Recovery of titanium and vanadium from titanium–vanadium slag obtained by direct reduction of titanomagnetite concentrates

A process of NaOH molten salt roasting–water leaching to treat titanium–vanadium slag obtained by direct reduction of titanomagnetite concentrates was investigated. X-ray diffraction (XRD), scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS), and thermogravimetry–differential scanning calorimetry (TG–DSC) techniques were used to characterize the samples. The results show that anosovite (Mg_xTi_3−xO₅) and clinopyroxene [Ca(Ti,MgAl)(SiAl)₂O₆] are the major phases of titanium–vanadium slag. In the NaOH molten salt roasting process, titanium is converted to intermediate product Na₂TiO₃ and vanadium is converted to water-soluble vanadate. The response surface methodology (RSM) was used to optimize the roasting process conditions. NaOH to slag mass ratio (N/S) and roasting temperature are the main influential factors. Under the optimal roasting conditions, i.e., roasting temperature of 550 °C, N/S of 1.20, and roasting time of 80 min, the conversions of titanium and vanadium are 96.5 % and 93.0 %, respectively. In the water leaching process, Na₂TiO₃ is converted to amorphous structure of H₂TiO₃ since Na⁺ is exchanged with H⁺. Up to 93.0 % vanadium is leached out under the optimal leaching conditions. Titanium and vanadium in the titanium–vanadium slag can be separated and then recovered.