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• The electrochemical behavior of molybdenum ions and their electrodeposition mechanism in molten salts were systematically investigated. • The variation of Mo element concentration and the valence state of the molten salt bottom product was tested by in situ salt extraction during electrolysis. • The causes of current fluctuation during constant voltage electrolysis were revealed, culminating in the successful electrolysis of molybdenum. The electrochemical behaviors of molybdenum ions in NaCl-KCl molten salt at 750 °C were studied in detail, and pure metallic molybdenum was collected on the cathode. The reduction and diffusion processes of molybdenum ions in NaCl-KCl molten salt were also identified using cyclic voltammetry and square wave voltammetry. The diffusion coefficient and nucleation mode of molybdenum ions were analyzed. Electrodeposition was performed at a constant voltage and the variation of current with time was recorded. The variation of Mo element concentration and the valence state of the molten salt bottom product was tested by in situ salt extraction during electrolysis. The result demonstrated that the electrode reduction process of molybdenum ion in NaCl-KCl molten salt at 750 °C was a two-step reaction, Mo(V) → Mo(III) → Mo, all of which was reversible and controlled by diffusion. Meanwhile, the nucleation mode of molybdenum ions was found to be progressive nucleation. It was determined by XRD, SEM and EDS that the primary component of the cathode deposition product was molybdenum. [ABSTRACT FROM AUTHOR]

• It is a novel process for the separation and preparation of molybdenum and zinc from MoS 2 and ZnS in magnetic separation tailings. • The electrochemical behaviors of MoS 2 , ZnS and MoS 2 -ZnS was investigated in detail, and the mechanism of desulfurization of MoS 2 -ZnS was proposed. • Zn/ZnS played a role of a reducing agent in the process of MoS 2 -ZnS co-desulfurization, which facilitated the process of desulfurization and the semiproduct of zinc could be reused. • It enabled the reduction of MoS 2 at a lower voltage while ZnS presenting in the desulfurization process. 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. [ABSTRACT FROM AUTHOR]

A review emphasized on the electro-desulfurization mechanism of sulfides as cathodes or anodes in molten salts. [Display omitted] • The research advance of metal or alloy prepared by molten salt electro-desulfurization is reviewed for the first time in this paper. • This review provides a comprehensive insight into the electrode reaction mechanism of various metal sulphides in molten salts. • The challenges in molten salt electro-desulfurization technology are summarized and the future research direction is pointed out. Sulfide is one of the most abundant minerals in the earth's crust and a major raw material for metal extraction. The traditional pyrometallurgy or hydrometallurgy process is relatively lengthy, and will produce CO 2 and SO 2 with greater hazards for environment. Electro-desulfurization is a metal extraction method developed in the past 20 to 30 years, which is considered to be an environmentally friendly and simple process. In electro-desulfurization process, sulfide is used as electrode and raw material, and molten salt is used as electrolyte. Metal and elemental sulfur are extracted at the cathode and anode respectively after current is introduced, meanwhile CO 2 and SO 2 are not produced. In this paper, the recent research of electro-desulfurization in molten salts is summarized, including the electrode reaction process when sulfide is used as cathode or anode, electrolytic products and factors affecting current efficiency and energy consumption. It is expected to provide suggestions for future direction and enhance the theoretical support for the clean development of sulfides through the comprehensive analysis of molten salt electro-desulfurization process. [ABSTRACT FROM AUTHOR]