Solvent extraction of uranium from dilute solutions using a gas-bubble mixed extraction column
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A f t e r m i x i n g , the i m m i s c i b l e p h a s e s a r e s e p a r a t e d , the m e t a l v a l u e s a r e s t r i p p e d f r o m the o r g a n i c with an aqueous s t r i p p i n g solution, and the m e t a l i s then r e c o v e r e d by an a p p r o p r i a t e technique, c o m m o n p r a c t i c e being p r e c i p i t a t i o n . One of the c r i t i c a l o p e r a t i o n s in the o v e r a l l s o l v e n t e x t r a c t i o n p r o c e s s is the m i x i n g of the o r g a n i c and aqueous p h a s e s . The n a t u r e of this m i x i n g i s i m p o r t a n t to the s u c c e s s of the p r o c e s s s i n c e it affects f i r s t , the r a t e of t r a n s f e r of u r a n i u m to the o r g a n i c and thus the r e c o v e r y , and secondly, the a m o u n t of o r g a n i c l o s s by e n t r a i n m e n t in the aqueous p h a s e . Conventional solvent extraction processing utilizes m i x e r - s e t t l e r u n i t s to a c h i e v e m i x i n g of the a q u e o u s and o r g a n i c p h a s e s . U s e of m i x e r - s e t t l e r s p e r m i t s continuous t r e a t m e n t of feed, but the p r o c e s s i n g r a t e i s r e s t r i c t e d by the t i m e r e q u i r e d for p h a s e s e p a r a tion a f t e r m i x i n g . B e c a u s e of the h i g h - s h e a r type m i x i n g u s e d i n a m i x e r - s e t t l e r a p o r t i o n of the o r ganic p h a s e b e c o m e s m e c h a n i c a l l y e n t r a i n e d in t h e aqueous r e s u l t i n g in loss of e x t r a c t a n t . F o r this R. J. ANDREINI is at the Paul D. Merica Research Laboratory, International Nickel, Inc., Sterling Forest, NY 10901. T. J. DeMULL,Jr., is at the U. O. P. Development Center, Tucson, AZ 87510. G. W. LOWER is Professor, MetallurgicalEngineering Department, Michigan Technological University, Houghton, MI 49931, where R. J. Andreini and T. J. DeMull, Jr., were formerly Graduate Students. Manuscript submitted December 20, 1974. METALLURGICAL TRANSACTIONSB
r e a s o n a p p l i c a t i o n of m i x e r - s e t t l e r u n i t s is often l i m i t e d by the s e t t l i n g a r e a r e q u i r e d for p h a s e s e p a r a tion, e s p e c i a l l y for s y s t e m s w h e r e high v o l u m e t h r o u g h p u t s a r e d e s i r a b l e or n e c e s s a r y . S e v e r a l a l t e r n a t i v e s to m i x e r - s e t t l e r o p e r a t i o n s i n v o l v i n g the u s e of c o l u m n e x t r a c t o r s have b e e n p r o posed. P a c k e d c o l u m n s , 1-2 i n which o r g a n i c and a q u e ous p h a s e s a r e fed c o u n t e r c u r r e n t l y u t i l i z e p a c k i n g m a t e r i a l s s i m i l a r to those u s e d i n gas a b s o r p t i o n or distillation columns. Extraction columns utilizing r o t a t i n g 3-5 or r e c i p r o c a t i n g e l e m e n t s 6-~ to a c h i e v e m i x i n g have a l s o b e e n developed. Van D i j c k 8 o r i g i n a ted p u l s e d c o l u m n s , in which m e c h a n i c a l or a i r p u l s i n g of the p h a s e s e n h a n c e s the m i
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