Selective separation and utilization of valuable metals from vanadium slag for the preparation of VOSO₄ electrolyte

The traditional processing methods of vanadium slag have been narrowly focused on the extraction of vanadium, resulting in a significant squandering of resources and environmental pollution of V(V) and Cr(VI). Addressing this, this study investigates the separation and comprehensive utilization of Fe(II), Mn(II), Cr(III), Ti(IV), and V(IV) in vanadium slag. Low temperature sulfate roasting was applied to prepare low valence multiple metals solution from vanadium slag, it avoids the formation of toxic V(V) and Cr(VI) compounds. Impurities, Fe(II) and Mn(II) ions, was separated by oxalic acid precipitation method, and the FeC₂O₄·2H₂O and MnC₂O₄·2H₂O precipitates were further manufactured to be lithium iron manganese phosphate (LiFe_0.5Mn_0.5PO₄@C) cathode materials. Cr(III) impurity was complex separated and converted to Cr₂O₃ product with a purity of 97 %. Finally, a high-purity VOSO₄ solution with a concentration of 80 g/L was obtained, with vanadium concentration and impurity elements content meet the Chinese national standard for vanadium battery electrolytes. The process consumes 593 kWh of energy to process 1000 kg/h of vanadium slag and achieves comprehensive utilization of valuable metals.