An electrochemical study of the carrollite-chalcopyrite system in xanthate and cyanide containing solutions

Abstract

A study has been made of the electrochemical behaviour of carrollite and chalcopyrite in the presence of xanthate and cyanide in aqueous solution. The investigations involved measurements of rest potentials and cyclic voltammetry of the sulphide minerals understudy. The results showed that the measured rest potential depends on among other things, the subsequent stable species on the mineral surfaces. In acid media Co2+ and Cu2+ ions determined the measured rest potentials on the carrollite electrode whilst Co(OH)2 and CU2O were responsible for the potential in alkaline media. Cu2+ and Fe2+ ions determined the measured potential on the chalcopyrite electrode in acidic media whilst Fe(0H)3 and Cuz0 were the potential determining species in alkaline media. The major xanthate oxidation product, dixanthogen was present on the carrollite in sufficient quantities at pH 9.2 but not at pH 7.0 and 11.0. At this pH value the carrollite was rendered hydrophobic. In the presence of cyanide, carrollite was hydrophilic particularly at high values as predicted by the magnitudes of the potentials. In case of chalcopyrite dixanthogen formed only at pH value of 7.0 and 9.2. At pH 11.0 metal xanthate was the major product and was responsible for hydrophobicity even in the presence of cyanide. Thus the role of cyanide as a depressant was to introduce an anodic oxidation reaction which proceeded faster than the xanthate oxidation reaction on both minerals. On the basis of the above electrochemical behaviour an effecient separation between the two minerals appears possible only by precise control of both xanthate and cyanide concentration under carefully optimised conditions.