Chromium and iron recovery from hazardous extracted vanadium tailings via direct reduction magnetic separation

Abstract

The large accumulation of extracted vanadium tailings not only causes a waste of resources but also leads to environmental pollution. In this work, a technique was proposed that involves direct reduction followed by magnetic separation for recovering Fe and Cr while removing Na from the extracted vanadium tailings. Thermodynamic analysis and process parameters such as the use of additives and the reduction temperature were experimentally determined. Thermodynamic results showed that a reduction temperature higher than 1250 °C is required for the simultaneous removal of sodium, iron, and chromium. The experimental results indicated that when the Ca (OH)2 addition was added at a rate of 30 %, and the reduction temperature was maintained at 1350 °C for 2 h, Fe-Cr alloys were formed by the reduction of iron and chromium and could be separated by magnetic separation. The addition of Ca (OH)2 greatly facilitates the reduction of the Fe-containing phase in the extracted vanadium tailings, resulting in the formation of Fe-Cr alloy with reduced Cr. Sodium metal was volatilized, with removal rates of 65.9 %, 93.3 % and 93.32 % for Cr, Fe and Na, respectively. The recovery efficiencies for Fe and Cr were 85.9 % and 65.4 % respectively. The magnetic concentrate contained 83.84 % total Fe and 7.25 % Cr, and its main phase was Fe-Cr alloy. In contrast, the magnetic tailing consisted mainly of CaTiO3. The simultaneous method has a significant impact on removing valuable metals and reducing the environmental risk of the extracted vanadium tailings.