Giuseppe Granata

Abstract:

Efficient leaching of chalcopyrite concentrates at ambient pressure still remains a challenge because of the low extracting yields and slow dissolution kinetics due to the passivation of the solid surface. In this work, we investigated the generation process of surface species during the leaching of chalcopyrite. Leaching was carried out for up to 24 hours by using 1 mol/L H2SO4 plus Fe3+ as oxidizing agent. The influence of temperature (25, 50, 70A°C) and solution potential (600mV, 700mV) on leaching rate and composition of surface species was investigated by ICP/AES and XPS. Results showed that leaching of chalcopyrite takes place by a first quick dissolution of Fe-O-OH and CuSO4 from the solid surface and then by a slower dissolution of CuS2, which then gradually leaves the surface to CuFeS2. As the leaching proceeds, the formed CuFeS2 undergoes passivation, resulting into the surface product Cu0.34Fe0.20S2, which acts though as an obstacle to the further dissolution of copper, i.e. passivation, thus arresting the leaching. The leaching rate of Cu increased by increasing the temperature but it decreased by increasing solution potential whilst no differences were observed as composition of surface species.