Reduction roasting-magnetic separation of vanadium tailings in presence of sodium sulfate and its mechanisms

Reduction roasting with sodium sulfate fol- lowed by magnetic separation was investigated to utilize vanadium tailings with total iron grade of 54.90 wt% and TiO2 content of 17.40 wt%. The results show that after reduction roasting-magnetic separation with sodium sul- fate dosage of 2 wt% at roasting temperature of 1150℃ for roasting time of 120 min, metallic iron concentrate with total iron grade of 90.20 wt%, iron recovery rate of 97.56 % and TiO2 content of 4.85 wt% is obtained and high-titanium slag with TiO2 content of 57.31 wt% and TiO2 recovery rate of 80.27 % is also obtained. The results show that sodium sulfate has a catalytic effect on the reduction of tailings in the novel process by thermody- namics, scanning electron microscopy （SEM） and X-ray diffraction （XRD） and reacts with silica and alumina in the tailings to form sodium silicate and sodium aluminosili- cate. Migration of elements and chemical reactions destroy the crystal structures of minerals and promote the reduction of vanadium tailings, resulting in that iron grains grow to large size so that metallic iron concentrate with high total iron grade and low TiO2 content is obtained.