Electrochemical oxidation of chalcopyrite (CuFeS₂) and the related metal-enriched derivatives Cu₄Fe₅S₈, Cu₉Fe₉S₁₆, and Cu₉ Fe₈S₁₆

The electrochemical oxidation of chalcopyrite and its metal-enriched derivatives, haycockite, mooihoekite and talnakhite have been investigated using electrochemical techniques and X-ray photoelectron spectroscopy. The results show that when chalcopyrite, haycockite, mooihoekite, and talnakhite are oxidized in 1 M HClO₄ in the electrode potential region of 0.2-0.6 V vs. S.C.E. at 298 K, the oxidation products are Cu_xS_z*, Fe²⁺ and, at electrode potentials > 0.53 V vs. S.C.E., Fe³⁺ ions; Cu_xS_z* represents a metastable phase at the electrode surface. The relative rates of oxidation are in the order haycockite > mooihoekite > talnakhite > chalcopyrite. When chalcopyrite, haycockite, mooihoekite, and talnakhite are oxidized in 0.3 M NaCl + HCl solution of pH 0.1, the oxidation rates remain essentially in the order haycockite > mooihoekite > talnakhite > chalcopyrite. -from Authors