The interaction of Ag+ with synthetic chalcopyrite in the presence of Fe3+ and Cu2+ in sulfuric acid solutions

Abstract

Silver (Ag+) and cupric (Cu2+) ions are known to be catalysts for oxidation of chalcopyrite (CuFeS2) in acid solutions. The present study investigates the interaction between Ag+ and Cu2+ with synthetic chalcopyrite under oxidative conditions in acidic ferric (50 mM Fe3+) sulfate solutions. After addition of Ag+ (e.g. concentration 20 mg/L) to solutions containing Cu2+, the oxidation rate of chalcopyrite increased from 1.08 × 10−6 to 12.65 × 10−6 A/cm2. In contrast, addition of 5 and 50 mM Cu2+ to solutions containing Ag+ decreased the chalcopyrite oxidation rate from 20.79 × 10−6 to 12.65 × 10−6 and 19.50 × 10−6 A/cm2, respectively. Oxidative chalcopyrite leaching tests results were in good agreement with those of the electrochemical tests above. X-ray photoelectron spectroscopy showed higher insensitivity of Ag 3d in leaching residue containing Cu2+ than residue without Cu2+. S 2p spectra analysis indicated the highest percentage of the disulfide form when leached in the Fe3+-Cu2+-Ag+ system, which suggests a synergistic effect of Cu2+ and Ag+ in the conversion of monosulfide to disulfide in chalcopyrite.