Efficient Vanadium Extraction from Vanadium Slag by Roasting-Free Assisted Acid Leaching: Pure Oxygen Oxidation of Molten Vanadium Slag

A method of roasting-free vanadium recovery from molten vanadium slag via pure oxygen oxidation-assisted acid leaching was investigated in order to implement efficient and green vanadium recovery. The oxidation process of molten vanadium slag discharged from converters by pure oxygen was simulated, and the phase evolution mechanism of pure oxygen vanadium oxide slag (POOVS) was analyzed. The law between phase evolution and the vanadium recovery rate was systematically expounded. According to the results, POOVS is a Fe₂O₃–V₂O₅–Mn₂O₃–TiO₂–Cr₂O₃–SiO₂ system, and 80.49 to 86.05 pct of vanadium is V⁵⁺. The vanadium leaching efficiency of POOVS reached 97.23 pct. In the range of CaO addition, with the increase of the CaO/V₂O₅ ratio, the vanadium-rich phase in POOVS changed from V₂O₅ and Mn₂V₂O₇ to xCaO–V₂O₅, and the leaching efficiency of vanadium was improved. Under the guidance of response surface methodology, the optimal leaching process parameters were a leaching temperature of 70 °C, a leaching time of 1.63 hours, a H₂SO₄ concentration of 25 pct, and a solid–liquid ratio of 0.09 g/mL. The roasting-free pretreatment method of vanadium slag proposed in this paper uses the waste heat and reaction heat of vanadium slag to complete the mineral phase evolution, which is a green and efficient vanadium extraction technology.