Electrolytic recovery of molybdenum from molybdic oxide and molybenum sesquisulfide
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An e l e c t r o l y t i c p r o c e s s for molybdenum e x t r a c t i o n in a KC1-KsMoC16 e l e c t r o l y t e (containing a p p r o x i m a t e l y 7.5 wt pct molybdenum) was i n v e s t i g a t e d u s i n g t h r e e types of anode feed - - n a m e l y , molybdic o x i d e - g r a p h i t e , molybdenum s e s q u i s u l f i d e - g r a p h i t e , and m o l y b d e n u m s e s q u i s u l f i d e without graphite. In the case of molybdic o x i d e - g r a p h i t e anode, a m a x i m u m c u r r e n t e f f i c i e n c y o f 9 9 p c t w a s achieved at an o p e r a t i n g voltage of 0.35V, a cathode c u r r e n t d e n s i t y of 5000 A / m ~ (450 A/f z) and a bath t e m p e r a t u r e of 1223 K. E l e c t r o l y s i s with m o l y b d e n u m s e s q u i s u l f i d e - g r a p h i t e , at an o p e r a t i n g voltage of 1.2 V, a cathode c u r r e n t d e n sity of 13,900 A / m z (1250 A/f 2) and a bath t e m p e r a t u r e of 1173 K, yielded a m a x i m u m c u r r e n t efficiency of 84 pet. E l e c t r o l y s i s of m o l y b d e n u m s e s q u i s u l f i d e without g r a p h i t e i n c o r poration, yielded u n d e r a l m o s t s i m i l a r conditions, a m a x i m u m c u r r e n t e f f i c i e n c y of 87 pet. Extended e l e c t r o l y s i s was c a r r i e d out using molybdic o x i d e - g r a p h i t e and m o l y b d e n u m s e s quisulfide cell c h a r g e s and yielded m e t a l with p u r i t y over 99.9 pct.
PROCESSES
for e x t r a c t i o n of molybdenum m e t a l by molten s a l t e I e c t r o l y s i s have d r a w n c o n s i d e r a b l e i n t e r e s t . Different t e c h n i q u e s s t a r t i n g with m o l y b d e n u m oxides and m o l y s u l f i d e have been r e p o r t e d in the l i t e r a t u r e , l-s Soluble anode e l e c t r o l y s e s of m o l y b d e n u m d i o x i d e - c a r b o n 4 and m o l y s u l f i d e - c a r b o n5 in a KC1KsMoC16 e l e c t r o l y t e o p e r a t e d under an i n e r t a t m o s p h e r e have been r e p o r t e d f r o m this l a b o r a t o r y . Molybdic oxide is a m o r e c o m m o n l y a v a i l a b l e f o r m than m o l y b d e n u m dioxide. Among the sulfide f o r m s of molybdenum, molybdenum s e s q u i s u l f i d e is an excellent e l e c t r i c a l conductor. F r o m these c o n s i d e r a t i o n s , m o l y b d e n u m e x t r a c t i o n f r o m these i n t e r m e d i a t e s , a p p e a r e d to hold some a t t r a c t i o n s . Molybdic o x i d e - g r a p h i t e , molybdenum s e s q u i s u l f i d e graphite and m o l y b d e n u m s e s q u i s u l f i d e without g r a p h ite were investigated, as cell feeds for e l e c t r o d e p o s i tion of high p u r i t y m o l y b d e n u m in a KCI-KsMoC16 e l e c trolyte. EXPERIMENTAL
M a t e r i a l s and Equipment Molybdic oxide and m o l y b d e n u m sesquisulfide for use as cell c h a r g e s were p r e p a r e d f r o m a technical grade molysulfide c o n c e n t r a t e f r o m M / s Climax Molybdenum Company, USA (analysis f u r n i s h e d i
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