Preparation of metallic iron powder from red mud by sodium salt roasting and magnetic separation

Red mud has become one kind of the most hazardous solid waste. In order to recover iron from red mud, the technology of sodium salt roasting and magnetic separation was developed. During the reduction roasting, additives (Na2SO4 and CaO) reacted with SiO2 and Al2O3 of red mud, forming NaO.Al(2)O(3.)2SiO2, 2CaO. Al2O3. SiO2, 12CaO.7Al2O3, CaO. Al2O3 and 2CaO.SiO2, which ameliorates the separation between iron and alumina during magnetic separation. Meanwhile, sodium sulphate also improved the growth of iron grains, increasing the iron grade and iron recovery. The metallic iron powder obtained contained 90.28 wt-% TFe ( representing a metallisation degree of 94.87 wt-%) at 92.14 wt-% iron recovery under the optimum conditions, which can be briquetted as a burden material for steel making by electric arc furnace to replace scrap.