The kinetics of oxidative leaching of vanadium trioxide

• Oxidative leaching of vanadium(III) is studied using oxygen and Fe(III)/Fe(II).
• Atmospheric oxidative leaching of vanadium(III) using oxygen is slow.
• Fe(III) can increase kinetics of vanadium(III) leaching significantly.
• The oxidation rate was proportional to the Fe(III)/Fe(II) to the power of 0.47.

The oxidative leaching of vanadium trioxide was studied in sulfuric acid solutions from 30 °C to 90 °C. This study was performed in three stages. First, the kinetics of leaching using oxygen was investigated. It was shown that this oxidative leaching is chemically-controlled with an activation energy of around 69 kJ/mol. Secondly, vanadium(III) oxidative leaching was studied using ferric ions and oxygen. The presence of ferric enhanced kinetics significantly. Finally, oxidative leaching using a constant ferric–ferrous ratio from 1 to 300 was investigated. Potassium permanganate (KMnO4) was found to be a suitable oxidant for controlling solution potential. The oxidation rate using a constant ferric–ferrous ratio was very sensitive to temperature, giving a large activation energy (38 kJ/mol) and was proportional to the Fe(III)/Fe(II) ratio to the power of 0.47. The leaching rate using the shrinking sphere model was modeled as:∂d∂t=12,088×exp−4580TCFeIIICFeII0.47μmmin.