A Study of Microwave Assisted Leaching of Copper Sulfide Minerals

Abstract

Chalcopyrite is an abundant copper sulfide mineral that is highly refractive to leaching and is usually processed through pyrometallurgy. Given the environmental and economic burden of pyrometallurgy, the hydrometallurgical processing of chalcopyrite has attracted increasing interest. This study has been carried out to investigate the leachability of microwave pretreated chalcopyrite using a novel lixiviant, sodium persulfate (Na2S2O8), as an oxidant in pH=1 H2SO4 solutions. The microwave pretreatment of chalcopyrite was performed under atmospheric conditions at a power level of 900 watts for two minutes. Batch experiments were performed examining the effect of temperature, particle size, and oxidant concentration on the leaching kinetics of microwave pretreated chalcopyrite. Results indicate that temperature and microwave pretreatment drastically increase kinetics. Through optimization of leaching conditions, copper recoveries of up to 74% were observed in microwave pretreated samples compared to 37% in untreated samples. Analysis utilizing SEM/EDS (scanning electron microscopy and energy-dispersive X-ray spectroscopy) revealed that microwave pretreatment results in surface and elemental morphologies that favor the dissolution of chalcopyrite, including thermally induced cracking and the regional concentrating of elements. However, consistent mineralogical changes were not observed. It was determined that copper leaching from microwave pretreated chalcopyrite followed surface reaction rate-limited kinetics, according to the shrinking-core model equation 1-(1-X)1/3. The apparent activation energy was found to be 38.77 kJ/mol.