Oxidation of sulfide mineral and metal extraction analysis in the microwave-assisted roasting pretreatment of refractory gold ore

Abstract

The recovery of gold from refractory ore could guarantee sustainable development in the gold industry. However, there are many challenges in the treatment of ore, such as environmental pollution and low recovery. In this regard, the current research focuses on the pretreatment of refractory gold ore and investigates the effect of microwave power, the role of additives, and water on the oxidation and decomposition of sulfide minerals. Pretreatment using microwave-assisted roasting with NaClO3 as an additive to the oxidizing agent is a new method of processing refractory gold ore. Oxidation was studied through sulfur and chlorine mass balance analysis and the degree of metal extraction from sulfide minerals. SEM analysis was carried out to complete the study of the phase change of compounds in the oxidation of mineral sulfides. Roasting of refractory gold ore with a composition of 180 kg NaClO3 and 180 kg water/ton ore reached a temperature of 470 °C at a microwave power of 400 watts for 30 minutes. Total oxidized sulfur reached 90.6%, while only 10.4 % of the sulfur was released, and chlorine release was 49.5%. In addition, water leaching was conducted to investigate the extraction rate of metals after roasting. The results showed that the water leaching extraction of Cu, Zn, Pb, and Fe reached 84.3%, 97.6%, 22.8%, and 8.4%, respectively. Applying microwaves with appropriate concentrations of additives and water resulted in high oxidation of sulfide minerals (>90%) and low sulfur emissions in roasting refractory gold ore with relatively low power, temperature, and time. Moreover, leaching this roasted gold ore resulted in gold extraction of 92.5%; however, leaching of refractory gold without pretreatment resulted in gold extraction of only 47.5%.