Anodic dissolution of n-type and p-type chalcopyrite

Abstract

The anodic dissolution of n- and p-type chalcopyrite (CuFeS₂) was studied in both acidic sulphate and acidic chloride media under conditions relevant to chemical leaching, i.e., at temperatures >70° C and over the potential region 0.2–0.6 V versus SCE. Double potential pulse chronoamperometry was used to probe the surface of the chalcopyrite anodes to determine the activation currents at various applied overpotentials. Analysis of the data obtained in both systems indicated the formation of a surface layer, a solid electrolyte interphase (SEI), which slows the rate of electron transfer. The electron transfer between various redox couples, including Cu²⁺/Cu²⁺, Fe²⁺/Fe²⁺ and I ⁻₃ /I⁻ on n- and p-type chalcopyrite and on Pt, was compared using cyclic voltammetry. In the potential region of interest, the Fe²⁺/Fe²⁺ couple is much less reversible on chalcopyrite than are the Cu²⁺/Cu²⁺ and I ⁻₃ /I⁻ redox couples. Chemical leaching of chalcopyrite in the presence of various oxidants was also carried out, and the results of the chemical experiments were discussed in terms of the electrochemical properties of the systems.