The recovery of osmium from nickel refinery anode slimes
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INVESTIGATIONS INTO THE RECOVERY O F OSMIUM The r e l a t i o n s h i p of o s m i u m to the other p r e c i o u s m e t a l s and b a s e m e t a l s which a r e r e c o v e r e d from Sudbury d i s t r i c t o r e s is i l l u s t r a t e d below: Periodic Groups VIII Fe Ru Os
Co Rh lr
Ni Pd Pt
IB
VIA
Cu Ag Au
S Se Te
O s m i u m was f i r s t i s o l a t e d and n a m e d in 1804 by T e n n a n t . 4 Its name is of G r e e k o r i g i n and m e a n s s m e l l or odor which the d i s c o v e r e r p r o b a b l y a s s o c i a t e d with the c h l o r i n e - l i k e odor of o s m i u m tetroxide. The most outstanding c h e m i c a l p r o p e r t y of o s m i u m is its r e action with oxygen to form the tetroxide which m e l t s at 105~F and b o i l s at 268~ It is thus not s u r p r i s i n g that this m e m b e r of the group did not s u r v i v e the s e v e r e p y r o m e t a l l u r g i c a l o p e r a t i o n s long employed in the winning of nickel. In spite of the fact that o s m i u m was not r e p o r t i n g with the other p l a t i n u m group m e t a l s in the final r e fining o p e r a t i o n s and that some opinions were exp r e s s e d doubting its p r e s e n c e in the Sudbury o r e s , t h e r e was s t r o n g conviction by INCo R e s e a r c h p e r s o n nel that o s m i u m m u s t be p r e s e n t . In 1952 a n a l y t i c a l work u t i l i z i n g n e u t r o n a c t i v a t i o n c o n f i r m e d its p r e s e n c e , in minute c o n c e n t r a t i o n s , in the o r e s of the Sudb u r y d i s t r i c t . ~ In 1957, an a n a l y t i c a l s u r v e y u s i n g a s e n s i t i v e c o l o r i m e t r i c method 6 was made on s e l e c t e d s a m p l e s from v a r i o u s l o c a t i o n s in the m e t a l l u r g i c a l flowsheet. This s u r v e y showed the p r e s e n c e of osm i u m in s m e l t e r feed, t r a c e d its path through the v a r i ous p r o c e s s i n g s t e p s , and indicated the a r e a s where o s m i u m r e c o v e r y might be favorable. It was e s t a b l i s h e d that the m e t a l l i c f r a c t i o n from the matte s e p a r a t i o n p r o c e s s c a r r i e d not only the five f a m i l i a r p l a t i n u m - g r o u p m e t a l s , but also a significant amount of o s m i u m and that e l e c t r o l y s i s of the m e t a l l i c s c o n c e n t r a t e d all of the p l a t i n u m - g r o u p m e t a l s in the anode s l i m e s . However, m o s t of the o s m i u m app a r e n t l y was v o l a t i l i z e d d u r i n g the p r o c e s s e s then e m p l o y e d for the production of a h i g h - g r a d e p r e c i o u s metals concentrate. In the c o n v e n t i o n a l t r e a t m e n t for base m e t a l s r e VOLUME I,FEBRUARY 1970-431
m o v a l , the s l i m e s , a n a l y z i n g about 50 pet Cu and 10 pct Ni, w e r e d i g e s t e d with c o n c e n t r a t e d s u l f u r i c a c i d to s o l u b i l i z e the base m e t a l s . D u r i n g this sulfating o p e r ation the t e m p e r a t u r e often r e a c h e d 6
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