Aqueous oxidation of chalcopyrite in hydrochloric acid
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b e a c h i e v e d , f o r e x a m p l e , b y c e m e n t a t i o n with s c r a p i r on:
T H E R E have b e e n e x t e n s i v e s t u d i e s conducted r e cently on the l e a c h i n g of c h a l c o p y r i t e with the a i m of finding an e c o n o m i c a l h y d r o m e t a l l u r g i c a l r o u t e f o r c o p p e r that would not pollute the e n v i r o n m e n t . ~ Some of t h e s e p r o c e s s e s a r e e i t h e r in the p i l o t s t a g e o r a l r e a d y in c o m m e r c i a l p r o d u c t i o n . The following t h r e e p r o c e s s e s a r e t y p i c a l e x a m p l e s of the d i r e c t l e a c h ing of c h a l c o p y r i t e c o n c e n t r a t e s : 1) The S h e r r i t t - G o r d o n a m m o n i a p r o c e s s which is now d e v e l o p e d a s the A n a c o n d a - A r b i t e r p r o c e s s . 2) The f e r r i c c h l o r i d e p r o c e s s which i s now known a s the D u v a l p r o c e s s . 3) The S h e r r i t t - G o r d o n a c i d p r o c e s s which is now d e v e l o p e d a s the L u r g i - M i t t e r b e r g p r o c e s s . The f i r s t p r o c e s s 2'~ i n v o l v e s l e a c h i n g b y NH4OH in p r e s e n c e of 02 at 85~ and 710 k P a :
2 CuCI + F e --" 2 Cu + FeCI2. A f t e r f i l t r a t i o n , FeC12 can be o x i d i z e d to F e C I s by C12. The third process 6 involves leaching by dilute HsSO4 in an a u t o c l a v e at 115~ and u n d e r O2 p r e s s u r e of 3350 k P a : CuFeS2 + H2SO4 + 5/4 O2 ~ CuSO4 + FeOOH + 2 S + @HsO.
2 CuFeS2 + 12 NH3 + ~O2 + 2 H20 ---~ 2 Cu(NH3)4SO4 + 2 (NH4)2SO4 + FesOs.
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It has the a d v a n t a g e of o p e r a t i n g u n d e r n o n c o r r o d i n g conditions, and of k e e p i n g i r o n out of solution, but it has the d i s a d v a n t a g e of f o r m i n g (NH4)2804 which h a s to be e i t h e r m a r k e t e d a s f e r t i l i z e r o r d e c o m p o s e d by CaO to f o r m CaSO4 and r e g e n e r a t e NHa f o r r e c y c l e . The s e c o n d p r o c e s s 4'5 i n v o l v e s l e a c h i n g b y FeC13 s o l u t i o n at the b o i l i n g point and u n d e r a t m o s p h e r i c pressure: CuFeS2 + 4 F e C l a ~ CuCI2 + 5 FeC12 + 2 S.
[2]
It has the a d v a n t a g e of f o r m i n g e l e m e n t a l s u l f u r thus l i b e r a t i n g c o p p e r p r o d u c t i o n f r o m H2SO4 o r f e r t i l i z e r m a n u f a c t u r e , but has the d i s a d v a n t a g e that i r o n is d i s s o l v e d and has to be s e p a r a t e d , and f u r t h e r , the o x i d i z i n g a g e n t FeC13 has to be r e g e n e r a t e d , n a m e l y , by the o x i d a t i o n of FeC12. The s e p a r a t i o n of i r o n can FATHI HABASHI is Professor, Department of Mining and Metallurgy, Laval University, Quebec City G1 K7P4, Canada, and TEJ TOOR is Master, Haileybury School of Mines, Haileybury, Ontario P0J 1K0, Canada. Manuscript submitted April 4, 1978. METALLURGICAL TRANSACTIONS B
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It h a s the a d v a n t a g e that e l e m e n t a l s u l f u r i s f o r m e d , i r o n is kept out of s o l u t i
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