l a y e r s f o r c h a l c o p y r i t e , 15 m o n o l a y e r s f o r C u - a c t i v a t e d s p h a l e r i t e and 6 m o n o l a y e r s f o r g a l e n a . The c r o s s s e c t i o n a l a r e a of 2 x 1 0 " 1 9 m2 was chosen f o r the c a r b o x y l group based on s i m i l a r s t r u c t u r e s . I t was e x p e c t e d t h a t t h e c r o s s s e c t i o n a l a r e a of mercapto group was l e s s t h a n t h i s v a l u e . Thus, even i f t h e TGA m o l e c u l e s a d s o r b e d on t h e s u r f a c e took d i f f e r e n t o r i e n t a t i o n s , t h e s u r f a c e a r e a o c c u p i e d by a s i n g l e TGA m o l e c u l e w o u l d not exceed 6 x 1 0 " 1 9 m 2. At t h i s maximum v a l u e , the m u l t i l a y e r c o v e r a g e on t h e m i n e r a l s u r f a c e was s t i l l v a l i d . Removal of p r e v i o u s l y a d s o r b e d e t h y l x a n t h a t e was s i g n i f i c a n t i n t h e p r e s e n c e of TGA, e s p e c i a l l y a t h i g h pH v a l u e s . A g a i n , the most marked removal of x a n t h a t e was o b s e r v e d w i t h g a l e n a : a t a pH v a l u e of around 11 p r e v i o u s l y a d s o r b e d e t h y l x a n t h a t e was c o m p l e t e l y removed; but w i t h o u t TGA, o n l y 30% was removed a t t h i s pH v a l u e . 3.5 E f f e c t of Oxygen on t h e A d s o r p t i o n of TGA A d s o r p t i o n t e s t s were c o n d u c t e d w i t h e x t e n d e d c o n d i t i o n i n g . M i n e r a l samples were c o n d i t i o n e d i n TGA s o l u t i o n a t i t s n a t u r a l pH (3.4) f o r up t o 4 h o u r s i n b o t h a e r a t e d s o l u t i o n s and n i t r o g e n - s a t u r a t e d s o l u t i o n s . The t e s t r e s u l t s f o r c h a l c o p y i t e , C u - a c t i v a t e d s p h a l e r i t e and g a l e n a a r e shown from F i g . 23 t o F i g . 28. DTGA was d e t e c t e d f o r a l l t h r e e m i n e r a l s a t b o t h a e r a t e d c o n d i t i o n and i n t h e i n e r t atmosphere ( c o n c e n t r a t i o n of oxygen was 0.1 ppm). I n t h e l a t t e r c a s e , because t h e oxygen c o n c e n t r a t i o n was low t h e l o n g e r c o n d i t i o n i n g t i m e a l l o w e d f o r t h e d e t e c t i o n of t h e DTGA formed. The t o t a l amount of TGA (and/or DTGA) a d s o r b e d i n a e r a t e d c o n d i t i o n was a l i t t l e more f o r b o t h c h a l c o p y r i t e and g a l e n a , but remained t h e same as i n t h e n i t r o g e n atmosphere f o r C u - a c t i v a t e d s p h a l e r i t e . The numbers of O residua l TGA A residual DTGA • TGA(DTGA) adsorbed,mole/g 52 0 60 120 180 240 300 Contact Time, min. Fig.24 Concentration of Reaction Product as a Function of Contact Time Under Nitrogen Atmosphere _3 Chalcopyrite/10 M TGA: lg/50ml O r e s i d u a l TGA A r e s i d u a l DTGA O TGA(DTGA) adsorbed, mole/g pH 3.4 _L L_ 240 300 0 60 120 180 Contact Time, min. Concentration of Reaction Product as a Function of Contact Time at Aerated Condition Galena/10~ 3M TGA: 0.8g/50ml O r e s i d u a l TGA A r e s i d u a l DTGA • TGA(DTGA) adsorbed, mole/g 54 10 u CD o a c o •H 4J « U 4-1 e <U o c o u 10 -4 -10 -5 -10 -6 60 120 180 Contact Time, min. 300 F i g . 26 Concentration of Reaction Product as a Function of Contact Time Under Nitrogen Atmosphere Galena/10 _ 3M TGA: 0.8g/50ml O r e s i d u a l TGA A r e s i d u a l DTGA • TGA(DTGA) adsorbed, mole/g 55 300 Contact Time, min. F i g . 27 Concentration of Reaction Product as a Function of Contact Time at Aerated Condition Sphalerite/10~ 3M TGA: lg/50ml O r e s i d u a l TGA A r e s i d u a l DTGA D TGA(DTGA) adsorbed, mole/g 300 Contact Time, min. Fig.28 Concentration of Reaction Product as a Function of Contact Time Under Nitrogen Atmosphere -3 Sphalerite/10 M TGA: lg/50ml O r e s i d u a l TGA A r e s i d u a l DTGA • TGA(DTGA) adsorbed, mole/g e q u i v a l e n t monolayers making up the s u r f a c e c o v e r a g e a t the m i n e r a l s u r f a c e a f t e r 4 hours of c o n d i t i o n i n g , assuming each t h i o g l y c o l l a t e r a d i c a l o c c u p i e d 2 x 1 0 " 1 9 m2 of s u r f a c e s i t e s , were as f o l l o w s : A i r N i t r o g e n C h a l c o p y r i t e 24 18 G a l e n a 28 20 S p h a l e r i t e 5 6 The amount of TGA a d s o r b e d seemed t o r e a c h a maximum v a l u e a f t e r 60 m i n u t e s c o n t a c t . F u r t h e r c o n d i t i o n i n g c a u s e d l i t t l e change. The removal of a d s o r b e d x a n t h a t e a t t h i s f i x e d low pH v a l u e (3.4) was n e g l i g i b l e f o r a l l t h r e e m i n e r a l s . 3.6 . Z e t a P o t e n t i a l s of M i n e r a l s Z e t a p o t e n t i a l s of c h a l c o p y r i t e , g a l e n a and s p h a l e r i t e a r e shown i n F i g s . 29, 30 and 31, r e s p e c t i v e l y . Each p r e s e n t s t h e z e t a p o t e n t i a l s of pure m i n e r a l , m i n e r a l t r e a t e d w i t h e t h y l x a n t h a t e and m i n e r a l t r e a t e d w i t h e t h y l x a n t h a t e p l u s TGA i n s o l u t i o n s open t o a i r . The m i n e r a l s were a l l n e g a t i v e l y c h a r g e d ; t h i s was p o s s i b l y c a u s e d by t h e p r e v i o u s wash w i t h h y d r o c h l o r i c a c i d s o l u t i o n . They became more n e g a t i v e l y c h a r g e d upon t r e a t m e n t by the r e a g e n t s . These o b s e r v a t i o n s i n d i c a t e d t h a t the -90 -80 --70 -F i g . 29 Zeta Potentials of Chalcopyrite vs. pH A chalcopyrite washed with HC1 and water -4 O chalcopyrite + 10 M KEX ' • chalcopyrite + 10 _ 4M KEX + 10~3M TGA +10 PH F i g . 3 0 Zeta P o t e n t i a l s of Galena vs. pH A galena washed w i t h H C 1 and water - 4 O galena +10 M KEX • galena + 1 0 ~ 4 M KEX + 1 0 ~ 3 M TGA -90 " -80 " -70 -o 3 -10 " 0 -+10 I 1 1 I 1 l 1 I 1 I i 1 1 1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 PH Fig.31 Zeta P o t e n t i a l s of Sphalerite vs. pH A Cu-activated s p h a l e r i t e O Cu-activated s p h a l e r i t e + 10~4M KEX r-. -4 -3 • Cu-activated s p h a l e r i t e +10 M KEX + 10 M TGA s p h a l e r i t e were previously treated with Na^S and HC1 ON o a d s o r p t i o n of the t h i o g l y c o l l a t e group onto the n e g a t i v e l y c h a r g e d s u r f a c e was t h r o u g h a c h e m i s o r p t i o n p r o c e s s , a t l e a s t t o t h e f i r s t m o n o l a y e r . I t was n o t e d t h a t t h e shapes of z e t a p o t e n t i a l c u r v e s of m i n e r a l s t r e a t e d by TGA were v e r y s i m i l a r t o t h o s e of the a d s o r p t i o n c u r v e s of TGA o n t o the m i n e r a l s . 3.7 S o l u t i o n Redox P o t e n t i a l and M i n e r a l F l o a t a b i l i t y F i g s . 32 t o 34 show t h e the f l o t a t i o n r e s u l t s of c h a l c o p y r i t e u s i n g d i f f e r e n t d e p r e s s a n t s , t h e samples b e i n g t r e a t e d i n e i t h e r a e r a t e d s o l u t i o n s , o r i n an i n e r t atmosphere ( i n c l u d i n g c o n d i t i o n i n g w i t h x a n t h a t e and d e p r e s s a n t s , and f l o t a t i o n ) . F i g s . 38 t o 40 p r e s e n t t h e f l o t a t i o n r e s u l t s of t h e t h r e e s u l p h i d e m i n e r a l s w i t h TGA as d e p r e s s a n t . I n t h i s s e r i e s of t e s t s , t h e samples were a l l f i r s t c o n d i t i o n e d w i t h x a n t h a t e i n a e r a t e d s o l u t i o n s , then c o n d i t i o n e d w i t h TGA and f l o a t e d under an i n e r t atmosphere. I t i s r a t h e r u n f o r t u n a t e t h a t not enough sample was a v a i l a b l e t o do t h e b l a n k t e s t s ( t e s t s i n t h e absence of d e p r e s s a n t s ) f o r c o m p a r i s o n . From th e p r e v i o u s t e s t r e s u l t s i t can be r e a s o n a b l y s t a t e d t h a t t h e r e c o v e r y and s o l u t i o n redox p o t e n t i a l i n t h e absence of d e p r e s s a n t w i l l be a l l h i g h e r t h a n t h o s e i n t h e p r e s e n c e of t h e d e p r e s s a n t . As can be seen, an i n e r t atmosphere s i g n i f i c a n t l y improved t h e d e p r e s s i v e a c t i o n of sodium s u l p h i d e , but t h e 100 +280 90 80 70 60 * 50 40 30 20 10 +240 4+200 +160 +120 +80 +40 0 -40 -80 -120 -160 -200 -240 -280 -320 7 8 PH 10 11 12 13 F i g . 32 E f f e c t of pH on the Solution Redox P o t e n t i a l and Corresponding Chalcopyrite F l o t a t i o n ( T h i o g l y c o l l i c Acid as Depressant ) _3 xanthated chalcopyrite/10 M TGA: 2g/100ml A A p o t e n t i a l ; # O recovery A # samples xanthated,conditioned and f l o a t e d i n aerated s o l u t i o n s ; A O samples xanthated, con-d i t i o n e d and f l o a t e d under Argon atmosphere 63 100 90 -80 _ 70 -60 u CO g 50 a 01 40 -30 -20 -10 -> s w en CO > •H 4J C CO 4J o a. x o cu 1 2 7 8 PH 10 11 12 13 F i g . 33 E f f e c t of pH on the Solution Redox P o t e n t i a l s and Corresponding Chalcopyrite F l o t a t i o n ( Potassium Cyanide as Depressant ) _3 xanthated chalcopyrite/10 M KCN: 2g/100ml A A p o t e n t i a l ; % O recovery A Q samples xanthated, conditioned and f l o a t e d i n aerated s o l u t i o n s ; A O samples xanthated, con-d i t i o n e d and f l o a t e d under Argon atmosphere 64 > to CO > c u o X o -a cu 10 11 12 13 Fig.34 E f f e c t of pH on the Solution Redox P o t e n t i a l s and Corresponding Chalcopyrite F l o t a t i o n ( Sodium Sulphide as Depressant ) -3 xanthated chalcopyrite/10 M Na 2S: 2g/100ml A A p o t e n t i a l ; % O recovery A % samples xanthated, conditioned and f l o a t e d i n aerated s o l u t i o n s ; A O samples xanthated, conditioned and f l o a t e d under Argon atmosphere +440 +400 +360 +320 i +280 w +240 EC w +200 CO > c CD u r> o-o ~a CD ei +160 +120 +80 +40 0 -40 -80 jr -120 --160 J I i t i i i i 1 2 3 4 5 6 7 8 9 10 11 12 13 pH -3 F i g . 35 Redox P o t e n t i a l s of 10 M T h i o g l y c o l l i c Acid Solutions £ Aerated s o l u t i o n s O Argon-saturated s o l u t i o n s -3 F i g . 36 Redox P o t e n t i a l s of 10 M Potassium Cyanide Solutions | aerated solutions • Argon-saturated solutions +440 -+400 " +360 --40 --80 --120 --160 I * ' i I I i i i i i i I 1 2 3 4 5 6 7 8 9 10 11 12 13 pH -3 Fig.37 Redox P o t e n t i a l s of 10 M Sodium Sulphide Solutions A Aerated s o l u t i o n s A Argon-saturated s o l u t i o n s d e p r e s s i o n by KCN seemed t o be u n a f f e c t e d . T h i o g l y c o l l i c a c i d , on t h e c o n t r a r y , showed r e d u c e d d e p r e s s i v e a c t i o n under an i n e r t atmosphere. T h i s i s most c l e a r l y seen from F i g s . 38 and 40, w hich show f l o t a t i o n w i t h a l l samples x a n t h a t e d i n a e r a t e d s o l u t i o n s but c o n d i t i o n e d and f l o a t e d under d i f f e r e n t a t m o s p h e r i c c o n d i t i o n s . Comparison of F i g s . 35 t o 37 w i t h F i g s . 32 t o 34 i n d i c a t e d t h a t t h e redox p o t e n t i a l s of d e p r e s s a n t s o l u t i o n s were a l l d e c r e a s e d upon a d d i t i o n of ( x a n t h a t e d ) c h a l c o p y r i t e . F i g s . 39 and 40 i n d i c a t e t h a t t h e redox p o t e n t i a l s of TGA s o l u t i o n s d e c r e a s e d upon a d d i t i o n of x a n t h a t e d g a l e n a and x a n t h a t e d s p h a l e r i t e as w e l l (compare F i g . 39 and F i g . 40 w i t h F i g . 3 5 ) . Redox p o t e n t i a l s of t h e m i n e r a l - c o n t a i n i n g s o l u t i o n s were f u r t h e r d e c r e a s e d i n an i n e r t atmosphere. One i n t e r e s t i n g o b s e r v a t i o n was t h a t c o n d i t i o n s under w h i c h x a n t h a t i o n i s c a r r i e d out had a marked i n f l u e n c e on t h e subsequent f l o t a t i o n d e p r e s s i o n . T e s t s w i t h c h a l c o p y r i t e u s i n g TGA as d e p r e s s a n t i n d i c a t e d t h a t samples x a n t h a t e d a t a e r a t e d c o n d i t i o n f l o a t e d b e t t e r , even when the subsequent f l o t a t i o n was p e r f o r m e d i n an i n e r t atmosphere, t h a n samples x a n t h a t e d a t an i n e r t atmosphere and then c o n d i t i o n e d and f l o a t e d a t t h e same atmosphere (see F i g . 4 1 ) . 69 > e w CO co > c u o X o •a OJ F i g . 3 8 E f f e c t of pH on the S o l u t i o n Redox P o t e n t i a l s and Corresponding Chalcopyrite F l o t a t i o n , T h i o g l y c o l l i c Acid as Depressant, A l l Samples Xanthated i n Aerated Solutions xanthated chalcopyrite/10 M TGA: 2g/100ml A A p o t e n t i a l ; # O recovery A 0 samples conditioned and f l o a t e d i n aerated s o l u t i o n s ; A O samples conditioned and f l o a t e d i n Argon-saturated s o l u t i o n s 70 100 90 80 70 60 5-5 ^ 50 u 1) > o o OJ * 40 30 20 10 +280 -I +240 - +200 +160 +120 +80 +40 0 -40 -80 -120 -160 -200 H -240 - -280 -320 w S3 CO CO > o PH o T 3 CD 11 12 13 F i g . 39 E f f e c t of pH on the Solution Redox P o t e n t i a l s and Corresponding Galena F l o t a t i o n , T h i o g l y c o l l i c Acid as Depressant, Samples Xanthated i n Aerated Solutions _3 xanthated galena/10 M TGA: 2g/100ml A A p o t e n t i a l ; # O recovery A % samples conditioned and f l o a t e d i n aerated so l u t i o n s ; A O samples conditioned and f l o a t e d i n Argon-saturated s o l u t i o n s 71 100 7 8 pH ' 10 11 12 13 > e W 3 3 cn co > c cu o o -o 0) F i g . 40 E f f e c t of pH on the Solution Redox P o t e n t i a l s and Corresponding S p h a l e r i t e F l o t a t i o n , T h i o g l y c o l l i c Acid as Depressant, Samples Activated(with copper sulphate) and Xanthated i n Aerated s o l u t i o n _3 sphalerite/10 M TGA: 2g/100ml A A p o t e n t i a l ; # O recovery A 0 samples conditioned and f l o a t e d i n aerated s o l u t i o n s ; A O samples conditioned and f l o a t e d i n Argon-saturated s o l u t i o n s 100 1 2 3 4 5 6 7 8 9 10 11 12 13 pH Fig.41 E f f e c t of Xanthation Condition on Chalcopyrite F l o t a t i o n _3 xanthated chalcopyrite/10 M TGA: 2g/100ml A xanthated i n aerated s o l u t i o n s O xanthated i n Argon-saturated s o l u t i o n s samples conditioned and f l o a t e d under Argon atmosphere 3 .8 I n f r a r e d S p e c t r a The s p e c t r a i n v o l v i n g s u l p h i d e m i n e r a l s were expanded f i v e t i m e s ( i n the t r a n s m i s s i o n r e g i o n of 70-100%) i n o r d e r t o make them more i n d i c a t i v e . G e n e r a l l y , x a n t h a t e showed h i g h l y c h a r a c t e r i s t i c s p e c t r a d u r i n g a d s o r p t i o n on and d e s o r p t i o n from t h e s u r f a c e s ; The s p e c t r a of m i n e r a l s t r e a t e d w i t h TGA were f a r more d i f f i c u l t t o i n t e r p r e t . The s u l p h i d e m i n e r a l samples used f o r making KBr p e l l e t s had been exposed t o t h e oxygenated water f o r s e v e r a l h o u r s ( s e c t i o n 2.5.1), so q u i t e p o s s i b l y t h e y were s e v e r e l y o x i d i z e d . F i g . 42 shows the s p e c t r a of the s u l p h i d e m i n e r a l s a m p l e s , t o g e t h e r w i t h t h o s e of copper s u l p h a t e , l e a d s u l p h a t e and q u a r t z . I t seemed t h a t both c h a l c o p y r i t e and g a l e n a were o x i d i z e d ; t h e y might a l s o c o n t a i n q u a r t z . 3.8.1 S p e c t r a of M e t a l T h i o g l y c o l l a t e s S p e c t r a were o b t a i n e d w i t h KBr p e l l e t s , w h i c h were made by m i x i n g 300 mg KBr w i t h 1 mg of a p r e c i p i t a t e formed i n CuS0 4 and TGA s o l u t i o n s o r w i t h 1 mg of a p r e c i p i t a t e formed i n P b ( N 0 3 ) 2 and TGA s o l u t i o n s . The s p e c t r a , t o g e t h e r w i t h r e f e r e n c e s p e c t r a o f TGA, DTGA and d e u t e r i z e d TGA ( a l l o b t a i n e d by p a s s i n g i n f r a r e d l i g h t t h r o u g h a c a p i l l a r y f i l m between two sodium c h l o r i d e window p l a t e s ) , a r e p r e s e n t e d i n F i g . 43. As seen, a b s o r p t i o n peaks a t 1704 c m - 1 and 1420 c m - 1 i n TGA, whi c h r e p r e s e n t r e s p e c t i v e l y C=0 and C-0 s t r e t c h v i b r a t i o n s i n a c i d c a r b o n y l (COOH) [ 2 7 ] , d i s a p p e a r e d 74 (e) _ l _ _ l _ _ 1 _ 2000 1800 1600 1400 Wavenumber, cm-I 1200 1000 800 F i g . 42 Infrared Spectra of (a) Chalcopyrite, (b) Galena, (c) CuS0 4 5H 20, (d) PbSO^, (e) Quartz. KBr p e l l e t s . 75 100 100 100 100 100 4000 3000 2000 1600 1200 800 400 Kavcnumhcr, cm" F i g . 43 Infrared spectra of (a) copper t h i o g l y c o l l a t e (KBr p e l l e t ) , (b) lead t h i o g l y c o l l a t e (KBr p e l l e t ) , (c) TGA ( c a p i l l a r y f i l m i n NaCl c e l l ) , (d) DTGA ( c a p i l l a r y f i l m i n NaCl c e l l ) , (e) deuterized TGA ( c a p i l l a r y f i l m i n NaCl c e l l ) f r o m t h e s p e c t r a o f c o p p e r t h i o g l y c o l l a t e a n d l e a d t h i o g l y c o l l a t e . T h e s e w e r e g o o d i n d i c a t i o n s t h a t t h e c a r b o x y l g r o u p w a s p r e s e n t i n t h e s a l t a s d i s s o c i a t e d a n i o n , C O O - , a h i g h l y r e s o n a n c e - s t a b i l i z e d s t r u c t u r e i n w h i c h t h e t w o c a r b o n - o x y g e n b o n d s w e r e i d e n t i c a l ( s e c t i o n 1 . 1 . 4 ) . C o n s e q u e n t l y , t h e a b s o r p t i o n p e a k s o f C = 0 a n d C - 0 d i s a p p e a r e d a n d t h o s e p r e s e n t w e r e t h e a s y m m e t r i c a l s t r e t c h i n g v i b r a t i o n o f t h i s C O O - ( 1 5 7 2 c m - 1 f o r c o p p e r s a l t a n d 1 5 3 1 c m - 1 f o r t h e l e a d s a l t ) a n d t h e s y m m e t r i c a l s t r e t c h i n g v i b r a t i o n o f t h e g r o u p a t a r o u n d 1 3 5 0 c m - 1 . I t i s a l s o n o t e d t h a t t h e a b s o r p t i o n p e a k o f m e r c a p t o g r o u p S - H a t 2 5 6 7 c m - 1 d i s a p p e a r e d f r o m t h e s p e c t r a o f t h e s a l t s . T h i s i n d i c a t e d t h a t e i t h e r t h e T G A h a d b e e n o x i d i z e d i n t h e s a l t f o r m a t i o n p r o c e s s ( s e e t h e s a m e f i g u r e f o r t h e s p e c t r u m o f D T G A ) , o r t h e m e t a l i o n s h a d r e p l a c e d t h e p r o t o n b o n d e d t o t h e s u l p h u r . T h i s w i l l b e f u r t h e r d i s c u s s e d l a t e r . 3.8.2 S p e c t r a o f C h a l c o p y r i t e T h e c h a l c o p y r i t e s a m p l e , w h e n t r e a t e d w i t h p o t a s s i u m e t h y l x a n t h a t e s h o w e d t y p i c a l a b s o r p t i o n p e a k s o f c u p r o u s e t h y l x a n t h a t e a t 1 1 8 3 , 1117 a n d 1030 c m - 1 [ 2 9 ] . A s m a l l a b s o r p t i o n p e a k a t 1217 c m - 1 m i g h t i n d i c a t e t h e p r e s e n c e o f d i x a n t h o g e n ( s e e F i g . 4 4 ( b ) ) . S u b s e q u e n t t r e a t m e n t b y T G A a t p H 6 . 3 d i d n o t r e m o v e t h e a b s o r p t i o n p e a k s b u t a t p H 1 1 . 5 , t h e i n t e n s i t i e s o f t h e C u E t X a b s o r p t i o n p e a k s w e r e r e d u c e d s i g n i f i c a n t l y ( s e e F i g . 4 4 ( d ) ) . T h i s f i g u r e a l s o s h o w s 77 F i g . 44 Infrared spectra of (a) c h a l c o p y r i t e , and c h a l c o p y r i t e (b) treated with KEX (pH 6.3), (c) treated with KEX (pH 6.3), then with TGA (pH 6.3), (d) treated with KEX (pH 6.3), then with TGA (pH 11.5). (e) reference spectrum of CuEX + ( E X ^ , (f) reference spectrum of copper t h i o g l y c o l l a t e . KBr p e l l e t a b s o r p t i o n peaks a t 1719, 1434 and 1295 c m - 1 , whi c h i n d i c a t e d t h e p r e s e n c e of TGA; and a b s o r p t i o n peaks a t 1561 and 1342 cm" 1, which i n d i c a t e d t h e p r e s e n c e of copper t h i o g l y c o l l a t e . The s p e c t r u m of pure c h a l c o p y r i t e t r e a t e d by TGA showed t h e a b s o r p t i o n peaks of b o t h TGA and copper t h i o g l y c o l l a t e (see F i g . 4 5 ( b ) ) . Subsequent t r e a t m e n t of t h i s T G A - t r e a t e d c h a l c o p y r i t e by p o t a s s i u m e t h y l x a n t h a t e a t pH 6.2 ca u s e d the a p p e a r a n c e of t h r e e i n t e n s i v e c h a r a c t e r i s t i c a b s o r p t i o n peaks of c u p r o u s e t h y l x a n t h a t e ( F i g . 4 5 ( c ) ) . 3.8.3 S p e c t r a of S y n t h e t i c ZnS Copper a c t i v a t e d s y n t h e t i c ZnS, when r e a c t e d w i t h p o t a s s i u m e t h y l x a n t h a t e showed a b s o r p t i o n peaks a t 1193, 1117 and 103.1 c m - 1 , w h i c h were t y p i c a l of c u p r o u s e t h y l x a n t h a t e . These a b s o r p t i o n peaks were not removed a t pH 6.3 by TGA b u t were a l m o s t t o t a l l y removed a t pH 11.9 ( F i g . 4 6 ( d ) ) . F i g . 47 shows t h a t e t h y l x a n t h a t e a d s o r b s onto t h e T G A - t r e a t e d ZnS s u r f a c e (pH 7.5). The p r e s e n c e of e i t h e r TGA or t h i o g l y c o l l a t e on t h i s ZnS s u r f a c e was r a t h e r d i f f i c u l t t o d i s t i n g u i s h from t h e s p e c t r a shown i n F i g . 47. 3.8.4 S p e c t r a of Ga l e n a F i g . 48 p r e s e n t s s p e c t r a of g a l e n a t r e a t e d w i t h r e a g e n t s of c o n c e n t r a t i o n of 0.001M i n s t e a d of 0.01M. T h i s l ower c o n c e n t r a t i o n was used because i t seemed t h a t among 79 F i g . 45 Infrared spectra of (a) c h a l c o p y r i t e , and c h a l c o p y r i t e (b) treated with TGA (pH 5 .2 ) , (c) treated with TGA (pH 5.2), then with KEX (pH 6.2). (d) reference spec-trum of copper t h i o g l y c o l l a t e . (e) reference spectrum of CuEX + ( E X ) 7 . KBr p e l l e t 80 Fig. 46 Infrared Spectra of (a) synthetic ZnS, and Cu-activated synthetic ZnS treated (b) with KEX (pH 6.3), (c) treated with KEX (pH 6.3), then with TGA (pH6.3), (d) treated with KEX (pH 6.3), then with TGA (pH 11.9). (e) reference spectrum of CuEX + (EX)^. (f) reference spectrum of copper thioglycollate. KBr pellet. 81 (a) \ / \ / *0 in © O CN \ V \ / m © ^ 00 00 | ( c ) * \ / 2 2 s 2 2 lHil/wi <a 1 o KCR i ~t «-* / M / * — n 0"> CO (d) ~ , y / ^ ^ S / / / ^ ^ \ m / r- - i \ - y •» * -» r. 1 / 1 / ° l / (e) ~ " S3 !/ 3lf » Ox ^ I I 1 1 1 1 1 1 1 - 10^0^"""""^^ 2000 1800 1600 1400 1200 1000 800 Wavenumber, cm F i g . 47 Infrared Spectra of (a) synthetic ZnS, and Cu-activated synthetic ZnS treated (b) with TGA (pH 7.5), (c) with TGA (pH 7.5), then with KEX (pH7.5). (d) reference spectrum of copper t h i o g l y c o l l a t e . (e) reference spectrum of CuEX + (EX),. KBr p e l l e t . 82 i i i i i i i i i i i 2000 1800 1600 1400 1200 1000 800 Wavenumber, cm F i g . 48 Infrared spectra of (a) galena, and galena (b) treated with KEX (pH 6.6), (c) treated with KEX (pH 6.6), then with TGA (pH 6.6), (d) treated with KEX (pH 6.6), then with TGA (pH 9.8). (e) reference spectrum of lead e t h y l xanthate. (f) reference spectrum of lead t h i o g l y c o l l a t e . KBr p e l l e t t h e t h r e e s u l p h i d e m i n e r a l s t e s t e d , g a l e n a was most r e s p o n s i v e t o b o t h KEX and TGA. A b s o r p t i o n peaks t y p i c a l of l e a d e t h y l x a n t h a t e a t 1198,1108 and 1016 cm" 1 appeared upon t r e a t m e n t by KEX, and subsequent t r e a t m e n t by TGA a l m o s t t o t a l l y removed t h e s e a b s o r p t i o n peaks even a t pH 6.6. These i n f r a r e d s p e c t r a c o i n c i d e w e l l w i t h the H a l l i m o n d Tube f l o t a t i o n r e s u l t s which showed t h a t g a l e n a was t o t a l l y d e p r e s s e d a t v e r y low pH v a l u e s ( s e e F i g . 1 3 ) . F i g . 49(b) p r e s e n t s the s p e c t r u m of g a l e n a t r e a t e d w i t h 0.01M TGA s o l u t i o n . As s e e n , t h r e e s u c c e s s i v e a b s o r p t i o n peaks a t 1557,1365 and 1218 cm" 1 showed c l e a r l y the p r e s e n c e of l e a d t h i o g l y c o l l a t e ( r e f e r t o F i g . 4 9 ( d ) ) . For t h i s T G A - t r e a t e d g a l e n a sample, when r e a c t e d w i t h 0.001M KEX a t pH 5.2, l e a d e t h y l x a n t h a t e was p r o d u c e d on t h e s u r f a c e and t h e a d s o r b e d l e a d t h i o g l y c o l l a t e was s i g n i f i c a n t l y removed ( F i g . 4 9 ( c ) ) . T h i s r e s u l t , a t f i r s t s i g h t , d i d not seem t o c o i n c i d e w i t h t h e f l o t a t i o n r e s u l t of g a l e n a . F i g . 16 shows t h a t g a l e n a was t o t a l l y d e p r e s s e d a t t h i s c o n d i t i o n . The r e a s o n f o r t h e d i s c r e p a n c y was p r o b a b l y t h a t t h e f l o t a t i o n was p e r f o r m e d i n t h e p r e s e n c e of both p o t a s s i u m e t h y l x a n t h a t e and t h i o g l y c o l l i c a c i d i n t h e s o l u t i o n , whereas t h e i n f r a r e d s p ectrum was r e c o r d e d u s i n g a f i l t e r e d and d r i e d T G A - t r e a t e d g a l e n a sample so t h a t t h e t h i o g l y c o l l i c a c i d was a b s e n t from t h e p o t a s s i u m e t h y l x a n t h a t e s o l u t i o n . 84 . (a) s 1 o o ^"^*^\ / \ / CO <N » \ ' (b) \ y \ / 3- " /• \ l \ / \ I V ° s • • ft1 / vO CO [ r>4 CO Jo 1 (M CO (d) \ / ^ V 2 \ t~t! r . ~ i \ in/ .o rg fM ' \ /Vi / i i i i i i i i i r 1 en i o> i 0 3 -4 2000 1800 1600 U00 1200 1000 800 Wavenumber, cm ^ Fig . 49 Infrared spectra of (a) galena, and galena (b) treated with TGA (0.01M, pH 5), (c) treated with TGA (0.01M, pH 5) , then with KEX (0.001M, pH 5.2). (d) reference spectrum of lead t h i o g l y c o l l a t e . (e) reference spec-trum of lead ethyl xanthate. KBr. p e l l e t 3,8.5 R e f l e c t a n c e S p e c t r a As mentioned p r e v i o u s l y , r e f l e c t a n c e s p e c t r a were r e c o r d e d w i t h an i n t e r n a l r e f l e c t i o n e l e m e n t — a ZnS p r i s m . S i n c e t h i s p r i s m a b s o r b e d i n c i d e n t i n f r a r e d l i g h t c o m p l e t e l y i n t h e range 1850 c m - 1 t o 1650 c m - 1 , t h e d e t e c t i o n of t h i o g l y c o l l a t e on t h e p r i s m s u r f a c e became v e r y d i f f i c u l t . S p e c t r a were r e c o r d e d o n l y i n t h e range 1300 t o 1000 cm" 1, as shown i n F i g . 50 and F i g . 51. S p e c t r a v e r y s i m i l a r t o t h o s e of the r e f e r e n c e t r a n s m i s s i o n s p e c t r a were o b s e r v e d . A b s o r p t i o n peaks t y p i c a l of c u p r o u s e t h y l x a n t h a t e a t 1197,1118 and 1032 cm' 1 and a b s o r p t i o n peaks t y p i c a l of d i x a n t h o g e n a t 1239 and 1268 c m - 1 a p p e a r e d when t h e CuSO«-treated ZnS p r i s m was p l a c e d i n 0.001M KEX s o l u t i o n f o r 4 h o u r s ( F i g . 5 0 ( a ) ) . These a b s o r p t i o n peaks were not s i g n i f i c a n t l y removed a t pH 6.1 by r e a c t i n g w i t h 0.001M TGA even a f t e r a 4 hour c o n t a c t , but were removed a t pH 11.7. F i g . 51 shows t h e a d s o r p t i o n of p o t a s s i u m e t h y l x a n t h a t e on t h e TGA t r e a t e d p r i s m s u r f a c e . A f t e r . r e a c t i o n f o r one hour, t h e p r e s e n c e of c u p r o u s e t h y l x a n t h a t e on the s u r f a c e became c l e a r and a f t e r f o u r h o u r s r e a c t i o n , d i x a n t h o g e n i s formed on t h e s u r f a c e as w e l l as c u p r o u s e t h y l x a n t h a t e . 86. s o •rt 4J a. u o cn <: 1300 1200 Wav enum b er, cm 1100 -1 1000 (c) ZnS prism a c t i v a t e d with copper and con-tacted with KEX f o r 4 hours, then r e a c t -ed f o r 4 hours with TGA at pH 11.7 . (b) ZnS prism a c t i v a t e d with copper and con-tacted with KEX f o r 4 hours, then r e a c t -ed for 4 hours with TGA at pH 6.1 . (a) ZnS prism a c t i v a t e d with copper and then reacted with KEX f o r 4 hours at pH 6.5 ( n a t u r a l pH ). F i g . 50 Infrared Spectra of ZnS Prism Treated with KEX, then with TGA. ATR. 87 o m o oo i-i I - J i I 1300 1200 1100 1000 Wavenumber, cm ^ F i g . 51 Infrared Spectra of (a) CuEX + (EX> 2 (KBr p e l l e t ) , and ZnS prism a c t i v a t e d by Cu, contacted with TGA fo r 4 hours and then reacted with KEX f o r (b) 1 hour, (c) 4 hours at pH 6. ATR. 3.8.6 M i s c e l l a n e o u s S p e c t r a F i g . 52 p r e s e n t s s p e c t r a of c o p p e r t h i o g l y c o l l a t e r e a c t e d w i t h 0.001M KEX s o l u t i o n . A b s o r p t i o n peaks t y p i c a l of c u prous e t h y l x a n t h a t e a p p e a r e d a f t e r 30 m i n u t e s c o n t a c t w i t h the s o l u t i o n but t h e a b s o r p t i o n peak a t 1030 cm" 1 i s b r o a d e r and s h i f t e d a l i t t l e t o a lo w e r f r e q u e n c y . S p e c t r a were a l s o r e c o r d e d w i t h c u p r o u s e t h y l x a n t h a t e p r e c i p i t a t e s samples r e a c t e d w i t h 0.001M TGA s o l u t i o n , b u t no change i n th e s p e c t r a was o b s e r v e d even a f t e r 60 m i n u t e s c o n t a c t (see F i g . 5 3 ) . 3.9 D i f f e r e n t i a l F l o t a t i o n o f S y n t h e t i c M i n e r a l M i x t u r e s A wide pH r e g i o n f o r p o s s i b l e s e l e c t i v e s e p a r a t i o n was seen i n t h e s i n g l e m i n e r a l f l o t a t i o n o f c h a l c o p y r i t e and g a l e n a u s i n g TGA as d e p r e s s a n t ( F i g . 12 and 13). An attempt was t h e n made t o s e p a r a t e s y n t h e t i c m i x t u r e s of t h e same m i n e r a l s . The f l o t a t i o n s e p a r a t i o n was p e r f o r m e d u s i n g a P/S c e l l a t a n i t r o g e n f l o w r a t e of 30 ml p e r m i n u t e , w i t h f l o t a t i o n f o r one minute when t h e d e p r e s s a n t c o n c e n t r a t i o n was 10"*M, and two mi n u t e s when i t was 10" 3M. The mixed m i n e r a l s e p a r a t i o n r e s u l t s , as shown i n F i g . 54 were not so e n c o u r a g i n g , however. S i m i l a r t e s t s were c o n d u c t e d w i t h p o t a s s i u m c y a n i d e and sodium s u l p h i d e as d e p r e s s a n t s ( F i g . 55 and 5 6 ) . I t was o b s e r v e d t h a t o n l y c y a n i d e c o u l d make a s a t i s f a c t o r y s e p a r a t i o n , a l t h o u g h t h e pH range a t which s e p a r a t i o n was e f f e c t e d was v e r y narrow ( F i g . 5 5 ) . 89 F i g . 52 Infrared spectra of (a) copper t h i o g l y c o l l a t e , and copper t h i o g l y c o l l a t e treated with 0.001M KEX at pH 6.5 f o r (b) 10 min. (c) 30 min. (d) 60 min. (e) reference spectrum of CuEX + (EX) . KBr p e l l e t 90 F i g . 53 Infrared Spectra of (a) CuEX + (EX) 2, (b) CuEX + (EX> 2 reacted with 0.001M TGA s o l u t i o n f o r 60 minutes at pH 3.5. KBr p e l l e t . 100 90 -80 . 70 " 60 ' 50 ' 40 " 30 -20 -10 -10 11 12 pH F i g . 54 F l o t a t i o n Separation of Synthetic Chalcopyrite-Gal Mixtures with T h i o g l y c o l l i c Acid -4 chalcopyrite/galena/10 M KEX: lg/lg/lOOml A A recovery of c h a l c o p y r i t e # O recovery of galena • • 10 M TGA; A O 10 M TGA 100 90 " 80 ~ 70 -60 -50 -40 -30 -20 -10 . X 7 8 pH 10 11 12 13 F i g . 55 F l o t a t i o n Separation of Synthetic Chalcopyrite-Galena Mixtures with Potassium Cyanide -4 chalcopyrite/galena/10 M KEX: lg/lg/lOOml A recovery of c h a l c o p y r i t e O recovery of galena -3 concentration of KCN: 10 M 1 2 3 4 5 6 7 8 9 10 11 12 13 pH F i g . 56 F l o t a t i o n Separation of Synthetic Chalcopyrite-Galena Mixtures with Sodium Sulphide chalcopyrite/galena/10 M KEX: lg/lg/lOOml • • 10 _ 4M Na 2S; A O 10 _ 3M Na 2S A A recovery of c h a l c o p y r i t e # O recovery of galena 93a C h a l c o p y r i t e - s p h a l e r i t e s e p a r a t i o n s were p e r f o r m e d , a t d i f f e r e n t l e v e l s of s p h a l e r i t e a c t i v a t i o n . As seen i n F i g . 57, a t a f i x e d pH of 10.5, when t h e r e was no a c t i v a t i o n of s p h a l e r i t e , t h e s e p a r a t i o n was s h a r p . But the d i f f e r e n c e s i n f l o a t a b i l i t i e s d i m i n i s h e d r a p i d l y w i t h t h e i n c r e a s e i n t h e l e v e l of c o p p e r a c t i v a t i o n of s p h a l e r i t e . F i g s . 58 and 59 show t h a t w i t h a copper c o n c e n t r a t i o n of 10" 5M, f a i r l y good s e p a r a t i o n c o u l d be a c h i e v e d i n a wide range of pH v a l u e s but w i t h a c o p p e r c o n c e n t r a t i o n of 2x10""M, the s e p a r a t i o n was not good a t a l l . 0 1 2 3 Cu-coverage on S p h a l e r i t e , monolayer Fig.57 F l o t a t i o n Separation of Synthetic Mixtures of Chalcopyrite and Cu-activated S p h a l e r i t e -4 c h a l c o p y r i t e / s p h a l e r i t e / 1 0 M KEX: lg/lg/lOOml A recovery of c h a l c o p y r i t e O recovery of a c t i v a t e d s p h a l e r i t e concentration of TGA: 10 M^ 95 2 3 4 5 6 7 8 9 10 11 12 13 PH F i g . 58 F l o t a t i o n Separation of Synthetic Mixtures of Chalcopyrite and S p h a l e r i t e Activated with 10 M^ Copper Sulphate Solution -4 c h a l c o p y r i t e / s p h a l e r i t e / 1 0 M KEX: lg/lg/lOOml A recovery of c h a l c o p y r i t e O recovery of s p h a l e r i t e concentration of TGA: 10 ~*M PH 59 F l o t a t i o n Separation of Synthetic Mixtures of Chalcopyrite -4 and S p h a l e r i t e Activated with 2x10 M Copper Sulphate -4 c h a l c o p y r i t e / s p h a l e r i t e / 1 0 M KEX: lg/lg/lOOml A recovery of c h a l c o p y r i t e Q recovery of s p h a l e r i t e concentration of TGA: 10 M^ CHAPTER 4 DISCUSSION 4.1 S t r u c t u r e of T h i o g l y c o l l a t e S a l t S i n c e b o t h t h e mercapto group and t h e c a r b o x y l group of t h e TGA m o l e c u l e p o s s e s s a c i d i c p r o p e r t i e s and b o t h a r e c h e m i c a l l y r e a c t i v e , when m e t a l i o n s a r e r e a c t e d w i t h TGA t o form a s a l t , bonding c o u l d o c c u r t h r o u g h e i t h e r one of t h e g r o u p s , o r t h r o u g h b o t h . I t has been seen from F i g . 43 t h a t t h e a b s o r p t i o n peak of t h e mercapto group d i s a p p e a r s from t h e IR s p e c t r a of t h e copper and l e a d s a l t s . T h i s i n d i c a t e s t h a t a l t h o u g h not d i s s o c i a t e d i n aqueous s o l u t i o n s , t h e p r o t o n i n t h e mercapto group c o u l d have been s u b s t i t u t e d by m e t a l i o n s . On t h e o t h e r hand, t h e s p e c t r a of s a l t s i n d i c a t e t h e d i s a p p e a r a n c e of t h e c a r b o n y l group a b s o r p t i o n peak, and show t h e s y m m e t r i c a l and a s y m m e t r i c a l s t r e t c h i n g of t h e r e s o n a n c e - s t a b i l i z e d COO" group. T h i s c o u l d be caused by t h e pure i o n i z e d c a r b o x y l g r o u p , o r by a c a r b o x y l - m e t a l b o n d i n g . K a g a r i s e [30] has found t h a t t h e r e i s a d i r e c t r e l a t i o n s h i p between t h e a s y m m e t r i c a l s t r e t c h i n g f r e q u e n c y and t h e e l e c t r o n e g a t i v i t y of t h e m e t a l i o n s bonded t o the c a r b o x y l g r o u p s . S i n c e copper and l e a d i o n s have d i f f e r e n t e l e c t r o n e g a t i v i t i e s (1.9 f o r copper and 1.8 f o r l e a d [ 3 1 ] ) , and d i f f e r e n t a s y m m e t r i c a l s t r e t c h i n g f r e q u e n c i e s have been o b s e r v e d , /.e.,1572 c m - 1 f o r copper t h i o g l y c o l l a t e and 1531 c m - 1 f o r l e a d t h i o g l y c o l l a t e , i t can be s a i d t h a t t h e s e m e t a l i o n s have a l s o bonded t o c a r b o x y l group. The s t o i c h i o m e t r i c r e a c t i o n t e s t s showed t h a t i n an a c i d i c e n v ironment i n which t h e m e t a l s a r e p r e s e n t as i o n s , f o r e v e r y TGA m o l e c u l e r e a c t e d , one m e t a l i o n was consumed. S i n c e t h e m e t a l i o n s a r e d i v a l e n t , i n o r d e r t o m a i n t a i n t h e o v e r a l l n e u t r a l i t y of t h e s o l u t i o n , t h e TGA m o l e c u l e s h o u l d a c t as d i v a l e n t as w e l l . T h i s i n d i c a t e s t h a t the u n i v a l e n t c a r b o x y l group and mercapto group a r e b o t h p a r t i c i p a t i n g i n the p r e c i p i t a t i o n r e a c t i o n s , w h i c h i n t u r n means t h a t t h e m e t a l i o n s a r e l i k e l y bonded t o b o t h c a r b o x y l and mercapto g r o u p s . I n t h e c a s e of copper t h i o g l y c o l l a t e , i t was o b s e r v e d t h a t s l i g h t l y more copper i o n s were consumed than would be i n d i c a t e d by a 1:1 s t o i c h i o m e t r y ( T a b l e I I I ) . T h i s may be due t o t h e f a c t t h a t TGA i s a r e d u c i n g a g e n t , w h i c h , when mixed w i t h copper s u l p h a t e , r e d u c e s some C u + + i o n s t o Cu*, so t h a t some of t h e s a l t was i n t h e form: CuOOCH 2CS-Cu-SCH 2COOCu and t h i s r e q u i r e s more copper i o n s t o be consumed th a n t h e u n i t s t o i c h i o m e t r i c a l r a t i o . 4.2 A d s o r p t i o n Mechanisms of TGA 4.2.1 D e p r e s s i v e - R e s p o n s i b l e S p e c i e s of TGA I t i s n o t e d t h a t t h e f l o a t a b i l i t i e s of s u l p h i d e m i n e r a l s m o d i f i e d by TGA d e c r e a s e r a p i d l y i n a narrow pH range then l e v e l o f f w i t h t h e i n c r e a s e i n pH ( s e c t i o n 3.3). I f t h e s e pH v a l u e s a r e t a k e n as c r i t i c a l pH v a l u e s t o p r e v e n t the c o n t a c t between gas b u b b l e s and m i n e r a l p a r t i c l e s , t h e n t h e s o - c a l l e d " c o n t a c t c u r v e " can be drawn. T h i s i s shown i n F i g . 60. Compared w i t h F i g . 1, t h e c o n t a c t c u r v e of sodium s u l p h i d e , i t i s seen t h a t t h e d e p r e s s i v e a c t i o n s of t h e two r e a g e n t s a r e v e r y s i m i l a r . S i n c e the a c t u a l d e p r e s s i v e s p e c i e s i n sodium s u l p h i d e i s SH" ( s e c t i o n 1.1.2), from t h i s s i m i l a r b e h a v i o u r , t h e mercapto group i n TGA m o l e c u l e i s s u s p e c t e d t o be t h e s p e c i e s r e s p o n s i b l e f o r t h e d e p r e s s i o n . More c o n v i n c i n g e v i d e n c e i s seen from t h e c o m p a r i s o n t e s t between TGA and GA. I n s e c t i o n 3.3, i t has been shown t h a t u n l i k e TGA, GA has no d e p r e s s i v e a c t i o n on t h e s u l p h i d e m i n e r a l s . GA has t h e c h e m i c a l f o r m u l a : HOCH2COOH. The o n l y d i f f e r e n c e between th e two r e a g e n t s i s t h a t GA has a h y d r o x y l group a t t a c h e d t o t h e -CH 2- group whereas TGA has a mercapto group a t t a c h e d t o t h e -CH 2- group. So t h e d i f f e r e n t d e p r e s s i v e b e h a v i o u r i s s o l e l y d e t e r m i n e d by the p r e s e n c e or absence of t h e mercapto g r o u p . 1 2 0 SULPHIDE. / MINERAL / 0^C-CH2-S-S-CH2 °5C-CH 2 -S-H-^C-CH 2 -S-H S-CH 2 -C^: H H . ;>-CH 2 -S-S-CH 2 S-CH2-C^]..H-S-CH2-C^] S - C H 2 - < : H H . > - C H 2 - S - H Fig.61 Schematic Diagram of the P o s s i b l e Adsorption Model of T h i o g l y c o l l i c Acid onto Sulphide Mineral Surface 101 4.2.2 A d s o r p t i o n of TGA I t has been d i s c u s s e d i n s e c t i o n 4.1 t h a t m e t a l i o n s can be bonded t o b o t h mercapto and c a r b o x y l g r o u p s , w h i c h i m p l i e s t h a t a TGA m o l e c u l e can be a d s o r b e d onto t h e s u l p h i d e m i n e r a l s u r f a c e t h r o u g h a mercapto gro u p , o r t h r o u g h a c a r b o x y l group, or t h r o u g h b o t h . The TGA m o l e c u l e s a d s o r b e d o n t o the m i n e r a l s u r f a c e t h r o u g h b o t h of t h e groups form an " a r c h " on t h e m i n e r a l s u r f a c e , e x p o s i n g t h e -CH 2- group t o t h e s u r r o u n d i n g s . S i n c e t h i s form of a d s o r p t i o n i s not l i k e l y t o be e i t h e r s t r o n g l y h y d r o p h o b i c nor s t r o n g l y h y d r o p h i l i c , i t w i l l not s i g n i f i c a n t l y a f f e c t the f l o a t a b i l i t i e s of s u l p h i d e m i n e r a l s . F u r t h e r m o r e , t h e f o r m a t i o n o f subsequent m u l t i l a y e r c o v e r a g e o n t o t h i s " a r c h " i s r a t h e r u n l i k e l y . I t t h u s seems t h a t t h i s form of a d s o r p t i o n does not c o n t r i b u t e much t o t h e o v e r a l l a d s o r p t i o n and d e p r e s s i v e a c t i o n of TGA. The TGA m o l e c u l e s a d s o r b e d t h r o u g h the c a r b o x y l group w i l l not c a u s e d e p r e s s i o n i n t h e x a n t h a t e s o l u t i o n . Because i f t h e y d i d , g l y c o l l i c a c i d , w h i c h can a l s o be a d s o r b e d o n t o the m i n e r a l s u r f a c e t h r o u g h the c a r b o x y l g r o u p , would be e x p e c t e d t o show a s t r o n g e r d e p r e s s i v e a c t i o n t h a n t h i o g l y c o l l i c a c i d . T h i s i s not t h e c a s e . A c t u a l l y , t h e c a r b o x y l - g r o u p - b o n d e d TGA i s d i s p l a c e d by the subsequent t r e a t m e n t w i t h e t h y l x a n t h a t e , and t h i s i s most c l e a r l y seen from F i g . 49. Onl y t h e mercapto-group-bonded TGA can be f i r m l y a d s o r b e d on t h e s u r f a c e , and d i s p l a c e a d s o r b e d x a n t h a t e o r compete f o r s u r f a c e s i t e s w i t h x a n t h a t e . The a d s o r p t i o n t h r o u g h t h e c a r b o x y l group o r t h r o u g h th e mercapto group c o u n t s f o r the f i r s t c h e m i s o r b e d m o n o l a y e r . Subsequent a d s o r p t i o n onto t h i s l a y e r can be t h r o u g h hydrogen b o n d i n g and t h r o u g h -S-S- bondi n g (dimer f o r m a t i o n ) due t o o x i d a t i o n ( F i g . 6 1 ) . I t i s n o t e d t h a t t h i s a d s o r p t i o n model i s d i f f e r e n t from t h e one pro p o s e d by Raghavan and Unger [ 3 ] , who s u g g e s t e d a c o n s t a n t c o v e r a g e o f TGA a t a c h a l c o c i t e s u r f a c e and t h e DTGA, which was formed by t h e i n t e r a c t i o n of aqueous TGA w i t h a d s o r b e d TGA on t h e s u r f a c e , went i n t o s o l u t i o n i n s t e a d of r e m a i n i n g on t h e s u r f a c e . 4.3 E f f e c t of Oxygen The e x p e r i m e n t a l r e s u l t s i n d i c a t e t h a t a h i g h e r oxygen c o n c e n t r a t i o n i n s o l u t i o n c a u s e s more r e s i d u a l DTGA t o be pr o d u c e d and enhances t h e a d s o r p t i o n of TGA and/or DTGA. The p r o d u c t i o n of DTGA i s not s u r p r i s i n g , but t h e enhanced a d s o r p t i o n , a t f i r s t s i g h t , i s not so o b v i o u s . I t i s g e n e r a l l y t hought t h a t t h e o x i d i z e d d i m e r , DTGA, w i l l be a d s o r b e d o n l y t h r o u g h a p h y s i c a l b o n d i n g of some s o r t , w h i c h would not be as s t r o n g as a c h e m i s o r p t i o n . C o n s i d e r i n g t h e model p r o p o s e d i n t h e p r e v i o u s s e c t i o n , i n which a c h e m i s o r b e d TGA monolayer i s c o v e r e d by TGA m o l e c u l e s t h r o u g h hydrogen b o n d i n g and by DTGA m o l e c u l e s t h r o u g h -S-S-b o n d i n g , i t becomes c l e a r t h a t an o x i d a t i v e e n v i r o n m e n t , such as a h i g h e r oxygen c o n c e n t r a t i o n , w i l l enhance t h e m u l t i l a y e r a d s o r p t i o n of t h i o g l y c o l l i c a c i d due t o the f a c i l i t a t e d DTGA dimer f o r m a t i o n . T h i s a l s o e x p l a i n s why, u n l i k e sodium s u l p h i d e which shows a s i g n i f i c a n t l y improved d e p r e s s i o n i n o x y g e n - d e f i c i e n t c o n d i t i o n ( F i g . 3 4 ) , t h e d e p r e s s i v e a c t i o n of TGA i s not r e d u c e d by the p r e s e n c e of oxygen but on t h e c o n t r a r y , seems t o become even more e v i d e n t (see F i g . 38 and F i g . 4 0 ) . The i n t e r e s t i n g r e s u l t i s t h a t t h i s improved d e p r e s s i v e a c t i o n of TGA i n a i r i s o b s e r v e d w i t h c h a l c o p y r i t e and C u - a c t i v a t e d s p h a l e r i t e , b o t h of whi c h have been shown t o produce l a r g e amounts of r e s i d u a l DTGA i n e x c e s s of r e s i d u a l TGA i n a e r a t e d s o l u t i o n s (see F i g . 23 and F i g . 2 7 ) . 4.4 S e l e c t i v i t y S i n c e TGA f u n c t i o n s much l i k e h y d r o s u l p h i d e , HS", which i s a d e p r e s s a n t f o r a l m o s t a l l s u l p h i d e m i n e r a l s , t h e s e l e c t i v e s e p a r a t i o n of s u l p h i d e m i n e r a l s u s i n g TGA i s not p r o m i s i n g , as o b s e r v e d i n t h e d i f f e r e n t i a l f l o t a t i o n t e s t s . But s i n c e i t i s l e s s t o x i c than c y a n i d e and l e s s a f f e c t e d by o x i d a t i o n than sodium s u l p h i d e o r h y d r o s u l p h i d e , i t can be used t o r e p l a c e t h e s e r e a g e n t s i n c e r t a i n s i t u a t i o n s . CHAPTER 5 CONCLUSIONS The e n v i r o n m e n t a l c o n t r o l p o l i c i e s and c o s t c o n s i d e r a t i o n s , r e s u l t i n g from w a s t e f u l c o n s u m p t i o n of r e a g e n t s , l i m i t t h e use of i n o r g a n i c d e p r e s s a n t s . As a r e s u l t , a l a r g e v a r i e t y o f o r g a n i c d e p r e s s a n t s have r e c e n t l y been d e v e l o p e d . Among them, t h i o g l y c o l l i c a c i d , o r t h i o g l y c o l l a t e , has been s u c c e s s f u l l y used i n s e v e r a l Cu-Mo f l o t a t i o n p l a n t s . T h i s e x p e r i m e n t a l work was c o n d u c t e d w i t h t h e aims o f d e v e l o p i n g a b a s i c u n d e r s t a n d i n g of t h e d e p r e s s i v e mechanisms of t h i o g l y c o l l i c a c i d , and s e a r c h i n g f o r p o t e n t i a l u s e s of t h i s r e a g e n t as a s e l e c t i v e d e p r e s s a n t . T h i s work has r e s u l t e d i n t h e f o l l o w i n g c o n c l u s i o n s : a. T h i o g l y c o l l i c a c i d shows s t r o n g d e p r e s s i v e a c t i o n on the s u l p h i d e m i n e r a l s * t e s t e d , w i t h t h e most marked e f f e c t on g a l e n a . b. When e t h y l x a n t h a t e - t r e a t e d s u l p h i d e m i n e r a l s a r e * In t h i s s e c t i o n , " s u l p h i d e m i n e r a l s " r e f e r t o c h a l c o p y r i t e , g a l e n a and C u - a c t i v a t e d s p h a l e r i t e . s u b j e c t t o t r e a t m e n t by t h i o g l y c o l l i c a c i d i n an a l k a l i n e s o l u t i o n , t he a d s o r b e d e t h y l x a n t h a t e i s d e s o r b e d . T h i o g l y c o l l i c a c i d e x h i b i t s m u l t i l a y e r c o v e r a g e on t h e s u l p h i d e m i n e r a l s (assuming t h a t each TGA r a d i c a l o c c u p i e s 2 x 1 0 " 1 9 t o 6 x 1 0 " 1 9 m2 of s u r f a c e s i t e ) . The a d s o r b e d s p e c i e s a r e a m i x t u r e of m e t a l t h i o g l y c o l l a t e i n the form of MSCH 2COO _ and HSCH2COOM, t h i o g l y c o l l i c and d i t h i o d i g l y c o l l i c a c i d s . E t h y l x a n t h a t e can a d s o r b on T G A - t r e a t e d s u l p h i d e m i n e r a l s u r f a c e s and on m e t a l t h i o g l y c o l l a t e p r e c i p i t a t e s by d i s p l a c i n g MeOOC- groups a r o u n d n e u t r a l pH. The d e p r e s s i v e a c t i o n of t h i o g l y c o l l i c a c i d i s n o t r e d u c e d by t h e p r e s e n c e of oxygen. I n f a c t , oxygen h e l p s the p r e c i p i t a t i o n of t h i o g l y c o l l i c a c i d o n t o m i n e r a l s u r f a c e i n t h e form of d i t h i o d i g l y c o l l i c a c i d , i m p r o v i n g t h e d e p r e s s i o n . The d e p r e s s i v e a c t i o n of t h i o g l y c o l l i c a c i d r e s e m b l e s t h a t of h y d r o s u l p h i d e , w h i c h i s a d e p r e s s a n t f o r a l m o s t a l l s u l p h i d e s . S e l e c t i v e s e p a r a t i o n of s u l p h i d e m i n e r a l s by TGA a l o n e i s t h e n r a t h e r d i f f i c u l t , a t l e a s t under the c o n d i t i o n s u s e d i n t h i s s t u d y . T h i s r e a g e n t can be a good s u b s t i t u t e f o r c y a n i d e and sodium s u l p h i d e o n l y i n some c i r c u m s t a n c e s . 107 REFERENCE 1. G i b b s , H.L., " D i f f e r e n t i a l f r o t h f l o t a t i o n of s u l p h i d e o r e s " U.S. P a t e n t , 2,449,984 Sep. 1948 2. H i l l , B. "Moly s e p a r a t i o n a t Bagdad and t h e use of ammonium t h i o g l y c o l l a t e " VW & R A p r . 1980 3. Raghavan, S.; Unger, K., " I n t e r a c t i o n of t h i o g l y c o l l i c a c i d w i t h c h a l c o c i t e " T r a n s . IMM 92 June 1983 4. A g a r , G.E., "Copper s u l p h i d e d e p r e s s i o n w i t h t h i o g l y c o l l a t e o r t r i t h i o c a r b o n a t e " CIM B u l l t n . Dec. 1984, 43-46 5. Anon, " S u l p h i d e & n o n s u l p h i d e f l o t a t i o n a p p l i c a t i o n s " M i n . Eng. 34(4) Apr. 1982 377-381 6. C a s t r o , S., " S e l e c t i v e f l o t a t i o n of m o l y b d e n i t e : d e p r e s s i o n mechanisms of c h a l c o c i t e w i t h sodium s u l p h i d e , Anamol-D and Nokes r e a g e n t " P r o c . 13th IMPC. P o l a n d , 1979 181-199 7. N a g a r a j , D.R.; Wang, S.S.; A v o t i n s , D.V., "Copper d e p r e s s a n t s : c o r r e l a t i o n between s t r u c t u r e and a c t i v i t y " P r e p r . M e e t . o f t h e S o u t h e r n Hemisphere on M i n e r a l  T e c h n o l o g y 1982 8. S u t h e r l a n d , K.L.; Wark, I.W., P r i n c i p l e s of f l o t a t i o n , 1955, A u s t r . IMM ( I n c . ) 9. P o l i n g , G.W.; B e a t t i e , M.J.V., " S e l e c t i v e d e p r e s s i o n i n complex s u l p h i d e f l o t a t i o n " P r i n c i p l e s of M i n e r a l  F l o t a t i o n J o n e s , M.H.; Woodcock, J . T . ( e d s . ) , Austr.IMM, 1984 137-146 10. Woods,R., " E l e c t r o c h e m i s t r y of s u l p h i d e f l o t a t i o n " F l o t a t i o n , F u e r s t e n a u , M.C.(ed.) 1976 298-333 11. J a n e t s k i , J.R.; Woodburn, S . I . ; Woods, R., "An e l e c t r o c h e m i c a l i n v e s t i g a t i o n of p y r i t e f l o t a t i o n and d e p r e s s i o n " I n t . J . M i n e r . P r o c . 4,1977, 227-239 12. Agar,G.E.; Kipkie,W.B.; W e l l s , P . F . , "The s e p a r a t i o n of c h a l c o p y r i t e and p e n t l a n d i t e from I n c o M e t a l ' s Sudbury a r e a o r e s " P r o c . 1 4 t h IMPC T o r o n t o , Canada, 1982 13. W e i s s , G., Harzadous c h e m i c a l s handbook, Noyes Data C o r p o r a t i o n ( n d c ) , 1980 ~~ 108 14. T o x i c & h a r z a d o u s i n d u s t r i a l c h e m i c a l s a f e t y manual, I n t . T e c h . I n f o r . I n s t . ( e d . ) , 1976 15. P o d o b n i k , D.M.; S h i r e l e y , J . F . , " M o l y b d e n i t e r e c o v e r y a t C u a j o n e " M i n . Eng. 3 4 ( 1 0 ) , 1982 16. R e d f e a r n , M.A., "The r o l e of n i t r o g e n i n t h e f l o t a t i o n of b y - p r o d u c t m o l y b d e n i t e a t G i b r a l t a r M i n e s " Prepr.AIME  A n n u a l Meet. 83-64, 1983 17. Kauder, O.S., " T h i o g l y c o l l i c a c i d " E n c y c l o p e d i a of  C h e m i c a l T e c h n o l o g y , 3 r d ed., John W i l e y & Sons, 1983, V o l . 2 2 933-946 18. H a r r i s , P . J . ; F i n k e l s t e i n , N.P., "The use of a c l o s e d r e c i r c u l a t i o n a p p a r a t u s i n the s t u d y of t h e g a l e n a - o x y g e n - x a n t h a t e system" NIM R e p o r t No. 1414, J a n , 1973 19. F u e r s t e n a u , D.W.; M e t z g e r , P.H.; S e a l , G.H., "How t o use t h i s m o d i f i e d H a l l i m o n d Tube f o r b e t t e r f l o t a t i o n t e s t i n g " E & MJ 158, 1957 20. P a r t r i d g e , A.C.; S m i t h , G.W., " S m a l l s c a l e f l o t a t i o n t e s t i n g : a new c e l l " T r a n s . IMM 80 Sep. 1971, C119-C120 21. L i g h t , T.S., " S t a n d a r d s o l u t i o n f o r redox p o t e n t i a l measurements" A n a l . Chem. 44, 1972, 1038-9 22. W a l k e r , G.T., "Assay of t h i o g l y c o l l i c a c i d " MFG. Chem. 24, 1953 376-8 23. Day, R.A.; Underwood, A.L., Q u a n t i t a t i v e a n a l y s i s 4 t h ed. P r e n t i c e - H a l l I n c . , New J e r s e y , 1980 285-292 24. K e n d a l l , D . N . ( e d . ) , A p p l i e d i n f r a r e d s p e c t r o s c o p y R e i n h o l d P u b l i s h i n g Co., N.Y., 1966 145-148 25. H a r r i s , D . C . Q u a n t i t a t i v e c h e m i c a l a n a l y s i s , W.H. Freeman & Company, San F r a n . 225-231 26. P o u r b a i x , M , A t l a s of E l e c t r o c h e m i c a l E q u i l i b r i a i n  Aqueous S o l u t i o n s , t r a n s l a t e d by J . A . F r a n k l i n , Pergamon P r e s s , 1966, p388 and p489 27. S a r a s w a t h i , N.; S o u n d a r a r a j a n , S., "Charge d i s t r i b u t i o n , d i p o l e moments and i n f r a r e d s p e c t r a of some t h i o l and t h i o a c i d s " J . M o l . S t r u c t u r e 4, 1969 419-433 28. B e l l a m y , L . J . , The i n f r a r e d s p e c t r a of complex  m o l e c u l e s , Methuen & Co L t d . London, 1958, 2nd ed. 161-176 P o l i n g , G . W.,Infrared s p e c t r o s c o p y of x a n t h a t e compounds  i n t h e s o l i d , s o l u t i o n and a d s o r b e d s t a t e s , M.Sc. T h e s i s , 1961, U n i v . A l b e r t a , Edmonton, Canada K a g a r i s e , R . E . , " S p e c t r o s c o p i c S t u d i e s of the Soaps of P h e n y l s t e a r i c A c i d : I . I n f r a r e d A b s o r p t i o n S p e c t r a and t h e H y d r o l y s i s of Soap F i l m s " , J.Phys.Chem. 59, 1955, 271-277 L e j a , J . , S u r f a c e C h e m i s t r y of F r o t h F l o t a t i o n Plenum P r e s s , 1982, p66 APPENDIX I Kodak I r t r a n I I M a t e r i a l P R O D U C T I O N O F KODAK IRTRAN M A T E R I A L S IKTKAN Mater ia ls are c lassed as hot-pressed polycrysta l-l inu compac t s . E ach is m a d e f r om we l l -known pure inor -gan ic c l i umica l c o m p o u n d s : IKTKAN 1 Mater ia l is m a g -n e s i u m f luo r ide (Mgl-2) a n d IKTKAN 2 Mater ia l is z i n c su l f i de (ZnS) . Each c o m p o u n d of IKTKAN Mater ia l s is re f ined to a pure p o w d e r state pr ior to hot-press ing into a n opt i ca l b l ank . Pur i ty is equal to, or better than , the s a m e mater ia l o f a C P ( chemica l l y pure) grade. Kach IKTKAN Mate r i a l starts i n a fa i r ly conven t i ona l r o u n d m o l d where the temperature is ra ised b y i n d u c t i v e heat ing a n d extreme pressure is a p p l i e d t h r o u g h means of a h y d r a u l i c press. A s chema t i c of the m o l d a n d press ing ar rangement is s h o w n in F i gu re S. K n o u g h p o w d e r is l oaded in each m o l d to fo rm a f ina l dens i f i ed b l ank of what is ca l l ed " o p t i c a l d e n s i t y . " T h e p o w d e r or " c h a r g e " is never hea led h i g h e n o u g h to melt to a truly f l u i d mass. P last ic de fo rmat ion is c o n s i d e r e d the p r imary m e c h a n i s m of dens i f i ca t ion . F i n a l dens i t y is ex-tremely c lose to theoret ical dens i ty . T h e r e is n o e v i d e n c e of any measurab le poros i ty . W h i l e the mass is c o m p o s e d of m a n y t iny c rys ta l l ine aggregates, each gra in face is so c lose l y p a c k e d against adjacent g ra in faces that opt i ca l traitsmittance is poss ib le . H o w e v e r , this gra in " n e s t i n g " duns not b e c o m e 1(1(1 percent comp le t e , a c c o u n t i n g for the v isua l scatter ing ev ident in IKTKAN Mater ia ls . K x u i u p l i s a n d c o m p a r i s o n s of v i sua l transmittancc/scatter ing c an be noted i n F i gu re 6. Fur ther reference to scatter ing a l so c an be noted o n page 1 (>. T h e c o m b i n e d requ i rements of a con ta inment m o l d a n d h igh m o l d i n g pressures l e n d In de f i ne the m a x i m u m s izes that c an be offered read i ly a n d e c o n o m i c a l l y in tin HAN Mater ia ls . A v a i l a b l e s izes of c i r cu l a r b l a n k s a n d spher i ca l d o m e s or caps are tabulated in T a b l e 1. Mos t IKTKAN Mater ia l s emerge f rom the presses a n d m o l d s as c i r cu l a r flat b lanks . T h e first test to de te rm ine b lank qua l i t y is a I ransmit tance lest w h i c h must be m a d e th rough bu f f ed spots o n each face of the b lank . Af ter a b l ank meets w i th in i t ia l a ccep tance , it is then sent to ou r opt i ca l s h o p for s l i c i n g . Mure, r ough wafers larger than l isted s tock th icknesses are cut f r om the entiro b lank d i -ameter a n d are then g r o u n d a n d face-pol ishod to w i t h i n tolerances es tab l i shed for each s tandard th ickness . A t this po in t , a c o m p l e t e I ransmittance check can be made of each s l i ce , after w h i c h it is m o v e d to our stock she lves . Po l i shed w i n d o w s in m a n y s izes are eventua l l y p r o d u c e d Ram Mold Figure 5 Thickness 2 mm 6 mm ILAKITV OF CUOTLNTIO'.M. r«i isi j u m . i u MC IUCRA ~ HAILRIALS. WHICH CANnOt » IN THE VISIBLE SPlCt l EN. nut SO WITH i m u ; VJU. t i l l PRIME SUITAll. IRTRAN 1 Material 2 mm 6 mm H A R l T r OF CONVENTION •:AII Of JUDGED M O O C R A I MATERIALS, WHICH CAW. . wftHU.% uiU- IN THE VISIBLE SPECTI ' LBriKIW A T TICK. NOT SO WITH INFRJ .0 Si r«EHI I C W H S . THE PRIME SUIIABi IRTRAN 2 Material Figure 6 R a f r a c t l v a I n d i e s * K O D A K I n f r a r e d O p t i c a l M a t e r i a l s W i o b t n g t X In Mlcramatraa IRTMN 1 IRTK/M 3 10000 1.3778 2.2907 1.2500 1.3763 2.2777 t 5000 1.3749 2.2706 1.7500 1.3735 2.2662 2.0000 1.3720 2.2631 2.2500 1.3702 2.2608 2.5000 1.3683 2.2569 2.7500 1.3663 2.2573 3.0000 1.3640 2.2558 3.2500 1.3814 2.2544 3 5000 1.3587 2.2531 3.7500 1.3558 2.2518 4.0000 1.3526 2.2504 4.2500 1.3492 2.2491 4.5000 1.34SS 2.2477 4.7500 1.3416 2.2462 5.0000 1.3374 2.2447 5.2500 1.3329 2.2432 5.5000 1 3282 2.2416 5.7500 1.3232 2.2399 6.0000 1.3179 2.2381 6.2500 1.3122 2.2363 6 5000 1.3063 2.2344 6.7500 1.3000 2.2324 7.0000 1.2934 2.2304 7.2500 1.2865 2.2282 7.5000 1.2792 2.2260 7.7500 1.2715 2.2237 8.0000 1.2634 2.2213 8.2500 1.2549 2.2188 8.5000 1.2460 2.2162 8.7500 1.2367 2.2135 9.0000 1.2269 2.2107 9 2500 2.2078 9.5000 2.2048 9.7500 2.2018 10.0000 2.1988 11.0000 2.1846 12.0000 2.1688 13.0000 2.1508 Index of refraction values were experimentally determined it selected wavelengths between 1 and 10 p. Coefficients of en Interpolation formula were established and reduced by least squares methods, and In* values computed. Alt values beyond 10 M are extrapolated. Table I n d i c e s of R e f r a c t i o n for I R T R A N M a t e r i a l s B a s e I n d e x a n d C o e f f i c i e n t s C M I M W I U I f t TM* 1 Malarial tKTOAH 2 Malarial n„ 1.3776955 b 1.3515529 x 10* c 2.1254394 x 1&« d -1.5041172 x 10* a -4.4109708 x 10* 2.2569735 3.2640935 x 10* 8.0314637 x 10"« -5.2705532 X 10"4 -6.0428638 x I C ' Tab la A3 1 8 S ° 33NVI1IV«NV»I 1N139M APPENDIX I I C o n d i t i o n s of I o d i n e t i t r a t i o n of. TGA I o d i n e t i t r a t i o n of TGA i s an o x i d a t i o n p r o c e s s , so o n l y the u n o x i d i z e d s p e c i e s a r e d e t e r m i n e d . To d e t e r m i n e t h e c o n c e n t r a t i o n of TGA w i t h o x i d i z e d p r o d u c t , DTGA, t h e s o l u t i o n i s f i r s t r e d u c e d w i t h z i n c m e t a l t h e n t i t r a t e d w i t h i o d i n e . 1. D e t e r m i n a t i o n of r e d u c t i o n t i m e w i t h Zn To d e t e r m i n e t h e r e d u c t i o n time o f TGA s o l u t i o n s w i t h z i n c m e t a l , an o x i d i z e d TGA s o l u t i o n was p r e p a r e d by r e a c t i n g 4 grams of -150# c h a l c o p y r i t e w i t h 400 ml 0.001M TGA, f i l t e r i n g t h e s o l u t i o n and l e a v i n g i t open t o a i r o v e r n i g h t . The n e x t day, t h e pH v a l u e of t h e s o l u t i o n was a d j u s t e d t o 1, z i n c m e t a l was added and t h e s o l u t i o n was s t i r r e d f o r a c e r t a i n t i m e . A f t e r f i l t r a t i o n and washing w i t h HC1 s o l u t i o n (pH=1), t h e f i l t r a t e was t i t r a t e d w i t h 0.006N i o d i n e . The r e s u l t s a r e shown i n F i g . A2 . I t i s seen t h a t a r e d u c t i o n t i m e of 5 min. i s enough t o re d u c e a l l t h e DTGA. I t i s a l s o n o t e d t h a t the amount of i o d i n e consumed i s more t h a n t h e e q u i v a l e n t amount. T h i s was c o n s i d e r e d t o be the e f f e c t of t h e pH v a l u e a t which t h e t i t r a t i o n was c o n d u c t e d . N e x t , t h e e f f e c t of pH on t h e t i t r a t i o n was t e s t e d . 3 o —• o o 2 o / 1 pH 1 ( 0 ) 1 1 1 1 1 1 1 1 1. 1 1 i i i i • 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 Reaction Time with Zinc, min. Fig.A2 Reduction of T h i o g l y c o l l i c Acid with Zinc Metal and Corresponding Iodine Consumption 0.006 N I 2 / 10 ml 10~3M TGA D e t e r m i n a t i o n of t i t r a t i o n pH A s t o c k e d TGA s o l u t i o n was d i r e c t l y t i t r a t e d w i t h 0. 005N i o d i n e a t d i f f e r e n t pH v a l u e s . R e s u l t s a r e shown i n F i g . A3. I t i s seen t h a t o n l y i n t h e pH range of 3 t o 9 i s t h e t i t r a t i o n r e s u l t c o r r e c t . S i n c e , a t pH above 3, t h e r e d u c t i o n of TGA by Zn was found t o be i n e f f e c t i v e , the t i t r a t i o n p r o c e d u r e was d e t e r m i n e d t o be t h e Z n - r e d u c t i o n of t h e s o l u t i o n a t pH 1, f o l l o w e d by t h e t i t r a t i o n of t h e s o l u t i o n a t pH Ol \ o J equivalent volume Q 1 1 1 1 1 i i i 1 1 1 1 1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 pll Fig.A3 E f f e c t of pH Value of TGA Solution on Iodine T i t r a t i o n 0.005 N I 0 / 10 ml 10~3M TGA (18 APPENDIX I I I P o u r b a i x Diagrams of t h e Copper-Water  System and t h e Lead-Water System 119 F i g . M Potential-pH Diagram of the Water-Copper System [26] F i g . A5 Potential-pH Diagram of the Water-Lead System [26] 

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