The sonochemical leaching of Chalcopyrite

A fundamental study of the sonochemical leaching of chalcopyrite in ferric ion media has been performed to understand and quantify the effects of sonication and other parameters on leaching reactions. The study covers sulfate and chloride media. The main leaching reaction: CuFeS₂ (s) + 4Fe₃ + (aq) -> Cu₂ + (aq) + 5Fe₂ + (aq) + 2S (s) was found to be dependent on temperature and initial particle size, but less dependent on ferric ion concentration. Leaching kinetics were not affected by ferrous ion concentration or the amount of chalcopyrite added. Leaching was performed under a variety of sonication, thermodynamic and physical parameters. Reaction stoichiometry was confirmed through detailed wet chemistry analysis and mass balance calculations. The use of ultrasound activation showed a clear improvement in leaching kinetics and amount of copper extracted. Sonication has a catalytic-like effect on the leaching reaction. Compared to experiments without sonication, reaction rates were 2-3 times faster at the same temperature and can be faster by a factor of 20 for the same initial particle size. Regardless of initial particle size, the amount of copper extracted is comparable under sonication, and can be twice that under chemical leaching, implying the avoidance of fine particle grinding. Sonochemical leaching was found to be only temperature dependent, where the best copper extraction was at 75 °C. Leaching was further enhanced by the use of a grinding aid. The leaching behavior of chalcopyrite particles remained identical with and without ultrasound activation, implying that the known passivation mechanism in oxidative leaching was not eradicated, as evident from SEM and surface analysis techniques. Sonication did not contribute to particle passivation, as affirmed from different leaching procedures and sonication in aqueous and organic media. Parabolic leaching kinetics were established and confirmed from the estimation of different thermodynamic parameters and dependence on other physical parameters. The developed leaching models from this study are: For pure chalcopyrite: Sulfate media:Applied Science, Faculty ofMaterials Engineering, Department ofGraduat