Elemental Sulphur Formation During the Ferric Sulphate Leaching of Chalcopyrite

Abstract

Abstract The formation of elemental sulphur during the ferric sulphate leaching of chalcopyrite at 95°C has been elucidated. About 94% So formation, and less than 6% SO4 generation, is observed regardless of the leaching time (0–70 h), the Fe2(SO4)3 concentration (0–2 M Fe3+) and the chalcopyrite particle size. Furthermore, the relative amounts of Soand SO4do not vary systematically with any of the above variables. The leaching of extensive polished chalcopyrite surfaces (∼1 cm2) results in the formation of discrete globules of So on a roughened chalcopyrite surface. By contrast, chalcopyrite grains <40 μm quickly become enveloped in a compact layer of elemental sulphur which is likely sufficiently protective to be responsible for the observed non-linear leaching kinetics. Continuation of the leaching process results in the progressive thickening of the sulphur layer and the agglomeration of the individual chalcopyrite particles into larger masses via the sulphur.