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The surface reactions between flotation re-agents and minerals. The action of cyanide in the flotation… Fitch, Fred Troop 1940

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THE SURFACE REACTIONS BETlfEEN FLOTATION REAGENTS AND MINERALS THE ACTION Off CYANIDE IN THE FLOTATION OF SPHALERITE  by  F. T. F i t c h  A T h e s i s submitted f o r the Degree of MASTER OF ARTS i n the Department of  '  CHEMISTRY  A p r i l , 1940  ACKNOWLEDGEMENT I s h o u l d ' l i k e t o take t h i s  opportunity  t o express my thanks t o Dr. W i l l i a m TJre, under whose s u p e r v i s i o n t h i s work was und e r t a k e n , f o r h i s u n f a i l i n g i n t e r e s t and many h e l p f u l s u g g e s t i o n s .  CONTENTS Page I.  P r e l i m i n a r y Survey • flotation  II.  1  F r o t h i n g Agents  2  C o l l e c t i n g Agents  4  A c t i v a t i o n , D e a c t i v a t i o n , D e p r e s s i n g Agents  5  Flotation of Sphalerite  7  Objects o f Present Work  13  E x p e r i m e n t a l Work Methods of A n a l y s i s  III.  CN" D e t e r m i n a t i o n  14  Zinc Determination  15  Santhate D e t e r m i n a t i o n  16  F l o t a t i o n T e s t s and R e s u l t s  18  A c t i v a t i o n and D e a c t i v a t i o n  24  Xanthate A b s t r a c t i o n T e s t s  26  Cyanide A b s t r a c t i o n T e s t s  27  Summary o f R e s u l t s  32  References  34  PRELIMINARY SURVEY FLOTATION F l o t a t i o n i s a method of ore c o n c e n t r a t i o n dependent upon the tendency o f a c o n s t i t u e n t o r c o n s t i t u e n t s o f a f i n e l y ground m i n e r a l t o c o l l e c t a t an a i r - w a t e r i n t e r f a c e ^  I t con-  s i s t s o f i n t r o d u c i n g a q u a n t i t y o f gas bubbles i n t o a pulp o f ore and water, and o b t a i n i n g t h e v a l u a b l e p o r t i o n i n t h e r e sultant froth.  As t h e bubbles r i s e , they come i n contact w i t h  the m i n e r a l p a r t i c l e s , and t h e d e s i r e d c o n s t i t u e n t s , a t t a c h e d t o the bubbles, are c a r r i e d upward.  That m i n e r a l which c o l -  l e c t s a t the i n t e r f a c e / i s known as the " c o n c e n t r a t e s " because o f i t s h i g h content o f v a l u a b l e substances,  w h i l e that  p o r t i o n which d i d not c o l l e c t t h e r e , but s e t t l e d t o t h e bottom i s c a l l e d t h e " t a i l i n g s " * and i s u s u a l l y d i s c a r d e d .  The f r o t h  i s a l l o w e d t o o v e r f l o w and c a r r i e s with i t the c o n c e n t r a t e s . I n order to make t h i s process p o s s i b l e i n i t s present  form,  a number o f f l o t a t i o n agents must be added p r i o r t o and d u r i n g flotation» c o n t r o l of these reagents b e i n g p r o b a b l y t h e most important f a c t o r i n t h e o p e r a t i o n .  Without these reagents t h e  m i l l operator would have t o depend on o n l y a s l i g h t f r o t h t o keep the m i n e r a l a t t h e s u r f a c e , and on the r e l a t i v e n a t u r a l f l o a t a b i l i t i e s o f the c o n s t i t u e n t s t o achieve h i s s e p a r a t i o n s * With o n l y these t o r e l y on, t h e present  day .operation of many  p l a n t s would not be e c o n o m i c a l l y p o s s i b l e or p r a c t i c a l . F l o t a t i o n depends upon t h e a b i l i t y o f the; a i r t o d i s p l a c e  2 .water from the p a r t i c l e s u r f a c e .  Thus the s u r f a c e must be or  i g i n a l l y hydrophobic o r , as i n most cases, rendered so by treatment -with the c o l l e c t o r .  The  'contact a n g l e , formed by  the air-^water and water s o l i d i n t e r f a c e s i s considered t o be "an i n d i c a t i o n of the: tendency of a gas t o d i s p l a c e water from c o n t a c t - w i t h the m i n e r a l .  T  1 < }  .  Solid  F l o t a t i o n has been s t u d i e d by means of the contact by Wark ,.and Cox  ( 2 ) , and numerous other i n v e s t i g a t o r s .  angle Its  presence has been used e x t e n s i v e l y to show f l o t a t i o n p o s s i b l e without  the. a c t u a l f l o t a t i o n operation,, and a l s o t o g i v e  i n d i c a t i o n of the c o n d i t i o n o f the m i n e r a l  an  surface.  FLOTATION REAGENTS F l o t a t i o n agents have many f u n c t i o n s .  C h i e f l y they have  to do w i t h the f o r m a t i o n of a f r o t h , or w i t h m o d i f i c a t i o n s of the f l o a t a b i l i t y of the m i n e r a l , whether by a c t i o n on the  min  e r a l i t s e l f or by c o n t r o l l i n g the c o n d i t i o n s d u r i n g the operation.  An i d e a o f the many f u n c t i o n s of these reagents may  b  obtained by a glance at the names of the v a r i o u s groups, such as; f r o t h i n g a g e n t s , c o l l e c t i n g agents, a c t i v a t i n g , d e a c t i v a t i n g and d e p r e s s i n g  agents, pH r e g u l a t o r s , c l e a n s i n g a g e n t s ,  3 and f i n a l l y . d i s p e r s i n g agents.  I n a d d i t i o n , these reagents  may  have more than one f u n c t i o n a t the same time f o r a m i n e r a l , or may have d i f f e r e n t f u n c t i o n s f o r d i f f e r e n t o r e s .  I t i s by  t a k i n g advantage of the p r o p e r t i e s of these f l o t a t i o n agents t h a t the p r e s e n t day m i l l o p e r a t i o n s are c a r r i e d on. :'FROTHING i 5 W S For e f f i c i e n t , f l o t a t i o n , a f r o t h on the s u r f a c e i s nece s s a r y to r e t a i n the m i n e r a l brought up by the bubbles.  This  i s obtained by the a d d i t i o n of a v e r y s m a l l amount of f r o t h i n g agent, o r d i n a r i l y l e s s than one pound per ton o f o r e .  Froth-  i n g agents are u s u a l l y o r g a n i c compounds which lower the s u r face t e n s i o n of the s o l u t i o n , sometimes c o n s i d e r a b l y d e s p i t e v e r y s m a l l c o n c e n t r a t i o n s , and thus i n accordance w i t h Gibb's a d s o r p t i o n e q u a t i o n tend t o c o n c e n t r a t e at the a i r - w a t e r i n terface.  Most o f these reagents have s t r u c t u r a l formulas  c h a r a c t e r i z e d by the presence o f two c o n s t i t u e n t s of o p p o s i t e p r o p e r t i e s i n the m o l e c u l e , t h a t i s each have a p o l a r and a non-polar p o r t i o n ; and as a r e s u l t tend t o arrange  themselves  at an i n t e r f a c e so that the p o l a r end i s a t t a c h e d to the water and the n o n - p o l a r away from the water.  T h e r e f o r e the bubbles  t e n d to come i n t o c o n t a c t w i t h each o t h e r w i t h o u t c o a l e s c i n g due t o t h e p r o t e c t i v e sheath of f r o t h e r molecules at the i n t e r f a c e , and form a f r o t h i n s t e a d of b r e a k i n g when',,-they r e a c h the surface.  I n the s e l e c t i o n o f a f r o t h i n g agent, c o s t , a v a i l -  a b i l i t y , and l a c k o f c o l l e c t i n g p r o p e r t i e s , s i n c e they would l i m i t reagent c o n t r o l are sought.  I n a c t u a l p r a c t i c e today,  probably, the most w i d e l y used f r o t h e r s are p i n e o i l and  cres-  4 ylic  acid.  COLLECTING- AGENTS C o l l e c t i n g agent i s the term used t o d e s c r i b e those chemi c a l s necessary  i n most cases t o b r i n g the d e s i r e d m i n e r a l i n -  to the f r o t h i n a p p r e c i a b l e q u a n t i t i e s .  I t was f i r s t used t o  a p p l y t o t h e c o l l e c t i n g o i l s i n o i l f l o t a t i o n j and I s s t i l l retrained "although the a c t i o n o f the modern c o l l e c t i n g a g e n t - i s a p p a r e n t l y very d i f f e r e n t t o the no l o n g e r used c o l l e c t i n g oils.  C o l l e c t o r s form a non^polar  water r e p e l l e n t c o a t i n g on  the s u r f a c e of c e r t a i n m i n e r a l p a r t i c l e s j e i t h e r by adsorp-^ t i o n or by chemical r e a c t i o n w i t h the s u r f a c e .  This  enables  the m i n e r a l t o a t t a c h i t s e l f t o the gas bubble r e a d i l y .  Since  the e f f e c t of c o l l e c t i n g agents v a r y w i t h the d i f f e r e n t mine r a l s , the c o n s t i t u e n t s can be separated from each o t h e r , a process known as s e l e c t i v e f l o t a t i o n *  I n some cases the c o l -  l e c t o r s have been shown t o form d e f i n i t e compounds by metat h e s i s a t the s u r f a c e * f o r example, galena and the xanthates ( 3 j ( f ) ) w h i l e i n other cases t h e c o l l e c t o r i s known t o be r e moved from s o l u t i o n j although the mechanism f o r t h i s i s not clear.  L i k e f r o t h e r m o l e c u l e s , t h e c o l l e c t o r molecules are  composed of two p a r t s * p o l a r and non«polar, and are capable of r e a c t i n g o r adsorbing'on  the m i n e r a l .  There are' a g r e a t v a r -  i e t y of c o l l e c t o r s i n use at the present time j o r g a n i c compounds of n i t r o g e n and s u l p h u r b e i n g used m o s t l y f o r the meta l l i c sulphides.  The use of xanthate w i t h m e t a l s u l p h i d e s ,  p a r t i c u l a r l y i n r e g a r d to s p h a l e r i t e w i l l be d i s c u s s e d  later.  5 ACTIVATING-,) DEACTIVATING AND  DEPRESSING/AGENTS  Many chemicals through t h e i r e f f e c t upon the s u r f a c e of the m i n e r a l change the f l o a t a b l e p r o p e r t i e s o f the ore w i t h the u s u a l c o l l e c t o r s .  These chemicals* known as a c t i v a t i n g *  d e a c t i v a t i n g , and d e p r e s s i n g agents a r e w i d e l y used i n the present day s e l e c t i v e f l o t a t i o n processes t o f u r t h e r m o d i f y the f l o a t a b i l i t y o f the v a r i o u s c o n s t i t u e n t s .  Perhaps the  best known examples o f these are the a c t i v a t i o n o f s p h a l e r i t e by copper s u l p h a t e , the d e a c t i v a t i n g e f f e c t of potassium cyanide on s p h a l e r i t e , and the d e p r e s s i n g e f f e c t o f potassium chromate on p a r t l y o x i d i z e d g a l e n a ; A c t i v a t i n g agents a r e used to make p o o r l y f l o a t a b l e mine r a l s more amenable to f l o t a t i o n under the u s u a l c o n d i t i o n s * T h e i r e f f e c t i s due to t h e i r a c t i o n on the s u r f a c e , namely forming a compound more' i n s o l u b l e than those o f the m e t a l  com-  pounds a l r e a d y t h e r e , but which i s s t i l l a b l e t o r e a c t r e a d i l y w i t h the c o l l e c t o r t o form.a l e s s s o l u b l e s u r f a c e s a l t would be n o r m a l l y formed.  Supporters  o f the chemical  than theory  go so f a r as t o s a y . t h a t w i t h a complete t a b l e o f water s o l u b i l i t i e s , one should be able t o p i c k an a c t i v a t o r f o r a mine r a l even b e f o r e t r i a l *  Thus s a l t s o f mercury, copper, and  1  l e a d , whose s u l p h i d e s and o r g a n i c s a l t s are g e n e r a l l y more i n s o l u b l e than those o f o t h e r m e t a l s , o f t e n prove t o be the best activators.  Chemicals t h a t undo the work o f a c t i v a t o r s are  known as d e a c t i v a t i n g agents.  They a r e srery important i n floa-  t a t i o n , b e i n g r e q u i r e d to overcome the n a t u r a l l y o c c u r i n g a c t i v a t i o n among t h e m i n e r a l s , such as the a c t i o n of copper s a l t s  i n complex .copper z i n c o r e s . Other r e a g e n t s , known as d e p r e s s i n g agents, are used to decrease the f l o a t a b i l i t y of c e r t a i n r e a d i l y f l o a t a b l e cons t i t u e n t s of the ore.  They form upon the m i n e r a l s u r f a c e a  c o a t i n g much l e s s f l o a t a b l e than the m i n e r a l s u r f a c e i t s e l f . Thus the d i f f e r e n c e  between an a c t i v a t o r and a  depressor  would appear to be t h a t the s u r f a c e compound formed by the l a t t e r i s both p o o r l y f l o a t a b l e and r e s i s t a n t t o w i t h the c o l l e c t o r .  reaction  7 THE FLOTATION OF . SPHALERITE S p h a l e r i t e , the most common ore o f z i n c * i s found associ a t e d w i t h other s u l p h i d e ores o f i r e n * copper, cadmium, and . lead*  I t " ' i s a l i g h t g r a y i s h y e l l o w c o l o u r when pure, but  t r a c e s o f i r o n s u l p h i d e , which i t most commonly c o n t a i n s change the ore to a much darker brown c o l o u r .  'It has a r e s i n -  ous l u s t e r , s p e c i f i c g r a v i t y o f 3.9 t o 4*1, and i s b r i t t l e w i t h a: d e f i n i t e cleavage.  •  S p h a l e r i t e i s one o f t h e most d i f f i c u l t m i n e r a l s t o float*  under c o n d i t i o n s as obtained i n the m i l l c i r c u i t s  i n g the commercial process  dur-  i t i s not recovered u n l e s s s u b j e c t -  ed t o a c t i v a t i o n by added s a l t s due t o presence of other  ores.  Pure s p h a l e r i t e I s o n l y f l o a t e d w i t h i n a narrow pH range, and then o n l y by some c o l l e c t o r s , e s p e c i a l l y those c o n t a i n i n g a carbon c h a i n o f f i v e or more atoms. u t i o n s d e f i n i t e l y prevent  flotation.  B a s i c and a c i d i c  sol-  There seems to be much  d i f f e r e n c e o f o p i n i o n i n the r e p o r t s r e g a r d i n g the f l o t a t i o n o f s p h a l e r i t e • b y the lower x a n t h a t e s .  Yamada and Yaganuma (4)  r e p o r t s 99$ r e c o v e r y f o r pH's o f 5.5 t o 7*5 u s i n g potassium e t h y l x a n t h a t e , w h i l e above t h i s i t drops t o 10$. and  Gaudin (5)  ( 6 ( e ) ) , r e p o r t s p r a c t i c a l l y no r e c o v e r y f o r s p h a l e r i t e o f  100 t o 600 mesh w i t h potassium e t h y l xanthate.  Wark and Gox  (3(a) p.199 and 220/) who used contact angles as an i n d i c a t i o n of f l o a t a b i l i t y r e p o r t t h a t no contact angle i s obtained i n e i t h e r d i s t i l l e d water, or a potassium e t h y l xanthate ion.  solut-  They a l s o s t a t e t h a t no c o n t a c t angle i s o b t a i n e d f o r  8 amyl and lower xanthates without a c t i v a t i o n .  Experiments  con-  ducted i n t h i s l a b o r a t o r y and t o be d i s c u s s e d l a t e r have shown f l o t a t i o n p o s s i b l e f o r a pH range o f r o u g h l y 4.to 7.5 f o r the u n a c t i v a t e d ore*  I t i s r e p o r t e d from s e v e r a l sources t h a t  s p h a l e r i t e does not a b s t r a c t potassium e t h y l xanthate from s o l u t i o n (5) and (8) and t h a t no l a y e r can be leached from the ore;  w h i l e the a c t i v a t e d ore has been shov/n t o a b s t r a c t xan~ <  t h a t e from s o l u t i o n ( 5 ) .  C.R.  Ince ( 6 ( b ) ) has shown s p h a l e r -  i t e t o remove xanthate from solution'* although not n e a r l y t o the same extent as g a l e n a .  G-alena ((5) p66) has been shown t o  a b s t r a c t xanthate Ion from s o l u t i o n and f u r t h e r the m e t a l xant h a t e so formed has been l e a c h e d from the ore and as such.  identified  While galena••(&(f)) i s p r o b a b l y the o n l y m i n e r a l f o r  which f l o t a t i o n has d e f i n i t e l y been shown to be due to the f o r m a t i o n o f a m e t a l xanthate' surfa'ee compound, removal of xanthate Ion would be expected to accompany f l o t a t i o n , whatever the mechanism i n v o l v e d .  Thus t h i s would i n d i c a t e t h a t  no f l o t a t i o n took p l a c e under the c o n d i t i o n s f o r which the above measurements showed no removal. I n l i n e w i t h the chemical t h e o r y of f l o t a t i o n , i t has been suggested t h a t the s o l u b i l i t y of z i n c e t h y l xanthate was (  . . .  •  .  -  r e s p o n s i b l e f o r some o f the f l o a t a b l e p r o p e r t i e s of s p h a l e r i t e * Z i n c e t h y l xanthate i s more s o l u b l e than most of the other m e t a l x a n t h a t e s , b e i n g r e p o r t e d as 0 . 3 5 5 g / l i t r e (9) and ( 1 0 ) . Thus under c o n d i t i o n s where other m i n e r a l s might f l o a t , t h e r e would be no f l o t a t i o n because the c o n c e n t r a t i o n o f z i n c i o n s . and xanthate i o n s would not be h i g h enough t o cause the form-  9 a t i o n o f a-metal xanthate s u f f i c i e n t xanthate  i o n would be destroyed  p o s i t i o n o f xanthate^ a c i d t o prevent  l a y e r on the s u r f a c e .  For l o w pH's  due t o the decom-  or removed due t o the u n i o n i z e d x a n t h i e  f l o t a t i o n * where as f o r a l k a l i n e r a n g e s , the  c o n c e n t r a t i o n o f z i n c i o n would be kept down enough by t h e f o r m a t i o n of i n s o l u b l e z i n c hydroxide  o r z i n c a t e i o n s t o pre-  vent the f o r m a t i o n Of z i n c e t h y l xanthate  on-the ore s u r f a c e .  The much g r e a t e r pH range through ydiich galena and copper ores f l o a t i s . e x p l a i n e d by the extreme i n s o l u b i l i t y o f t h e i r metal xanthates« D e s p i t e t h e c o n f l i c t i n g r e p o r t s on t h e f l o a t a b i l i t y of s p h a l e r i t e j a l l agree t h a t the pure u n t r e a t e d m i n e r a l w i l l not float i n alkaline solutions.  Thus t o r e c o v e r s p h a l e r i t e i n  the m i l l s where a l k a l i n e c i r c u i t s a r e now almost u n i v e r s a l l y used, i t must be t r e a t e d f i r s t w i t h some s a l t t o a c t i v a t e i t , t h a t i s t o permit i t t o r e a c t w i t h the c o l l e c t o r .  The most  common s a l t f o r t h i s purpose i s copper s u l p h a t e , b u t any copper s a l t has been found t o have p r a c t i c a l l y the same e f f e c t . T h i s i s a t t r i b u t e d t o t h e c u p r i c i o n r e a c t i n g a t the s u r f a c e t o form a l a y e r o f copper s u l p h i d e and r e l e a s i n g the z i n c i o n i n t o t h e s o l u t i o n i n c h e m i c a l l y e q u i v a l e n t amounts (6(d&e))„ i.e.  G\x + Z n S — *  ++  Zn +  CuS.  Most o f t h e work seems t o favour t h e o p i n i o n t h a t the l a y e r so formed i s c u p r i c sulfide» although t h a t i t i s cuprous s u l p h i d e , or a m i x t u r e  others have s t a t e d  o f both ( 9 ) . T h i s  c u p r i c s u l p h i d e i s capable o f o x i d a t i o n and subsequent r e a c t i o n with t h e c o l l e c t o r , thus g i v i n g f l o t a t i o n .  Experiments  10 have been conducted t o see i f cuprous s a l t s mere more e f f i c i ent a c t i v a t o r s , but have shown t h a t f o r e q u i v a l e n t amount of copper, they have a p p r o x i m a t e l y t h e same e f f e c t  (6(d)).  Other m e t a l i o n s have been shown t o have a s i m i l a r a c t i v a t i n g e f f e c t on s p h a l e r i t e . .  I n g e n e r a l , those s a l t s forming  s u l p h i d e s l e s s s o l u b l e than z i n c s u l p h i d e have been found e f f e c t i v e . (11 ) . Most o f these metals a l s o form xanthates much more i n s o l u b l e than z i n c e t h y l x a n t h a t e , thus e x p l a i n i n g such a sulphide, l a y e r should g i v e f l o t a t i o n *  why  R a l s t o n and  Hunter have s t a t e d t h a t the l e a d i o n shows no a c t i v a t i n g e f f e c t on s p h a l e r i t e , but o t h e r s have found d e f i n i t e a c t i v a t i o n by t h i s i o n . They a l s q examined the a c t i v a t i n g e f f e c t o f the m e t a l i o n s f o r percentage z i n c i n the concentrates.and a l s o percentage z i n c e x t r a c t e d ,  results*  reporting . ,  copper t o g i v e the best (15),  R a v i t z and W a l l (12>) and o t h e r s \ 1 4 ) g i v e A  additional  i n f o r m a t i o n about the e f f e c t o f copper s u l p h a t e on s p h a l e r i t e . In actual practice  copper, s u l p h a t e i s added t o the p u l p ,  p r e c i p i t a t e d as h y d r o x i d e , carbonate, o r b a s i c carbonate, which then a l l o w s s u f f i c i e n t copper i o n c o n c e n t r a t i o n f o r the formation of a surface cupric sulphide l a y e r .  Sphalerite  i s not  n a t u r a l l y f l o a t a b l e i n a l k a l i n e c i r c u i t s , and i s o n l y o b t a i n e d i n the c o n c e n t r a t e s when i t has been a c t i v a t e d by some such s a l t , e i t h e r added f o r t h i s purpose, o r formed by o x i d a t i o n of one o f the c o n s t i t u e n t s  o f the ore*  '  Because o f t h i s n a t u r a l l y o c c u r i n g a c t i v a t i o n o f the s p h a l e r i t e , a means o f d e a c t i v a t i o n flotation.  i s necessary f o r s e l e c t i v e  I t has been found t h a t the a d d i t i o n o f some cyanide  11 s a l t , such, as sodium or potassium cyanide w i l l reduce t h e f l o t a b i l i t y t o t h a t o f the u n a c t i v a t e d ore*  This i s considered  due t o the removal of the c u p r i c s u l p h i d e l a y e r w i t h t h e forma t i o n o f a very s l i g h t l y d i s s o c i a t e d complex cupro*>cyanide ion  GutCM")^*"* ( 6 ( e ) ) .  Cyanide i s a l s o found t o be e f f e c t i v e i n  p r e v e n t i n g the f l o t a t i o n o f many other s u l p h i d e m i n e r a l s  such  as p y r i t e , c o v e l l l t e , and other copper ores» w h i l e i t has no e f f e c t a t a l l on the r e c o v e r y o f galena* In  a d d i t i o n t o t h i s d e a c t i v a t i n g e f f e c t , cyanide i s by ;  many ( 9 ) * ( 1 0 ) , (.15.), ( 1 6 ) , c o n s i d e r e d t o form a h y d r o p h i l i c l a y e r o f i n s o l u b l e and. complex s a l t s on t h e m i n e r a l s u r f a c e * thus f u r t h e r impeding  f l o t a t i o n ; , Del Guidice, i n a d d i t i o n ,  s t a t e s t h a t ore t r e a t e d w i t h ECU does not a b s t r a c t potassium e t h y l xanthate from s o l u t i o n .  On the o t h e r hand, TucKer and  Head (17) found cyanide t o have l i t t l e of s p h a l e r i t e *  •  e f f e c t on the f l o t a t i o n  I n support o f t h i s j Gaudin ( 5 , p77 and 224)  (6 e) r e p o r t s cyanide t o be without e f f e c t upon "the unactivat-r ed o r e , and t o reduce the f l o a t a b i l i t y o f the a c t i v a t e d ore t o t h a t o f the u n t r e a t e d m i n e r a l *  Perhaps the most e x t e n s i v e  work on t h e e f f e c t -of cyanide i n f l o t a t i o n has been done by l a r k 'and Cox (2) (3a, b, c ) (18) who used c o n t a c t angle meas}  urements. ide  They found f o r t h e v a r i o u s m i n e r a l s a , c e r t a i n cyan-  s a l t c o n c e n t r a t i o n f o r each pH which would d e f i n i t e l y p r e -  vent c o n t a c t o f a i r and m i n e r a l .  Further i n v e s t i g a t i o n o f  t h i s data showed t h e cyanide i o n c o n c e n t r a t i o n t o be constant throughout  f o r each m i n e r a l .  These r e s u l t s , d e s p i t e being the  most e x t e n s i v e oh the s u b j e c t , f a i l t o i n d i c a t e t h e mechanism  12 involved..*' C. R. Ince ( 6 ( b ) ) and B r i g h t o n , Burgener, and Gross (12) have showed s m a l l q u a n t i t i e s o f cyanide i o n t o be removed from s o l u t i o n by contact w i t h s p h a l e r i t e . Yet even w i t h a l l t h i s data a v a i l a b l e , the a c t i o n o f cyanide/remains somewhat clouded.  I t s d e a c t i v a t i n g e f f e c t , depending upon  the removal o f CuS, i s r e c o g n i z e d by a l l , w h i l e other t h e o r i e s such as t h e f o r m a t i o n o f a water a v i d l a y e r ; as t h e removal of m e t a l xanthate  l a y e r due t o i n c r e a s e d s o l u b i l i t y i n cyanide  s o l u t i o n and others remain d i s p u t e d .  S p h a l e r i t e i s a l s o de-  pressed by s e v e r a l other s a l t s , such as s o l u b l e s u l p h i t e s ; thiosulphatesand  sodium s u l p h i d e .  F u r t h e r , i t was a l s o shown t h a t washing the ore w i t h a d i l u t e a c i d was such as HgSO^ (5) (19) and HOI (20) p r i o r t o the f l o t a t i o n t e s t s gave much h i g h e r r e c o v e r y .  T h i s was  e x p l a i n e d as a c l e a n s i n g a c t i o n which removed s l i m e c o a t i n g s , and thus a i d e d f l o t a t i o n . f o r :p|?i?£te"iion.  A s i m i l a r e f f e c t was a l s o r e p o r t e d  13  OBJECT OF PRESENT'WORK I n the present day s e l e c t i v e f l o t a t i o n o f s p h a l e r i t e two r e a g e n t s , copper sulphate'and sodium cyanide seem t o p l a y a major p a r t .  -While t h e a c t i o n o f the former i s understood,  t h e r e s t i l l remains c o n s i d e r a b l e the cyanide.  doubt as t o the f u n c t i o n o f  I t has been suggest-ed that cyanide., i n a d d i t i o n  to removing the a c t i v a t i n g f i l m o f c u p r i c s u l p h i d e  on the min-  e r a l s u r f a c e , a l s o may form a h y d r o p h i l i c l a y e r i t s e l f , o r may d i s s o l v e the m e t a l xanthate l a y e r . was  I n the p r e s e n t work i t  hoped t o f u r t h e r c l a r i f y t h i s , and, i f p o s s i b l e , t o de-  termine whether the cyanide's o n l y e f f e c t was t h a t o f deactivation.  F o r t h i s , copper f r e e samples o f s p h a l e r i t e were  used, and a l s o , as i n p r e v i o u s i n v e s t i g a t i o n s i n t h i s lab-* o r a t o r y , potassium e t h y l xanthate and t e r p i n e o i were s e l e c t e d as a t y p i c a l c o l l e c t o r and f r o t h e r ,  ..'._ .  14  EXPERIMENTAL WORK METHODS. OF ANALYSIS Cyanide, D e t e r m i n a t i o n The methods suggested  i n the l e t e r a t u r e were of two  t y p e s , namely b y : t i t r a t i o n , e i t h e r p o t e n t i o m e t r i c * or u s i n g EClas  an i n d i c a t o r , or by c o l o r i m e t r i c determination*.  The  p o t e n t i o m e t r i c a n a l y s i s (21) was d i s c a r d e d when i t was found t h a t an u n s a t i s f a c t o r y end-point concentrations.  was obtained a t the d e s i r e d  Two c o l o r i m e t r i c methods, the f i r s t depend*  i n g on the f o r m a t i o n of r e d F e ( C N S )  3  (22) and the second de-  pending upon the f o r m a t i o n of p r u s s i a n blue (23) was d i s c a r d ed as u n s a t i s f a c t o r y before a s u i t a b l e t e s t was,found.  The  former gave very low r e s u l t s , w h i l e the l a t t e r was n o t s e n s i t i v e enough,; f a i l i n g t o i n d i c a t e the presence o f GN i n a s o l u t i o n o f 1 p a r t NaCN i n 50,000 p a r t s water* However a method r e p o r t e d by R. G-. Smith (24) proved t o be v e r y s e n s i t i v e and convenient*  T h i s d e t e r m i n a t i o n depended  on the c o l o r a t i o n on h e a t i n g o f an a l k a l i n e s o l u t i o n of s a t u r a t e d p i c r i c a c i d i n the presence o f c y a n i d e , due to the f o r mation of a sodium s a l t o f i s o p u r p u r i c a c i d .  For t h i s work, a  standard c o l o r i m e t e r machine, No 7-089 F i s h e r E l e c t r o - p h o t o meter, was a v a i l a b l e . d i f f e r e n t cyanide  T e s t s were conducted on a s e r i e s o f  s o l u t i o n s , and the machine r e a d i n g s p l o t t e d  against concentration.  The r e s u l t i n g values were found t o  f a l l on a s t r a i g h t l i n e , the slope o f which v a r i e d s l i g h t l y  i  _  i  1 i 1 1  • J .  -——,—^-^™—|—:  - |  j \  i \  \'  — • :\ 7  \ - -  I \  -  -  —;—'— ; •  -  , .....  Q  ©  s  -a c  id  c o  id a -  —a —aj if  a-  *.2  °i s -OJ-S-  4 p  *  15 from .day t o day,"apparently  depending on how e x t e r n a l c o n d i t - '  i o n s a f f e c t e d the s e n s i t i v i t y of t h e c o l o r i m e t e r . adopted was t o prepare standard  The method  s o l u t i o n s of n e a r l y . t h e same  . c o n c e n t r a t i o n as the unknown, and then compare readings> all determinations  being made at the same time*  The procedure;as d e s c r i b e d i n the l i t e r a t u r e was m o d i f i e d to i n c r e a s e i t s s e n s i t i v i t y , in. the f o l l o w i n g manner:-The c o l oured sample was. prepared  by h e a t i n g Sec's o f unknown oyanide  s o l u t i o n w i t h 3ce's of p i c r i c a c i d s o l u t i o n (3 volumes o f s a t u r a t e d p i c r i c a c i d and 1 volume o f 1,0% N a C 0 2  f i v e minutes on a steam bath.  g  solution) for  The s o l u t i o n was. then immediat-  e l y cooled i n running/Water and d i l u t e d t o 25cc's. R e s u l t s of d e t e r m i n a t i o n s  over c o n c e n t r a t i o n ranges of  0 t o 1.6 p a r t s per 100,000 p a r t s water, and over 1.6 p a r t s p e r 100,000 t o 1 p a r t per 12,500 are shown*  The d i f f e r e n c e i n  s l o p e s of the l i n e s obtained by p l o t t i n g these readings aga i n s t c o n c e n t r a t i o n i s due t o t h e two s e t s o f r v a l u e s being determined  s e p a r a t e l y i n the c o l o r i m e t e r !  more concentrated  The values f o r the  s e r i e s show v e r y l i t t l e d e v i a t i o n from a  s t r a i g h t l i n e . , and i n d i c a t e t h a t c o n c e n t r a t i o n s of from .02 t o *09mg/cc, the range i n which we are i n t e r e s t e d , m a y b e d e t e r mined w i t h much l e s s than 5% e r r o r by the above method, Zinc. A n a l y s i s . Z i n c was determined by p o t e n t i o m e t r i c t i t r a t i o n as desc r i b e d by I . R. Pearce (7) and G. G. Reissaus  (25).  The ap-  paratus used was m o d i f i e d i n the f o l l o w i n g manner:-The s t a n d ard c e l l , composed of a p l a t i n u m e l e c t r o d e wire ,'• and a few  Reference I CiectJrode  1*0  .wipe.. 300  o  volume  & dded  Pl&binum too  Kqi  volume K^Ff'lCN) solubfon in c.c 6  _j.oitilL„ O- Hoc <J ;S  000  <XbM7J£  A.E1ZAC  "electrode:  volume* added -  .100.  12,  16  .  i<  volume K^feC?N) • soVljiorv m ccj 6  16 cc's .pf.K^e(GN) * s o l u t i o n (40cc's of' K Fe(CN)g s t a n d a r d and 4  2cc's o f c o n c e n t r a t e d HgSO^) i n a s m a l l g l a s s tube w i t h a p l a t i n u m s e a l at. the bottom, was i n s e r t e d i n t o a t e s t tube of s a t u r a t e d KG1  s o l u t i o n , to which had been j o i n e d two inches of  g l a s s t u b i n g w i t h a ground g l a s s j o i n t at i t s bottom.  During  the t i t r a t i o n of the z i n c w i t h the K^Fe(CN) ^ s o l u t i o n , t h i s ground g l a s s j o i n t was dipped i n t o the s o l u t i o n , and the r e s u l t i n g changes i n p o t e n t i a l measured by means of a Beckmann pH meter and a v o l t a g e extender.  I n t h i s way the s a l t b r i d g e s  and standard c e l l were combined i n t o a s i n g l e convenient unit.' Apart from t h i s , the procedure was the same as they d e s c r i b e d . Xanthate D e t e r m i n a t i o n Xanthates were determined'by  potentiometric t i t r a t i o n  w i t h i o d i n e , u s i n g a calomel and a p l a t i n u m e l e c t r o d e . The •• xanthate i o n was o x i d i z e d q u a n t i t a t i v e l y to dixanthogen  and  the presence of f r e e i o d i n e at the end-point d e t e c t e d by the p o t e n t i a l of the h a l f c e l l , P t { I , I ~ ) . g  T h i s was used i n p r e f -  erence- t o a .starch i n d i c a t o r , as some o f the m e t a l ions p r e vent an a c c u r a t e end-point.  A Beckmann pli meter, w i t h c a l -  omel and p l a t i n u m e l e c t r o d e s , was used i n t h i s d e t e r m i n a t i o n , and gave a sharp end-point w i t h a change i n r e a d i n g s o f about five units.  I t was o f t e n necessary t o wait almost f i v e  minutes  t o o b t a i n constant r e a d i n g s a f t e r each a d d i t i o n when c l o s e t o the end-point.  However,' d e s p i t e this-, the d e t e r m i n a t i o n s were  q u i c k l y and a c c u r a t e l y c a r r i e d o u t , and the- end-points found by p l o t t i n g A l / A G a g a i n s t c o n c e n t r a t i o n .  17 Copper and I r o n  Determinations  Copper was determined i n the c o n v e n t i o n a l manner w i t h K I and NagSgOg, w h i l e i r o n was found by t i t r a t i n g w i t h KMnO,.  18 FLOTATION TESTS Tests i n a s m a l l f l o t a t i o n c e l l , as d e s c r i b e d by R. 1. Bennett (1) were used t o measure the f l o a t a b i l i t i e s of the •minerals.  S i n c e f l o t a t i o n i s thought t o be due to the ore  p o s s e s s i n g a hydrophobic s u r f a c e , these t e s t s were, considered t o i n d i c a t e the c o n d i t i o n of the s u r f a c e , and to g i v e a measure of i t s degree of water r e p e l l e n c e , or f l o a t a b i l i t y .  Fur-  t h e r , i t was hoped to o b t a i n an i d e a of the behavior of the ore under c e r t a i n c o n d i t i o n s * which would, i n f u t u r e serve as a guide to the s t a t e of the orei-:."For i n s t a n c e , i t was necess a r y t o know whether'the ore c o u l d be c o n s i d e r e d to be I n an a c t i v a t e d or d e a c t i v a t e d s t a t e .  Since these terms had been  used t o d e s c r i b e ore used I n a l k a l i n e m i l l c i r c u i t s , u s u a l l y about a p'H of 9 or h i g h e r , a c t i v a t e d s p h a l e r i t e was c o n s i d e r ed t o be that which f l o a t e d at t h i s pH, w h i l e unactivated. or d e a c t i v a t e d s p h a l e r i t e was t h a t which d i d not f l o a t at t h i s pH. For t h i s work, s e v e r a l samples of s p h a l e r i t e were a v a i l able.  Two o f t h e s e , both copper f r e e , but c o n t a i n i n g c o n s i d -  e r a b l e i r o n were s e l e c t e d f o r the f o l l o w i n g work, most of which was done w i t h Sample #2, .as there was i n s u f f i c i e n t time In most cases t o d u p l i c a t e the work w i t h Sample #3. Sample #£—57.8% Zn and. 7.6% Fe. Sample #3—60.8% Zn and 5.5% Fe. I n both samples t h e r e were s m a l l q u a n t i t i e s of antimony and cadmium, w i t h a l s o a t r a c e of a r s e n i c .  Of Sample #2,  19 a p p r o x i m a t e l y 1$ was i n s o l u b l e i n d i l u t e HG1 s o l u t i o n . Samples f o r these t e s t s were prepared by g r i n d i n g f o r 1/2 t o 3/4 o f an hour i n a b a l l m i l l and then s i z i n g t h e ore by means o f an e l u t r i a t o r t u b e .  The e l u t r i a t o r tube c o n s i s t e d  o f a t a l l g l a s s c y l i n d e r , 7.3cm i n diameter, s t a n d i n g i n a large evaporating dish.  Water was passed i n t o t h i s a t the  bottom by means of a l o n g g l a s s t u b e , a t a constant r a t e .  The  o v e r f l o w was c a r r i e d down t o t h e l a r g e e v a p o r a t i n g d i s h by means o f a s i p h o n .  The ground mineral, was p l a c e d i n t h e c y l -  i n d e r , and t h a t which was c a r r i e d over when t h e r a t e of a d d i t i o n o f the water was 170cc's per minute, o r h a v i n g an upward v e l o c i t y of 4cm p e r minute i n the c y l i n d e r , was d i s c a r d e d . The r a t e o f f l o w was then i n c r e a s e d t o 500ec's per minute, or an upward v e l o c i t y o f 12cm per minute* and t h e ground m a t e r i a l which o v e r f l o w e d w i t h the water,-'and s e t t l e d out i n the evapo r a t i n g d i s h , was saved f o r the t e s t s .  Thus the ore sample®•-?j£.r;v  used were composed o f p a r t i c l e s h a v i n g a s e t t l i n g r a t e bf 4 t o 12cm per minute.  M i c r o s c o p i c examination showed these  p a r t i c l e s t o be i r r e g u l a r and f l a k y i n shape, r a n g i n g i n s i z e from 5 t o 30 microns a c r o s s . F l o t a t i o n t e s t s were conducted as f o l l o w s : The c e l l ¥/.as f i l l e d w i t h the s o l u t i o n t o be used, and a i r s u p p l i e d a t a p r e s s u r e o f 40cm of mercury as i n d i c a t e d by a manometer*  The ore sample was then put i n t o the c e l l , and  s o l u t i o n added u n t i l the f r o t h * which, was then, skimmed o f f with a spatula, just overflowed.  The t e s t l a s t e d f i v e m i n u t e s ,  u n l e s s a dark f r o t h i n d i c a t e d t h a t f l o t a t i o n was s t i l l  taking  30 p l a c e , t,hus r e q u i r i n g more time*  U s u a l l y f i v e minutes was s u f -  f i c i e n t , and at the end white f r o t h covered t h e c e l l .  Sol-  u t i o n was added v/hen necessary t o keep the f r o t h h i g h enough to j u s t o v e r f l o w .  The s o l u t i o n used contained 25cc's of t e r -  .pineol s o l u t i o n (250mg/l) as a f r o t h e r * and 25cc's KEtX s o l u t i o n (mg/ce) as a c o l l e c t o r per l i t r e .  T e s t s showed 25cc's  of KEtX s o l u t i o n t o be s u f f i c i e n t , as h i g h e r c o n c e n t r a t i o n s gave no a d d i t i o n a l r e c o v e r y * RESULTS OF FLOTATION TESTS Recovery  % 7.1  EEtX mg/l  pH  0  5.. 8  83  25  6  83  100  6  •. . Comments  10.4  25  9.5  68.6  25  8.6-  Ore prewashed w i t h CuSO^ s o l .  88  25.  6  23mg K C N / l i t r e added  77.4  25  6.4  ;115mg K C N / l i t r e added  9  25  9  23mg K C N / l i t r e added  71*5  25  5.2  Prewashed w i t h 0*003N KCN  7.2  25  8.8  Prewashed w i t h 0.003N KCN  72  25  5.8  Prewashed w i t h CuS0 s o l ' n and 2 3 m g / l i t r e KCN .added  12.6  35  8.6  Prewashed w i t h CuS0 s o l ' n and 2 3 m g / l i t r e KCN added  4  4  The above t e s t s were conducted f o r the most p a r t i n a pH range of from 5 t o 7 or from 8 t o 10, because i t was found t h a t the u n t r e a t e d s p h a l e r i t e f l o a t e d i n the former range, and  because the h i g h e r pH range could be used t o i n d i c a t e whether the ore was a c t i v a t e d or d e a c t i v a t e d . Good r e c o v e r y o f about 80% was obtained f o r a pH of 6, w h i l e a r e c o v e r y o f o n l y 10% was obtained at a pH o f 9.5, thus i n d i c a t i n g the ore t o be u n a c t i v a t e d *  The presence of  cyanide i n the s o l u t i o n , or prewashing the ore i n very d i l u t e cyanide s o l u t i o n d i d not a f f e c t the r e s u l t s f o r these pH's. Prewashing the ore w i t h CuSO^ s o l u t i o n gave a good r e c o v e r y f o r a pH o f '8.6, w h i l e the presence o f cyanide r e t u r n e d the f l o a t a b i l i t y of the ore t o t h a t o f the u n a c t i v a t e d m i n e r a l . I n t h e s e . t e s t s , the cyanide does not seem to a f f e c t the una c t i v a t e d ore but o n l y t o d e a c t i v a t e t h e CuSO^ t r e a t e d o r e s . I n order t o examine more f u l l y the p a r t p l a y e d by z i n c sulphate formed by the o x i d a t i o n o f s u l p h i d e a t the m i n e r a l s u r f a c e , samples were washed I n d i l u t e H^SO^, and then by means o f a Buchner f u n n e l f u r t h e r washed w i t h a  continuous  stream o f d i s t i l l e d water, u s i n g a t l e a s t two l i t r e s , p r i o r to t h e f l o t a t i o n t e s t .  I n a d d i t i o n , a few samples were t r e a t -  ed f o r f i v e minutes i n warm N/10 KGN s o l u t i o n * about 60°C, f  f i l t e r e d , and xrashed w i t h l e s s than 5 0 c c s of d i s t i l l e d water before the t e s t .  N i t r o g e n was used i n some o f the f l o t a t i o n  t e s t s to prevent r e d x i d a t i o n o f the m i n e r a l s u r f a c e *  22 R e s u l t s of; F l o t a t i o n Tests on A c i d Washed Ore...Samples Recovery  KEtX mg/1  o  1.  58  2.  36.4 •V  pH  . ,  Comments.  0  .6*5  0  5.4  Used a i r i n c e l l , added 2 3 m g / l i t r e of, KCN  •  Used a i r i n c e l l  3.  24.1  0  9.5  Used a i r i n c e l l , added 2 3 m g / l i t r e o f KCN  4.  50.1  0  7.1  Used Ng i n c e l l  5.  37.8  0  8  Used N i n c e l l , added 2 3 m g / l i t r e KCN  6.  34  .  0  ,  -6.5  g  . N  g  i n c e l l , added 23mg/l KCN  The f o l l o w i n g ore samples were washed i n warm KCN:,N/10 s o l , 7. -  36 -40.2  0  6,5.  Passed a i r through pulp i n c e l l f o r l/2hr p r i o r to test,  0  5.9  Added 2 5 m g / l i t r e KEtX and r a n t h i s t e s t on t a i l i n g s  8.  69.6  0-  7  Used Ng i n c e l l  9.  33.5  0  6.4  Used N  ?  i n c e l l , added 23mg/l  . ' 'ECET I n t e s t # 5 — O n l y 13$ a d d i t i o n a l r e c o v e r y hy adding 25mg/l KEtX and r u n n i n g an a d d i t i o n a l 5 minutes*  Addition of a c o l -  l e c t o r d i d not seem to i n c r e a s e r e c o v e r y as. t h e r e w a s ' ' s t i l l very s l i g h t f l o t a t i o n t a k i n g p l a c e , p r i o r to t h i s a d d i t i o n , and t h i s w i t h the m e c h a n i c a l l y  c a r r i e d over ore c o u l d e a s i l y  amount t o .13$ These t e s t s showed t h a t r e c o v e r i e s i n excess of 50$, using  a i r or n i t r o g e n i n the c e l l , c o u l d be obtained w i t h the  a c i d washed o r e , as compared t o r e c o v e r i e s of l e s s than 10$  23 u s i n g the, u n t r e a t e d m i n e r a l .  Thus the cleaned s u l p h i d e min-  e r a l possessed a n a t u r a l f l o a t a b i l i t y once t h e s o l u b l e s u r f a c e sulphate s a l t was removed.  Test #5 showed t h a t the c o l l e c t o r  had no a d d i t i o n a l e f f e c t upon the cleaned m i n e r a l s u r f a c e * and thus s u b s t a n t i a t e d the c l a i m t h a t a s o l u b l e zinc, s a l t , ' ZnSO^j was necessary f o r the f o r m a t i o n o f a hydrophobic xanthate s u r f a c e l a y e r .  Test #7 showed t h a t the m i n e r a l  would o x i d i z e i n c o n t a c t w i t h a i r , without a c o l l e c t o r .  metal  and decrease the r e c o v e r y  However, the a d d i t i o n of 2 5 m g / l i t r e KEtX  gave a f u r t h e r r e c o v e r y of 40%, thus I n d i c a t i n g approximately the extent o f the o x i d a t i o n d u r i n g the h a l f hour t h a t a i r was passed through the c e l l .  The t o t a l r e c o v e r y , w i t h and without  c o l l e c t o r , was a p p r o x i m a t e l y t h e same as t h a t i n Test #8, u s ing  n i t r o g e n i n the c e l l .  These t e s t s show t h e n a t u r a l s u l -  phide s u r f a c e t o be v e r y d i f f e r e n t from the oxidized, s u r f a c e which i s n e c e s s a r y f o r f l o t a t i o n as p r a c t i s e d * Perhaps more important however, i s the p a r t p l a y e d by cyanide i n these t e s t s .  Ore pre washed i n warro.H/10 KC3ST s o l -  u t i o n gave an e x c e l l e n t r e c o v e r y when nitrogen-was used i n the f l o t a t i o n c e l l , thus i n d i c a t i n g cyanide t o have a c l e a n s i n g a c t i o n on the s u r f a c e .  F u r t h e r , i t c o u l d not have formed'a  h y d r o p h i l i c l a y e r of Zn(GB")g, as p r e d i c t e d by many, or i f such a l a y e r was formed, i t should be hydrophobic, and thus beneficial to flotation.  Secondly the presence of cyanide i n  the c e l l d u r i n g f l o t a t i o n d e f i n i t e l y decreased t h e r e c o v e r y . T h i s would i n d i c a t e t h a t the cyanide had some a d d i t i o n a l e f f e c t on t h e s u l p h i d e s u r f a c e .  Perhaps t h e f o r m a t i o n of a com-  24 ple'x z i n c cyanide s a l t , o c c u r i n g s l i g h t l y when i n contact w i t h cyanide i o n , had much the same e f f e c t as a s o l u b l e s u r f a c e salt.  However these t e s t s do i n d i c a t e , that i f such a z i n c  cyanide s u r f a c e s a l t i s formed, i t would be v e r y e a s i l y r e moved, and ?/ould not prevent the c o l l e c t o r from a c t i n g on the mineral.  ACTIVATION-AND DEACTIVATION' ' Tests •• .. T r i a l a c t i v a t i o n and d e a c t i v a t i o n t e s t s . w e r e conducted t o see which i o n s , and i n ' what q u a n t i t i e s were removed from s o l ution.  The procedure  c o n s i s t e d o f t r e a t i n g the ore w i t h a  s o l u t i o n o f known volume and c o n c e n t r a t i o n , f i l t e r i n g on a G o o c h . c r u c i b l e * and d e t e r m i n i n g the c o n c e n t r a t i o n o f the v a r i o u s i o n s t o see which" had been removed o r r e t u r n e d t o the solution.  The ore was f i r s t t r e a t e d w i t h GuSO^. i n t h i s manner  and then w i t h KON  solution.  Results A c t i v a t i o n Tests Cu I.  and l e  q u a n t i t i e s are r e p r e s e n t e d as the' s u l p h a t e s .  Sample o f 7.687g removed 5.61 mg of CuSO^.  No z i n c was r e -  t u r n e d .to s o l u t i o n , but i r o n was found p r e s e n t i n the f e r r o u s , state*  The ore was an u n s i z e d coarse sample.  Time of con-  t a c t was 15 minutes. I I . — S a m p l e c o n s i s t e d o f 15.021g o f s i z e d ore*  Of the 16.3g  of CUSO4 p r e s e n t , o n l y a b a r e l y d e t e c t a b l e amount o f 1 t o 2mg  25 was  l e f t . -,. I n i t s p l a c e , 5mgs of FeSO^ and no z i n c were found. A f l o t a t i o n t e s t on t h i s sample a t a pH o f 8-9 showed  good  recovery.  D e a c t i v a t i o n Test Sample c o n s i s t e d of 8.801g o f a c t i v a t e d ore from #2 a c t i v a t i o n t e s t , and was t r e a t e d with a s o l u t i o n c o n t a i n i n g :  14.8mg o f KCN.  There was 5.Q8mg of KCN l e f t , thus approxim-  a t e l y 9i7mg had been removed from s o l u t i o n . there was found 5.97mg o f C u S 0  4  I n the s o l u t i o n  (the Cu found i s expressed  here as CuSQ , d e s p i t e the f a c t t h a t i t was present 4  p l e x i o n w i t h CN.  as a com-  T h i s was shown by the f a c t t h a t i t was  n e c e s s a r y to evaporate the s o l u t i o n t o d r y n e s s , before any t e s t f o r Cu c o u l d be o b t a i n e d ) . A f l o t a t i o n t e s t on t h i s sample gave no recovery* An examination o f these r e s u l t s show the amount o f GuS0 absorbed from s o l u t i o n was g r e a t e r for••"the f i n e sample * 4  a f a c t a l r e a d y r e p o r t e d i n the l i t e r a t u r e .  The amount o f  FeSO^ r e t u r n e d t o t h e s o l u t i o n i n the a c t i v a t i o n process was approximately  r  l/3' of t h a t r e q u i r e d t o be c h e m i c a l l y  a l e n t t o the CuS0 removed. 4  equiv-  No z i n c was r e t u r n e d t o the s o l -  u t i o n , a f a c t which might be p r e d i c t e d from the s o l u b i l i t y —23 p r o d u c t s o f the r e s p e c t i v e s u l f i d e s , namely 1.2 x 10 for -19 z i n c s u l p h i d e and 3.7 x 10  for ferrous sulphide. ,  I n t h e d e a c t i v a t i o n p r o c e s s , 5.97mg o f GuSO^ were r e turned t o s o l u t i o n , and 9.7mg o f KCN removed. KCN  The amount o f  r e q u i r e d t o remove the Cu as Cu(CN)5 was 7.3mg, about  26 2.3mg l e s s than t h a t a c t u a l l y used up.  F u r t h e r the amount  of GuSO^ r e t u r n e d t o s o l u t i o n was o n l y approximately 2/3 of t h a t adsorbed i n the a c t i v a t i o n process (note:-although cyani d e removed I s r e f e r r e d t o throughout as KCN  i t i s o n l y the  cyanide i o n which i s a b s t r a c t e d from the s o l u t i o n ) .  XANTHATE'ABSTRACTION TESTS  .•  By these t e s t s , i t had been hoped t o determine the  am-  ount o f xanthate removed from the s o l u t i o n by the ore under d i f f e r e n t c o n d i t i o n s , and p a r t i c u l a r l y t o see i f the presence of cyanide a f f e c t e d t h i s q u a n t i t y . The method f o l l o w e d was t o prepare a s o l u t i o n of 150cc's c o n t a i n i n g 25cc's of EEtX s o l u t i o n , a d j u s t the pH, and then s t i r lOOcc's of t h i s w i t h ,15g o f ore f o r 10 minutes.  The s o l u t i o n was then f i l t e r e d  on a Gooch c r u c i b l e , and the f i l t r a t e t i t r a t e d w i t h i o d i n e . X t was found t h a t i f the sample was l e f t in.the. s o l u t i o n , no end-point was o b t a i n e d .  I n a d d i t i o n t o t h i s , t h e r e was a l -  ways present some g r a y i s h white c o l l o i d a l s p h a l e r i t e which i n t e r f e r r e d w i t h the e n d - p o i n t , c a u s i n g i t t o be not so d i s t i n c t , and to be o b t a i n e d o n l y a f t e r an e x c e s s i v e q u a n t i t y o f Ig s o l u t i o n had been added.  A b i g i n i t i a l drop i n p o t e n t i a l  a f t e r ' l o p o f I g s o l u t i o n had been added, was noted when a s o l u t i o n o f the c o l l o i d a l m a t e r i a l was t i t r a t e d .  This indicated  t h a t the i o d i n e was. b e i n g used up s l o w l y , thus p r e v e n t i n g an a c c u r a t e d e t e r m i n a t i o n o f the xanthate p r e s e n t . T i t r a t i o n s of xanthate s o l u t i o n s c o n t a i n i n g s m a l l amounts o f z i n c , f e r r o u s ; and f e r r i c i o n t o see i f two end-points i n -  27 & i e a t i n g . K E t X .and metal xanthate would occur, gave o n l y one end-point corresponding t o the t o t a l xanthate. ' I n each case, t h e r e was a f a i n t ^ o p a l e s c e n c e i n d i c a t i n g the f o r m a t i o n of the i n s o l u b l e metal xanthates.  A l l o f these t h r e e xanthates  much more s o l u b l e than P b ( E t X )  g  with F e ( E t X )  3  are  being the most  s o l u b l e o f the t h r e e * Because of the c o l l o i d a l s p h a l e r i t e p r e s e n t , i t was  de-  c i d e d t o add the Ig s o l u t i o n at a constant r a t e , and take r e a d i n g s at p e r i o d i c i n t e r v a l s .  From the time v a l u e s , the  volume of Ig s o l u t i o n added, c o u l d be found. the c o l l o i d a l m a t e r i a l  In t h i s  way,  would not be able t o hide the  end-  p o i n t by the slow u s i n g up of i o d i n e .  T h i s method does not  a l l o w f o r e q u i l i b r i u m r e a d i n g s i n the r e g i o n of the  end-point,  or f o r s m a l l a d d i t i o n s t o enable a more a c c u r a t e d e t e r m i n a t i o n yet the r e s u l t s were i n d i c a t i v e of the r e l a t i v e amounts of xanthate removed from s o l u t i o n .  T i t r a t i o n s to determine  the  e r r o r from the f i r s t source showed i t t o amount, to l / 2 c e f o r a f a i r l y f a s t a d d i t i o n to l | c c f o r a slow a d d i t i o n *  !  R e s u l t s of Xanthate A b s t r a c t i o n T e s t s w i t h KEtX o n l y i n Solution (In a l l cases KEtX present was Ig  s o l u t i o n — a t a pH of 5-6,  e q u i v a l e n t to 9cc's of  which.should  give f l o t a t i o n - -  samples o f 14 t o 17g required' a p p r o x i m a t e l y 7. 5cc' s of I u t i o n - ( a f a i r l y sharp end-point was At a pH of 8-10, les  sol-  obtained).  which should not g i v e f l o t a t i o n — s a m p 1  o f 16g to 20g r e q u i r e d a p p r o x i m a t e l y 1 2 . 5 e c s of I  ution.  g  g  sol-  sbuipvajj  Jarful  w  28 F o r c o n d i t i o n s under which f l o t a t i o n should take p l a c e , approximately 5cc's o f I  g  s o l u t i o n * or 4.6mgs o f KEtX, r e p r e -  sented the a d d i t i o n a l xanthate removed from s o l u t i o n . With KCN i n S o l u t i o n No s a t i s f a c t o r y end-points were obtained w i t h cyanide i n s o l u t i o n , due t o the a c t i o n o f i o d i n e on cyanide.  Solutions  o f K l t X and KCN f a i l e d to g i v e s a t i s f a c t o r y end-points when t i t r a t e d with Ig s o l u t i o n s .  However, end-points  obtained  were a p p r o x i m a t e l y , S l c c ' s f o r a pH o f 5-6 and 22-24cc*s'for a .  pH o f 8-9. Values obtained w i t h o n l y KEtX present T/ere l a t e r cheeked by t e s t s i n which "the c o l l o i d a l s p h a l e r i t e was removed w i t h a Zeiss f i l t e r ,  -These values w i t h two obtained w i t h KCN p r e -  sent are shown i n F i g . IV. I n a d d i t i o n , an attempt was made t o remove the xanthate l a y e r by means of an o r g a n i c s o l v e n t , and then determine t i t r a t i o n - a s above.  i t by  These attempts proved u n s u c c e s s f u l , a l -  though by u s i n g acetone, and e v a p o r a t i n g almost t o dryness by means of a water pump, the amount removed was e q u i v a l e n t t o l i c e ' s of I g s o l u t i o n , or 1.47mg of KStX.  There were a l s o  i n d i c a t i o n s t h a t some of the xanthate removed had been decomposed d u r i n g the e v a p o r a t i o n . Cyanide A b s t r a c t i o n T e s t s Ore samples were s t i r r e d m e c h a n i c a l l y f o r 15 minutes w i t h lOQcc's o f s o l u t i o n c o n t a i n i n g a known amount, o f KCN at a g i v e n pH.  These s o l u t i o n s were then f i l t e r e d i n t o a Gooch ,  29 c r u c i b l e , and the f i l t r a t e analyzed f o r cyanide s t i l l remaining.  From these t e s t s i t was hoped t o determine i f the am-  ount removed depended upon weight o f sample and pH, or i f cyanide was removed u n t i l a c e r t a i n c o n c e n t r a t i o n of cyanide ion  remained i n e q u i l i b r i u m w i t h the sample at the d i f f e r e n t  pE's.  C o l l o i d a l ore i n the f i l t r a t e  could not be avoided.  At the s t a r t t h i s e f f e c t was c o n s i d e r e d n e g l i g i b l e , and the values were not c o r r e c t e d i n any way.  L a t e r t e s t s were c o r -  r e c t e d f o r t h i s i n e i t h e r one of two ways, f i r s t by running a blank on the c o l l o i d a l m a t e r i a l , and secondly by a l l o w i n g the f i l t r a t e to stand at l e a s t 48hrs to a l l o w the c o l l o i d a l m a t e r i a l t o s e t t l e , and a l s o a l l o w i n g the coloured sample t o stand i n ' o r d e r t h a t the s t i l l remaining c o l l o i d might coagulate and s e t t l e . R e s u l t s o f Tests In a l l t e s t s lOOcc's of s o l u t i o n c o n t a i n i n g .0986mg/cc KCN was used. pH  Wt. of Sample g  Final conc'n rng/cc  Orig'l conc'n Big/ c c  mg/g Ore removed mg/g •  1. 9.3  6.1394  .0710  .0986 .  .450  4.5  6.7696  .0786  .0986  .296  3. 10.3  14.1190  .0775  .0986  .149  !•  4.1  8.2.707  .0490  .0986  .599  5."  8.5  8.823  .0495  .0986  .556  4.1  9.2630  .0565  .0986  .455  Comments  Shaken i n enclosed Erlenmeyer »»  KEtX p r e s ent i n s o l .  30 A l l the above s o l u t i o n s c o n t a i n an e r r o r due t o the p r e sence of c o l l o i d a l s p h a l e r i t e , which blank d e t e r m i n a t i o n s showed t o be equal t o .01 t o ,02mg/cc of KCN, and w i t h a v a r i a t i o n i n each e r r o r of not g r e a t e r than .Olrng/cc KCN.  Thus  a l l f i n a l c o n c e n t r a t i o n s o f KCN are e x c e s s i v e by t h i s amount. The f o l l o w i n g values were c o r r e c t e d f o r c o l l o i d a l m a t e r i a l . Wt-, Sample S  Final cone. mg/ cc  Orig. Cone. mg/cc  6  11.1945  .0318  .0986  .521  9.5  10.834  ,0648  .0986  «312  10.2  15.914  .066  ,0986  .205  .0704  .652  .0704  .072  PH.  1>  10.  9.4  5.3065  11.  9.55  15.351 *  .0638 .059  mg/g Ore Removed mg/g #7 & #8 and-:;#9 c o r r e c t e d by standing.  #10 & #11 corrected with blanks.  A glance at the above f i g u r e s w i l l show t h a t the amount of cyanide removed to be dependant upon the f i n a l c o n c e n t r a t i o n r a t h e r than upon the weight  o f sample p r e s e n t .  They a l s o i n -  d i c a t e c o n s i d e r a b l e l o s s of cyanide i n t o the a i r at the lower pH's.  Comparison of t e s t #2, conducted  i n an enclosed e r l e n -  meyer, w i t h o t h e r s , i n d i c a t e d the lower values f o r a c i d pH's to be almost e n t i r e l y due t o t h i s  source.  A d d i t i o n a l t e s t s were conducted, t o determine  the concen-  t r a t i o n of z i n c and i r o n present i n s o l u t i o n s of d i s t i l l e d water, KEtX s o l u t i o n s , and s o l u t i o n s o f KEtX and KCN, which had been s t i r r e d f o r 2hrs i n c o n t a c t w i t h the o r e .  31 Results Solution  Conc'n of Fe  Conc'n of Zn  D i s t i l l e d Water  l - 2 m g / l i t r e Zn  37.2mg/litre  Fe  25mg/l KEtX S o l ' n  l - 2 m g / l i t r e Zn  15.9mg/litre  Fe  Sol'n containing 25mg/l KEtX and 23mg/l KCN  9.8mg/litre  Zn  l . S m g / L i t r e Fe  These r e s u l t s would i n d i c a t e t h a t the cyanide removed from s o l u t i o n , formed a s o l u b l e z i n c cyanide t h a n a s u r f a c e s a l t on the m i n e r a l .  complex, r a t h e r  Thus any i n f l u e n c e cyan-  i d e would have on the u n a c t i v a t e d s p h a l e r i t e should be due t o t h i s c l e a n s i n g a c t i o n , r a t h e r than -due t o p r e v e n t i n g the f o r mation o f a s u r f a c e xanthate s a l t on the m i n e r a l  surface.  l a y e r by a z i n c cyanide  complex  32  SUMMARY OF RESULTS The  r e s u l t s presented  were obtained from f l o t a t i o n t e s t s  a c t i v a t i o n and d e a c t i v a t i o n t e s t s , xanthate and cyanide a b s t r a c t i o n t e s t s .  abstraction tests,  B r i e f l y they i n d i c a t e the  fol-  lowing:I.  That cyanide does not a f f e c t the r e c o v e r y of unact-  i v a t e d s p h a l e r i t e . I t depresses the r e c o v e r y of a c t i v a t e d s p h a l e r i t e t o t h a t of the u n a c t i v a t e d m i n e r a l by the removal of the a c t i v a t i n g c u p r i c s u l p h i d e l a y e r .  The  copper thus r e -  moved I s i n the form of a complex copper cyanide s a l t .  (G-au-  d i n has s t a t e d t h i s to be GuCCN)^) II. or KCN  The  s u l p h i d e m i n e r a l s u r f a c e , cleaned by an a c i d  wash, i s f l o a t a b l e .  O x i d a t i o n by a i r w i l l s l o w l y r e n -  der t h i s s u r f a c e u n f l o a t a b l e .  The  presence of cyanide  u t i o n decreases the f l o a t a b i l i t y of t h i s s u r f a c e .  in sol-  The  oxid-  i z e d s u r f a c e , presumably because of the presence of s o l u b l e ZnSO^ i s necessary  f o r a c t i o n with the c o l l e c t o r , l e a d i n g to  f o r m a t i o n of an i n s o l u b l e m e t a l xanthate III.  surface l a y e r .  Xanthate was a b s t r a c t e d from s o l u t i o n s i n g r e a t e r  q u a n t i t y under c o n d i t i o n s f o r which f l o t a t i o n of s p h a l e r i t e would take p l a c e *  The presence of cyanide prevented  d e t e r m i n a t i o n of xanthate t h a t e was 17.  abstracted.  The  accurate  s u r f a c e metal xan-  a b s t r a c t e d w i t h acetone, although not q u a n t i t a t i v e l y . A b s t r a c t i o n t e s t s showed cyanide t o be removed  from s o l u t i o n , depending upon the pH of the s o l u t i o n and  final  c o n c e n t r a t i o n of cyanide r a t h e r than upon the weight of ore,  53 or area of m i n e r a l s u r f a c e .  The  cyanide removed appeared t o  be present i n the s o l u t i o n i n the form of a s o l u b l e z i n c anide complex. m a i n l y due The  Cyanide removal i n s o l u t i o n s of a c i d pH  cywas  t o l o s s i n t o the a i r . a c t i o n of cyanide i s m a i n l y a c l e a n s i n g a c t i o n , r e -  moving the c u p r i c s u l f i d e l a y e r i n the case of a c t i v a t e d s p h a l e r i t e and removing some of the s o l u b l e z i n c s u l f a t e from the s u r f a c e  i n the case of the u n a c t i v a t e d  mineral.  'ter e f f e c t i s not pronounced enough at the d i l u t e  This l a t concentrati-  ons e x p e r i e n c e d i n f l o t a t i o n , t o i n f l u e n c e the r e c o v e r y . d e f i n i t e l y does not prevent f l o t a t i o n , as has  It  o f t e n been sug-  g e s t e d , by the f o r m a t i o n of a h y d r o p h i l i c l a y e r of z i n c cyani d e i n p l a c e of a water r e p e l l e n t l a y e r of z i n c e t h y l xanthate.  34  REFERENCES 1,. "The Surface Chemistry of F l o t a t i o n — R . L. Bennett. T h e s i s submitted f o r M. A. So, U n i v e r s i t y  of B r i t i s h  Columbia', 1938. 2.  " F l o t a t i o n " — I . W. Wark.  3.  American I n s t i t u t e of M i n i n g and M e t a l l u r g i c a l Engineers (Trans), (a)  V o l . 112.  P r i n c i p l e s o f F l o t a t i o n I--An Experimental! Study o f . t h e E f f e c t of Xanthates on Contact Angles at M i n e r a l S u r f a c e s - - ! . W. Wark & A. B. Cox*  (b)  pl89,  P r i n c i p l e s o f F l o t a t i o n I I — A n E x p e r i m e n t a l Study, of the I n f l u e n c e of Cyanide, A l k a l i s , and Copper Sulphate on the E f f e c t o f Potassium E t h y l Xanthate :  at M i n e r a l Surfaces''— -I. W. Wark & A. B. Cox, p245. (c)  P r i n c i p l e s o f F l o t a t i o n I I I — A n E x p e r i m e n t a l Study on the I n f l u e n c e of Cyanide, A l k a l i s , and Copper  - S u l p h a t e  on the E f f e c t o f Sulphur b e a r i n g C o l l e c t o r s  at M i n e r a l S u r f a c e s — I . W. Wark & A. B. Cox, (d)  R e a c t i o n s of Xanthates w i t h S u l p h i d e M i n e r a l s - - — A . M. Gaudin* F, Dewey,  W. E. Duncan* R. A.  Johnson, & 0* F. T a n g e l , J r . (f)  p319.  A c t i o n o f A l k a l i Xanthates on G a l e n a — T . G. T a y l o r , F  & A. . K n o l l . 4.  p267.  p382.  9  G. A. — 3 0 > 6 6 7 9 — T h e E f f e c t o f Hydrogen I o n Concentrati o n on F l o t a t i o n of S p h a l e r i t e (Unavailable reference)  Yamada and Vaganuma.  References  cont'd.  5.  " F l o t a t i o n " — A. M. Gaudin > 1932.  6.  American I n s t i t u t e of M i n i n g & M e t a l l u r g i c a l  Engineers.  V o l . 87. (a) . Chemical R e a c t i o n s i n F l o t a t i o n T, G. Tayor & A. F. K n o l l , (b)  A. F. Taggart,  p217.  A Study of. D e f f e r e n t i a l F l o t a t i o n - - G. R. Ince. ' - p261.  .(c)  Experiments w i t h F l o t a t i o n R e a g e n t s — A. F. Taggart, T. 0. T a y l o r , & G.R. I n c e ,  (d)  Activation  of S p h a l e r i t e f o r F l o t a t i o n — — G. C.  Ralston & G , 7.  J o u r . Phys. Ghem. Sulphur-bearing  p285.  Hunter j  p401.  37, 833, 45, "Surface A c t i o n s of Some  Organic Compounds on Some F i n e l y Ground  S u l p h i d e M i n e r a l s " - - - A. M. Gaudin &•¥*'£>. W i l d i n s o n . 8.  J o u r . Phys. Chem.  v o l . 36, 1.30, 1932. " M i n e r a l F l o t -  a t i o n " — - A . F. Taggart. 9.  Eng. & Min. J o u r . o f Depressors  v o l . 135, p350, 1934. "The F u n c t i o n  and P r o t e c t i v e Agents i n C o n d i t i o n i n g f o r  F l o t a t i o n - - - - - - G. R. M. D e l G u l d i c e . 10*  J o u r . Phys. Ghem.  40, p799,  1936. "The P h y s i c a l Chem-  i s t r y o f F l o t a t i o n V I I I — - E. E. Wark and I . W. Wark. 11.  Eng. & Mini- J o u r .  v o l . 133, p276,  1932.  "Depression  by Cyanide i n F l o t a t i o n C i r c u i t s " - — T. B. B r i g h t o n , G. Burgener, & J . Gross. 12.  J o u r . Phys. Chem.  v o l . 38, 15-18*  1934. " A d s o r p t i o n of  Copper Sulphate-by  S p h a l e r i t e and i t s R e l a t i o n t o F l o t a t i o n "  References cont'd 15.  T r a n s a c t i o n s o f the Canadian I n s t i t u t i o n of M i n i n g and Metallurgy,  v o l . 29,  p251, 1926.  f o r F l o t a t i o n " - — G. G. 14.  McLachlan.  Chem. & F l o t . P r o c e s s — American Cyanide Co. Tech. Paper No. 17, 1 9 3 0 —  15.  C. A. 33,  9221  Christmann. .  " P h y s i c o c h e m i c a l Role of A i r i n the  F l o t a t i o n of Non-ferrous Ores, 16.  "Synthetic Testing  Pt I I  A. M a l i n o v s k i .  American I n s t i t u t e of M i n i n g & M e t a l l u r g i c a l E n g i n e e r s V o l . 73.  " E f f e c t o f Cyanogen Compounds on F l o a t a b i l i t y of  Pure S u l f i d e M i n e r a l s " — - E . L. Tucker & R. E, Head. 17.  Trans, of E l e c t r o c h e m i c a l S o c i e t y ,  No 61,  p426,  1932.  "The P h y s i c a l Chemistry of F l o t a t i o n " — - I , W. Wark, 18.  A u s t r a l i a n I n s t i t u t e of M i n i n g and M e t a l l u r g y (Trans) No. 102,  pl02.  Flotation" 19.  M i n i n g Mag.  "On F u n c t i o n s of Chemical Reagents i n  by R. N e v e t t . v o l . 49, 1933  p317  "Sphalerite Flotation"  R. L. K i d d & W. A. W a l l . 20.  Z e i t s c h i f t f u r Anorganische Chemie, 1922.  v o l . 121,  p!78  "Die Electrometusche Bestimmung des Cyans neben  den Halogenen"-  E. M u l l e r & H, Lauterback.  U. S. Bureau of Standards-- J o u r n a l of Research No 7 913,  33,  1931.  " A n a l y s i s of Cyanide  Silver-plating  S o l u t i o n s " — R . M, Wick. 21.  Engineering & Mining Journal,  v o l 136,  p280, 1935,  "Determining Cyanide and Sulphocyanate i n S m a l l Amounts" by E. C. Boyman.  Reference 22.  cont'd  B u l l e t i n de La S o c i e t e Chimique (5) 2,  p845,  1935.  "Recherche du Eerrocyanure et des Products cyanes de l e Y i n Technique et L i m i t e d 23.  J o u r n a l of the American Chemical S o c i e t y , 1929.  v o l 51, p l l 7 1 ,  "A Method f o r the Q u a n t i t a t i v e Determination  Cyanide i n Small Amounts" 24.  Sinsibilite"  R. G Smith.  Z e i t s c h r i f t f u r A n a l y t i s c h e Chemie,  v o l 69,  "Bestimmung des Zink durch E l e c t r o m e t r i s c h e by G. G.  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