Decopperizing lead with sulfur. influence of deficient sulfides
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5. J. Kramss, M. G. Frohberg, and M. L. Kapoor: Metall., 1971, vol. 25, pp. 1127-30. 6. S. Otsuka and Z. Kozuka: Met. Trans. B, 1975, vol. 6B, pp. 389-94. 7. P. M. Shurygin and V. J. Kryuk: hr. Akad. Nauk SSSR, Met. Gorn. Delo., 1963, pp. 94-95.
2 C_._UU(wt pct in Pb) + S(,) ~ Cu2Sts) AG603 K
Decopperizing Lead with Sulfur. Influence of Deficient Sulfides F. BELIS, W. VEHWIMP, J. R. ROOS O v e r the y e a r s a c o n s i d e r a b l e a m o u n t of r e s e a r c h has been spent on d e c o p p e r i z i n g of lead with s u l f u r . One m a j o r r e a s o n for this is the i n t r i g u i n g d i f f e r e n c e b e t w e e n the r e s u l t s of c o m m e r c i a l p r a c t i c e and p r e d i c t i o n s b a s e d on t h e r m o d y n a m i c c a l c u l a t i o n s . A s a t i s f a c t o r y e x p l a n a t i o n of the m e c h a n i s m of d e c o p p e r i z ing has not yet b e e n given. In a r e c e n t p u b l i c a t i o n Krysko* r e v i e w s the d i f f e r e n t m e c h a n i s m s which have b e e n put forward. G e n e r a l l y , an e q u i l i b r i u m b e t w e e n PbS and Cues has been proposed, a c c o r d i n g to: 2CU(pb) + PbSts) ~-" Cu2Sts) + P b t n .
[1]
As a p p e a r s from t h e r m o d y n a m i c c a l c u l a t i o n s this r e a c t i o n cannot be r e s p o n s i b l e for an e q u i l i b r i u m c o n c e n t r a t i o n lower than 0,047 wt pet. 2 In a n o t h e r group of p u b l i c a t i o n s , the p r e s e n c e of t h i r d e l e m e n t s , like Ag, Sn, Bi, Sb and As was m a d e r e s p o n s i b l e for the low copper contents a t t a i n e d in c o m m e r c i a l p r a c t i c e . However, the s t a t e m e n t s about the effect of these specific i m p u r i t i e s w e r e v e r y often c o n t r a d i c t i n g each other. 2-s On m a n y o c c a s i o n s the r e a c t i o n s c h e m e s p r o p o s e d w e r e highly i n t r i c a t e , including e.g. c o m p l e x d o u b l e sulfides. 6 However, one can think of a n o t h e r , r a t h e r s i m p l e r e a c t i o n m e c h a n i s m which could e x p l a i n the a t t a i n merit of a copper content, even l o w e r than the content a t t a i n e d in c o m m e r c i a l p r a c t i c e . We suppose that, at 330~ S i m m e d i a t e l y m e l t s and r e a c t s as such with the Cu in the lead bullion.
2 Cuts)
+
1/2Sztg) ~ CueSts) AG~r = - 3 4 , 1 5 0 - 6 . 2 2 T l o g T + 28.74T (Kubaschewski) 7
[2]
S--(at. pct in Pb) ~ 1/2S2tg) ZxG~ = 19,300 - 0.6T (Blanks and W i l l i s ) 2
[3]
St,) -~-S_(at" pct in Pb) A
Go600oc
__
- 19,103 [4] (Twidwell and L a r s o n ) 8
2(C__u_U(wtpct in Pb) ~ Cuis))
F. BELIS and W. VERWIMParc Research Assistants, and J. R. ROOS is Professor of Extractive Metallurgy, Department of Metallurgical Engineering, Katholieke Universiteit Leuven, G. de Croylaan 2, B-3030 Heverlee, Belgium. Manuscript submitted July 22, 1975. METALLURGICAL TRANSACTIONS B
= - 3 4 , 0 8 9 cal.
[6]
The AG ~ value for r e a c t i o n [4] is a s s u m e d to be r e a s o n a b l y valid at 3
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