The effect of microwave pretreatment on the liberation and flotation of a copper–molybdenum porphyry ore

Microwave pretreatment prior to comminution has been shown to provide numerous benefits, including reduced ore competency, enhanced mineral liberation, and increased metal recoveries in downstream processes such as flotation. In the current research, the benefits of microwave pretreatment of a copper–molybdenum porphyry ore were investigated at the bench scale. Firstly, the permittivities of the ore were measured as a function of temperature and frequency, with Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC) being performed in order to assist in the interpretation of the results. Secondly, microwave heating behaviour studies were conducted, providing insight into the microwave amenability of the ore. Thirdly, using Quantitative Evaluation of Minerals by Scanning Electron Microscopy (QEMSCAN), the degree of mineral liberation after microwave treatment was evaluated by comparing the microwave-treated samples with the reference untreated samples. Fourthly, flotation studies were conducted to determine the effect of microwave pretreatment on the flotation kinetics, as well as the recoveries and grades of both copper and molybdenum in the concentrate. The results demonstrate that microwave pretreatment enhances mineral liberation and selectively improves molybdenum flotation performance, increasing molybdenum recovery from 47.3 % to 56.5 % at a grind size of 200 µm and from 37.2 % to 63.9 % at 250 µm, while the copper recovery remains largely unchanged. Finally, some comments are provided regarding the applicability of microwave pretreatment for copper–molybdenum porphyry ores.