Abstract:Vanadium and molybdenum in V-Cr waste residue were leached in sulfuric acid with addition of sodium sulfite. Effects of amount of sodium sulfite, leaching temperature, volume concentration of sulfuric acid, and leaching time on leaching rate of vanadium and molybdenum were systematically studied. The results show that vanadium leaching rate is 94.55% (11.84 percent point improvement compared with no addition of sodium sulfite), molybdenum leaching rate is 90.46%, meanwhile, and leaching rate of other metal elements such as chromium or iron are below 5% under the optimum conditions including sodium sulfite dosage of 20%, leaching temperature of 25 ℃, volume concentration of sulfuric acid of 12%, and leaching time of 2 h. According to XRD and thermodynamic analyses, addition of sodium sulfite significantly reduces ΔG of vanadium dissolution reaction, promotes reductive leaching of calcium vanadate and raises vanadium leaching rate. The easily dissolved properties of calcium molybdate in acid solution does not affected, while chromium trioxide and impurity element iron which exist in crystal lattice of chromium trioxide are difficult to dissolve due to stable structure.