An X-ray photoelectron spectroscopic study of the oxidation of chalcopyrite

Abstract

The oxidation of fracture surfaces of chalcopyrite has been investigated by means of X-ray photoelectron spectroscopy. Exposure of chalcopyrite to air resulted in iron becoming concentrated at the surface of the mineral to form an iron hydroxy-oxide. The sulfur spectrum of an oxidized surface, determined at 150 or 295 K, displayed new intensity at the high binding energy side of the peak arising from unaltered chalcopyrite. This is interpreted in terms of the formation of a sulfur-rich copper sulfide of stoichiometry CuS₂. Extended exposure to air resulted in the formation of sulfate and copper(II). The products of oxidation of chalcopyrite in air-saturated ammonia solution were the same as those observed during exposure to air. Iron and some copper were dissolved in the oxidation in acid media and the resultant surface layer had a composition near Cu_0.8S₂ Reaction of an acid-leached surface with hydrogen peroxide produced elemental sulfur in addition to a metal deficient copper sulfide.