The role of zinc sulfide in the electrochemical extraction of molybdenum
Huakui Zhang, Shaolong Li, Zepeng Lv, Jilin He, Yong Fan, Jianxun Song
Abstract
The main form of molybdenum in nature is molybdenum sulfide. It also exists in iron ore magnetic separation tailings together with zinc sulfide. Considering separating and extracting molybdenum and zinc, a large amount of SO 2 is released and environmental pollution is caused by high energy consumption for the traditional pyrometallurgy process. This research proposes a novel process to achieve efficient extraction and separation of molybdenum and zinc through co-desulfurization of MoS 2 -ZnS in molten salt. It was found that the sulfur in MoS 2 and ZnS could be effectively removed and collected as solid sulfur by constant potential electrolysis in molten NaCl-KCl at 750 °C. Furthermore, electrochemical testing showed that the decomposition of MoS 2 was carried out in two steps, ZnS was reduced in one step, and the decomposition voltage of ZnS was smaller than that of MoS 2 . Zinc was obtained at the first stage, and the MoS 2 or its intermediate compounds were wrapped around by liquid zinc. The substitution reaction, 2Zn + MoS 2 = Mo + 2ZnS, was able to promote the decomposition of MoS 2 in the electrolysis process. Zinc sulfide was then formed in the second stage, and it can be electrolyzed to metallic zinc again for reduction of MoS 2 . Zn/ZnS played the role of a reducing agent in the process of MoS 2 -ZnS co-desulfurization, which facilitated the process of desulfurization, and enabled the reduction of MoS 2 at a smaller voltage while zinc could be reused. In this work, molybdenum metal containing zinc was extracted at a cell voltage of 2.7 V. Metallic zinc and molybdenum were separated and purified in the final stage by vacuum distillation.