Oxidative Leaching Kinetics of Vanadium from the Vanadium-Chromium-Reducing Residue with K₂Cr₂O₇

Oxidative-alkaline leaching of vanadium from vanadium-chromium-reducing residues with K₂Cr₂O₇ was investigated in this paper. The effects of processing parameters including dosage of NaOH, dosage of K₂Cr₂O₇, reaction time, and reaction temperature on the leaching efficiency of vanadium were studied. The results simulated by response surface methodology indicated that vanadium leaching was affected significantly by the dosage of K₂Cr₂O₇ and NaOH, and the processing parameters that affected the leaching efficiency of vanadium followed the order m(NaOH)/m(residue) > m(K₂Cr₂O₇)/sssssm(residue) > reaction temperature > reaction time. The leaching efficiency of vanadium was up to 99.92% under optimal conditions: reaction temperature of 90 °C, reaction time of 60 min, liquid-to-solid ratio of 5:1 mL g^-1, m(K₂Cr₂O₇)/m(residue) = 0.10, and m(NaOH)/m(residue) = 0.30. The kinetics analysis indicated that diffusion through the product layer was the controlling step and the apparent activation energy for vanadium leaching was calculated to be 58.275 kJ·mol^-1.