Influence of microwave pretreatment on the bioleaching behaviour of low-grade complex sulphide ores

Mineralogical information on the mechanisms by which microwave pretreatment improves the bioleaching behaviour of low-grade complex sulphide ore, and an interpretation of the interrelationship between mineralogy, microwave processing, and bioleaching process are provided in this study. The influence of microwave irradiation on the bioleaching behaviour and mechanisms of a low-grade complex sulphide ore subjected to microwave heating in a kitchen type microwave oven at a power output 1100 W for 5 min was investigated in a mixed mesophilic bacterial culture through bioleaching experiments and electrochemical techniques. Results revealed that microwave treatment improved the bioleaching of behaviour of the ore, with more effect on copper and iron dissolutions than on zinc and lead. Both microwave treated and untreated samples showed similar electrochemical behaviour. However, microwaved samples displayed higher reactivity, dissolution rates, dissolution currents, current densities and a decreased polarization resistance. Increase in dissolution of the microwaved treated samples resulted from phase changes in the ore which promoted galvanic interaction within the system, decrease in the amounts of sulphur contents, and an increase in electrochemical sites resulting from an increase in the number of cracks induced by microwave heating.