A simple kinetic model for sulfuric acid leaching of copper from chrysocolla
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ing the v o l u m e change d u r i n g the r e a c t i o n to be s m a l l o r n e g l i g i b l e . More r e d e n t l y , a model s i m i l a r to that p r o p o s e d by V a l e n s i s and Strangway, e t a l B i n v o l v i n g s t e a d y - s t a t e diffusion of the r e a c t a n t through the p r e v i o u s l y - r e a c t e d p o r t i o n of the o r e f r a g m e n t , followed by c h e m i c a l r e a c t i o n within a r e a c t i o n zone has b e e n f o r m u l a t e d by Wadsworth 9 and c o - w o r k e r s m which has b e e n shown to c o r r e l a t e well with e x p e r i m e n t a l data "~ ~ and l e n d s i t s e l f to b r o a d v a r i a t i o n s in g e o m e t r y . In its b r o a d e s t s e n s e , this m o d e l a s s u m e s r e a c t a n t s and p r o d u c t s of the l e a c h i n g p r o c e s s a r e t r a n s p o r t e d in s o l u t i o n - f i l l e d c h a n n e l s within the o r e f r a g m e n t . The model f u r t h e r a s s u m e s that c i r c u l a t i o n of leach s o l u tion around the p a r t i c l e is s u f f i c i e n t to m a i n t a i n r e q u i s i t e ion c o n c e n t r a t i o n so that bulk s o l u t i o n t r a n s p o r t is not r a t e c o n t r o l l i n g , and the k i n e t i c s a r e t h e r e f o r e l i m i t e d only by p r o c e s s e s o c c u r r i n g within the o r e particles. In the p r e s e n t i n v e s t i g a t i o n , the s h r i n k i n g - c o r e model ~'~~has been s i m p l i f i e d s o m e w h a t on c o n s i d e r ing the r e a c t i o n k i n e t i c s of l o w - g r a d e c h r y s o c o l l a . E x p e r i m e n t a l r e s u l t s of l o w - g r a d e c h r y s o c o l l a l e a c h ing a r e shown to c o r r e l a t e well with the p r o p o s e d s i m p l i f i e d model o v e r a wide r a n g e of p a r t i c l e s i z e s . The p r e v i o u s r e s u l t s of P o h l m a n and Olson ~ a r e also o b s e r v e d to be d e s c r i b e d by the p r e s e n t model, and to o v e r l a p with the p r e s e n t e x p e r i m e n t a l l e a c h i n g data. In this r e g a r d , the p r e s e n t study r e p r e s e n t s a s i g n i f i cant extension of the p r e v i o u s e x p e r i m e n t a l study of P o h l m a n and Olson. 1~ 1) D E V E L O P M E N T OF A SIMPLIFIED SHRINKING-CORE MODEL The s i g n i f i c a n t s t r u c t u r a l f e a t u r e s of the s h r i n k i n g c o r e kinetic model of o r e - p a r t i c l e l e a c h i n g proposed by Wadsworth, e t a l 9'1~ a r e that specific included m i n e r a l p h a s e s a r e p r e s e n t within the o r e p a r t i c l e as d i s c r e t e d i s s e m i n a t e d s u b p a r t i c l e s d i s t r i b u t e d throughout the p a r t i c l e or in v e i n l e t s which can be contacted by r e a c t a n t s t r a n s p o r t e d in s o l u t i o n - f i l l e d c h a n n e l s which s u r r o u n d the s u b p a r t i c l e s . The l e a c h i n g r e a c t i o n is e n v i s i o n e d to o c c u r within a r e a c t i o n zone which s e p a VOLUME 6B, SEPTEMBER
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