Electrolytic reduction of V₃S₄ in molten CaCl₂

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Metallic vanadium was successfully produced starting from vanadium sulfide by applying electrolysis in molten CaCl₂. Vanadium sulfide filled in a cathodic Ti basket and a graphite anode were immersed in the melt of CaCl₂-CaS at 1173 K in Ar, and the electrolysis was conducted at a cell voltage of 3.0 V. Sulfide electrolysis did not form carbon deposit and was free from carbon contamination, while carbon powder was formed on the cathode in the oxide electrolysis using the melt of CaCl₂-CaO. When the CaS content in the molten CaCl₂ increased, electrolysis current increased resulting in fast smelting while the oxygen and sulfur contents in metallic vanadium increased. Oxygen and sulfur contents as low as 3390 ppm and 210 ppm, respectively, were achieved by supplying about four times more electrical charge than stoichiometry.