Thermal decomposition behavior of pyrite in a microwave field and feasibility of gold leaching with generated elemental sulfur from the decomposition of gold-bearing sulfides

The flue gases produced in the oxidation roasting process of gold concentrates contain numerous poisonous oxides which limit the widespread industrial application of this pretreatment method. In this study, the effect of microwave pretreatment on the decomposition behavior of pyrite was investigated in an inert atmosphere using a response surface methodology. Additionally, the feasibility of gold leaching with generated elemental sulfur from the decomposition of gold-bearing sulfides was confirmed. Results showed that microwave power and irradiation time had significant influences on the thermal decomposition of pyrite, and that there was a significant interaction effect between these two variables. The Au extraction achieved based on the alkaline sulfide leaching of gold with generated elemental sulfur after microwave pretreatment was 91.98%, which indicated that this leaching method can efficiently extract gold from the sulfide concentrates. X-ray diffraction (XRD) images provided direct experimental evidence that pyrite (FeS2) was decomposed into elemental sulfur and pyrrhotite (Fe1-xS) following microwave heating in an inert atmosphere. Microstructural changes and elemental distribution revealed that microporous structures formed in microwave pretreatment could effectively liberate encapsulated gold and facilitate the gold leaching process. Overall, this study presents collective information for gold extraction from gold-bearing sulfides based on a leaching process consisting of microwave pretreatment in an inert atmosphere, and sequential alkaline sulfide leaching of gold with the generated elemental sulfur from the decomposition of sulfide concentrates.