Sulfur fixation and reduction roasting of stibnite for clean extraction of antimony by a combined metallurgy and beneficiation process

Abstract The direct sulfur fixation and reduction roasting of antimony sulfide (Sb2S3) were investigated for antimony extraction, based on the combination of metallurgy and beneficiation. Zinc oxide (ZnO) and carbon, used as the sulfur-fixing agent and reductant, respectively, were roasted with Sb2S3 to form Sb metal and zinc sulfide (ZnS). The products were separated by gravity separation and flotation. The predominance-area diagrams of Sb-Zn-S-O indicated that Sb2S3 could be transformed into Sb directly. The equilibrium composition simulation indicated that sulfur was completely fixed in the form of ZnS. The in-situ X-ray diffraction and TG–MS analysis of the Sb2S3-ZnO-C system indicated that the roasting process was initially conducted as a sulfur-fixing reaction to generate antimony oxide (Sb2O3) and ZnS; thereafter, the Sb2O3 was reduced to metallic antimony. The optimum conditions for Sb2S3 conversion were determined as follows: temperature of 800 °C, carbon particles of 150–200 mesh, WZnO/Wtheory = 1.0 (where W represents weight), and a time period of 2 h, where the Sb generation and sulfur-fixing rate reached 90.44% and 94.86%, respectively. The gravity and flotation separation method generated the recovery rates of 87.32% and 92.04% for Sb and ZnS, respectively. Compared with the current process, this new method will significantly facilitate the reduction of energy cost and SO2 emissions.