Extraction of Vanadium from Vanadium–Titanium Magnetite: Enhanced by Sodium–Calcium Synergistic Roasting–Water Leaching Process

The sodium roasting–water leaching process for vanadium–titanium magnetite (VTM) concentrate faces challenges such as low vanadium recovery, excessive addition of sodium salt, and high alkali content in the tailings. Therefore, reducing the presence of toxic elements like vanadium and alkali metal sodium in the extraction tailings is crucial for the comprehensive utilization of VTM concentrate. This study proposes an innovative technique involving sodium–calcium synergistic roasting that holds potential to enhance vanadium recovery and mitigate the adverse effects of sodium salt. The leaching efficiency of vanadium from VTM concentrate was initially examined using two conventional processes: sodium roasting–water leaching and calcification roasting–acid leaching, which utilize Na₂CO₃ and CaCO₃ as additives, respectively. Then, the effect of a sodium–calcium synergistic roasting–water leaching process, which involved roasting with a composite additive comprising Na₂CO₃ and CaCO₃, was investigated. The results demonstrate that the sodium roasting–water leaching process achieves a maximum vanadium leaching efficiency of 71.9 wt pct, whereas the calcification roasting–acid leaching process yields a vanadium leaching efficiency below 50 wt pct. However, by employing a sodium–calcium synergistic roasting technique, the leaching efficiency of vanadium can be enhanced to 75.19 wt pct. Moreover, this technique effectively reduces the Na₂CO₃ addition amount from 6 to 4 wt pct, while substituting it with an easily accessible and cost-effective CaCO₃ at a dosage of 3 wt pct. This substitution also results in a decrease in alkaline content of Na in the extraction tailings from 2.36 to 1.79 pct, thereby facilitating subsequent comprehensive utilization process.