The leaching of vanadium pentoxide using sulfuric acid and sulfite as a reducing agent

• Solubility of vanadium in sulphuric acid media up to 90 °C is studied.
• V2O5 can be leached at pH=5 as decavanadate in around 2 hours at 90 °C.
• V2O5 can be completely dissolved at pH=8 as metavanadate in about an hour at 90 °C.
• Reductive agents in acidic pH range can increase leaching efficiency significantly.
• Kinetics of reductive leaching is a chemical control regime.

Vanadium has been produced from both primary and secondary sources having various compositions. One of the most available sources of vanadium is vanadium pentoxide. In this paper, vanadium pentoxide leaching was investigated using three chemistries. First, vanadium leaching and the solubility of pentavanadyl ion (VO2+) at different pHs and temperatures were investigated in the sulfuric acid system. It was shown that decreasing pH and temperature as well as increasing sulfate concentration in the solution will increase the solubility and extraction of vanadium. The extraction of vanadium (V) was found to be limited by solubility. To overcome the solubility problem of vanadium (V), the kinetics of vanadium leaching from vanadium pentoxide at mildly basic pHs and reductive leaching in the low acidic pHs were then investigated. The kinetics of leaching was reasonably fast in both cases. Moreover, the progressive-conversion model was applied to model reductive leaching of vanadium using sodium sulfite. The rate of the reaction was reported as:rate=k*H+Ke+H+0.5SO2total0.57.