Sodium carbonate roasting and mild acid leaching of vanadium titanomagnetite concentrates: Vanadium extraction and residue sodium decrease

Abstract

Vanadium titanomagnetite is a crucial resource for vanadium and titanium. The traditional process of treating vanadium titanomagnetite concentrates has shortcomings like low vanadium recovery rate and titanium recovery inability, resulting in resource wasting and solid waste discharging. Thus, a new process of Na2CO3 roasting and mild H2SO4 leaching has been proposed. In the concentrates, titanium occurs majorly in titanomagnetite (Fe3-xTixO4, 0≤x≤1) and ilmenite (FeTiO3), vanadium in titanomagnetite and sphene (CaTiSiO5), calcium in sphene, and silicon and aluminum in several minerals. Phases are tuned during Na2CO3 roasting, where V and impurities Al and Si transform into soluble sodium compounds, leachable phase sphene doesn't change, and Ti is enriched in insoluble phases. Then, leached by mild H2SO4, the soluble compounds are almost all leached, and the leaching rates of V, Ca, Al, and Si are 91%, 76%, 84%, and 82%, respectively. The Na2O content in the leaching residue decreases to 1.0 wt%, which enables the residue for Ti extraction. This process is expected to recover V and Ti comprehensively from the vanadium titanomagnetite concentrates. The roasting kinetics are also studied based on CO2 content in the off-gas for a deeper understanding of the mechanism.