Reduction mechanism and optimization of prepare metallic antimony through direct microwave carbothermal reduction of antimony oxide concentrate

In this work, a clean microwave carbothermal reduction of Sb2O3 mineral to prepare metallic antimony ingot is proposed. Response surface methodology was used to optimize condition for microwave carbothermal reduction of Sb2O3. The roasting temperature, roasting duration, carbon powder ratio and NaCl addition ratio was collected to carry out a four-factor and three-level experiment. In the optimized conditions, a >77.0% yield of antimony ingot can be obtained under roasting temperature of 730 °C, roasting time of 60min, carbon powder ratio of 0.3, NaCl addition amount of 4%. More than 99% Sb content of metallic Sb ingot is obtained in the microwave field. The mechanism of microwave carbothermal reduction of Sb2O3 was investigated by XRD, SEM-EDS and Mapping analysis, the results show that the microwave reduction process is divided into three stages based on the melting point of antimony, namely, 25 °C–400 °C, 400 °C–630 °C, and above 630 °C, which differ in terms of phase transformation. In the microwave field, the reduction of Sb2O3 to Sb particles can be completed within 15 min. Microwave metallurgical technology is conducive to the sustainable development of antimony metallurgy, and also provides a clean technology for the metallurgy industry.