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Abstract

Chalcopyrite (CuFeS₂) is the dominant economic mineral source for copper. This metallic sulfide is a semiconductor and can be activated by light. We investigated the photocatalytic leaching of chalcopyrite under two oxidative conditions in ferric ion-containing sulfuric acid and in aerated sulfuric acid. This investigation exploits both visible and ultraviolet (UV) region wavelength to enhance chalcopyrite leaching at atmospheric pressure. Copper leaching extraction curves were determined in sulfide mineral suspensions from both synthetic and concentrate chalcopyrite sources. The chalcopyrite dissolution has been examined from an integrated point of view where the hydrometallurgical leaching parameters (i.e. lixiviant concentration, temperature and pulp density) and typical photoelectrochemical behaviour are discussed together. We found temperature promotes photon excitation. A thermodynamic relation was derived to address the Gibbs free energy of light with the Nernst equation for the current oxidative systems. By fitting with the shrinking core model, we found the reactions are surface chemical reaction limited and there exists an Arrhenius-type equation for light. In contrast to the established view of “lower pH is better” for proton attack and leaching, there is an optimal range of H⁺, since it competes with the dissolved Fe³⁺, Cu²⁺, cations based on the surface charge. Considerably higher pulp density yielded higher copper extraction, but it also hinders the photocatalytic effect due to the current experimental setup. TiO₂ added to a CuFeS₂ suspension was found to catalyze chalcopyrite degradation. This research marks one of the first instances of light utilization within the traditional ferric sulphate leaching system for chalcopyrite under atmospheric conditions, with special emphasis on photoelectrochemical theory rather than passivity.