Measurement and correlation of solvent extraction equilibria. The extraction of copper by kelex 100
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GERALD L. BAUER is Group Leader, Process Development, Zimpro, Inc., Rothschild, WI 54474. THOMASW. CHAPMANis Professor, Department of Chemical Engineering, University of Wisconsin,Madison, WI 53706, where Gerold L. Bauer was formerly a Graduate Student. Manuscript submitted August 18, 1975. METALLURGICALTRANSACTIONSB
K e l e x 100 is a p a t e n t e d r e a g e n t p r o d u c e d by A s h land C h e m i c a l Company for e x t r a c t i o n of copper. ~~ It is a highly b r a n c h e d b e t a a l k e n y l 8 - h y d r o x y q u i n o l i n e with m o l e c u l a r weight of 311. T h i s s y s t e m is of p r a c t i c a l i n t e r e s t for copper l e a c h l i q u o r p r o c e s s ing, yet it is r e l a t i v e l y s i m p l e c h e m i c a l l y in that K e l e x 100 i s a s i n g l e c o m p o n e n t . Most o t h e r c o m m e r c i a l p r e p a r a t i o n s for copper e x t r a c t i o n , K e l e x 120 and m o s t of G e n e r a l M i l l s ' LIX r e a g e n t s , 4 a r e m i x t u r e s of r e a g e n t s and m o d i f i e r s . X y l e n e was c h o s e n as the o r g a n i c s o l v e n t f o r t h i s c a s e study b e c a u s e of its low t o x i c i t y and v o l a t i l i t y as w e l l as its c h e m i c a l s i m p l i c i t y r e l a t i v e to k e r o s e n e . Also, the a r o m a t i c n a t u r e of xylene should m i n i m i z e the addit i o n a l c o m p l i c a t i o n of s u l f u r i c acid e x t r a c t i o n u n d e r s t r i p p i n g c o n d i t i o n s .31 THERMODYNAMIC ANALYSIS OF M E T A L EXTRACTION T h e e x t r a c t i o n of copper by K e l e x 100 i n v o l v e s a c h e l a t i o n r e a c t i o n which may be w r i t t e n as Cu +2 + 2HR ~-~ CuR2 + 2H +
[1]
w h e r e the ionic s p e c i e s a r e i n the a q u e o u s p h a s e , HR is the a c i d i c f o r m of the K e l e x 100 i n x y l e n e , and CuR2 is the copper chelate i n the o r g a n i c p h a s e . M a r c u s and K e r t e s 13 have p r e s e n t e d a t h e r m o d y n a m i c f r a m e w o r k for d e s c r i b i n g such r e a c t i o n s , but it has s e l d o m b e e n u s e d for t r e a t i n g e x p e r i m e n t a l data in d e t a i l . T h e a n a l y s i s u s e d h e r e follows the a p p r o a c h of Gugg e n h e i m 14'~S to the t h e r m o d y n a m i c s of s o l u t i o n s . T h e e q u i l i b r i u m condition for R e a c t i o n [1] is PCuR2 + 2/~H~ -- pCu§
-- 2/~HR = 0
[2]
w h e r e ~ti i s the c h e m i c a l o r e l e c t r o c h e m i c a l p o t e n t i a l of s p e c i e s i. T h e s e a r e r e l a t e d to c o m p o s i t i o n by the form tz i = R T
ln(~xi~i)
[3]
w h e r e X~ is the s t a n d a r d - s t a t e a c t i v i t y of s p e c i e s i and is a f u n c t i o n only of t e m p e r a t u r e and the n a t u r e of the s o l v e n t . T h e c o m p o s i t i o n is e x p r e s s e d h e r e as mole f r a c t i o n xi, and Yi is the a c t i v i t y c o e f f i c i e n t . S u b s t i t u t i o n of [3] into [2] y i e l d s
VOLUME 7B, DECEMBER 1976-519
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