Electrocrystallization of copper in chloride aqueous solutions
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and they considered that the other main difficulties a r e due to the high temperature needed for the leaching process (90°C) and t o oxidation of the electrolyte coming in contact with air. Recently, interest by industry for copper electrowinning out of chloride solutions was shown by the Cymet P r o c e s s5 which aims at producing a copper powder from sulfide concentrates, and by Atwood and Curtis 6 who proposed t o l e a c h a chalcopyrite concentrate with a f e r r i c chloride solution, to r e d u c e the cupric chloride solution by m e a n s of copper powder, and finally to electrolyze the cuprous chloride solution. Again, problems a r i s e concerning the quality of the cathodic deposits (structure and purity), the high temperature needed for the leaching process, and the oxidation of the electrolyte after its r e d u c tion with copper powder. Mussler, Olsen and Campbell, 7 in an attempt to electrowin copper from chloride solutions, also point out that this type of electrolyte favors the production of powders r a t h e r than plates. However, at the 105th AIME Annual Meeting, where the present paper was delivered, Cathro8 showed a dense cathodic deposit obtained with a cuprous chloride electrolyte containing 2 g/1 gelatine. Although the present paper is essentially devoted to electrowinning, w e should not overlook the work of a number of r e s e a r c h e r s in the field of electrorefining. 9-12 The main difficulties encountered here were due t o the behavior of impurities such as arsenic, antimony and bismuth which contaminate the cathodic deposit. It is interesting t o note that the electrolytic conditions are sometimes quite different from those suggested for electrowinning: h e r e , current densities as high as 500 A//m2 and temperatures between 50 and 75°C are used, but some glue is added t o improve the smoothness of the deposits. Nevertheless, we may conclude from this short survey of the literature that additional experimental work is needed in o r d e r to gain more p r e c i s e information on the structure of the deposits under different conditions. F i r s t of all, a pure chloride solution should be used at different temperatures, current densities and durations. After this b a s i c study has been completed, the addition of inhibitors and impurities t o the solution might be investigated. The present paper deals with the f i r s t part of VOLUME 8B, JUNE 1977-315
current lead
this g e n e r a l program, and the results of the investigation will be interpreted in t e r m s of the g e n e r a l considerations on the structure of electrolytic deposits previously published by one of the authors .13
slit
EXPERIMENTAL Fig. 1 is a schematic representation of the whole apparatus,14 while Fig. 2 is a more detailed drawing of the electrolytic cell. The CuC1 solution is fed in b o t h cathodic and anodic compartments of the diaphragm c e l l . At the copper cathode, cuprous ions are reduced: Cu*
+
e
~
Cu
whereas at the anode, the same ions are oxidized: Cu ÷ - Cu++ + e. The sol
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