Physical Peeling of Passivating Layers on Chalcopyrite Leached with Ferric Ion Using Small Alumina Balls

Abstract

Chalcopyrite is the most abundant copper mineral but notorious as its slow dissolution kinetics in hydrometallurgical processes due to the formation of passivating layers on the surface of the mineral. We tried to improve chalcopyrite leaching rate through adding small alumina balls in a shaking flask to peel off physically the passivating layers. Leaching experiments were carried out in shaking flasks at 333 K in anaerobic condition. Each flask contained ferric sulfate solution (pH 0.7), chalcopyrite concentrate, and alumina balls (5-mm diameter). The effects of the alumina ball addition on the chalcopyrite leaching were outstanding. About 97 % copper dissolution was achieved after 30 hours leaching period, while only 12 % of copper was dissolved from the control experiment. In former case, elemental sulfur was detected clearly as a reaction product. These facts indicate that elemental sulfur formed by ferric leaching did not obstruct copper dissolution in case of alumina ball addition in leaching system. Our findings show that the passivating layers on chalcopyrite surface can be peeled off effectively by physical method and high copper extraction can be achieved.