Optimization and kinetic analysis of direct acid leaching of vanadium from converter vanadium slag under atmospheric pressure

Converter vanadium slag is an important kind of raw material for the production of vanadium products. Not only does the atmospheric acid leaching of vanadium from vanadium slag without roasting avoid the pollution of exhaust gas generated from roasting, but also it reduces the threat of Cr(VI) and V(V) and is conducive to the vanadium products preparation with low valence state. In this paper, the optimization of leaching conditions by response surface methodology and the direct sulfuric acid leaching kinetics of vanadium from converter vanadium slag were investigated. In the consequence of experiments, the optimum atmospheric sulfuric acid direct leaching conditions were initial sulfuric acid concentration of 4 mol/L, reaction temperature of 90 degrees C, reaction duration of 8 h and liquid to solid ratio of 8 mL/g with the particle size of vanadium slag below 20 mu m. Under the optimum conditions, the vanadium leaching efficiency was 86.09%. The kinetics analysis demonstrated both the chemical reaction and inner diffusion were the control steps of the leaching process. The calculated apparent activation energy of the leaching process was 17.63 kJ/mol and the reaction order of sulfuric acid was 0.78.