Abstract
Copper is critically important to industry due to its high electrical and thermal conductivity. The decline in ore grades has led to the search for modern and innovative approaches to extract copper from low-grade ores. Chalcopyrite (CuFeS2) is a copper sulphide mineral and is the primary source of copper in global production. Pyrometallurgical and hydrometallurgical routes are the two main processes used to extract copper from the low-grade sulphide ores. Hydrometallurgy is more desirable due to environmental drivers such as lower energy demand and less gas emissions. However, the lengthy processing times and lower recoveries make it economically unfavorable at the pilot and industrial scales. Microwave heating is of interest due to its potential to improve extraction efficiency, reduce energy and processing costs, and enhance overall sustainability. This study evaluates the interaction of a copper sulphide ore with microwaves, and its implications for comminution, mineral liberation, and downstream leaching. Optical microscope and scanning electron microscope (SEM) micrographs were taken before and after microwave pretreatment, as well as after leaching. The microstructural analysis revealed rapid absorption of microwave energy by the copper sulphide ore, resulting in the formation of extensive micro- and macrocracks throughout the particles. X-ray diffraction (XRD) and thermogravimetric analysis /differential thermal analysis (TGA/DTA) studies were performed to further investigate the heating mechanisms within the minerals during microwave pretreatment. Furthermore, oxidative leaching of the reference (as-received) and microwave treated ores were performed to evaluate the effect of microwave pretreatment on leaching. The leaching results demonstrated that incorporating a microwave pretreatment step prior to crushing and grinding increased copper extraction recovery from 64% to 94%. The kinetics of the leaching process were studied, and the mechanisms leading to improved recoveries were investigated. Finally, a comparison of energy consumption and copper extraction economics, with and without microwave pretreatment was conducted to assess the technoeconomic implications.