Stepwise extraction of valuable components from red mud based on reductive roasting with sodium salts.

The feasibility of an integrated technological route for comprehensive utilization of red mud was verified in this study. Valuable components in the mud, including Fe2O3, Al2O3 and SiO2 were stepwise extracted by magnetic separation and sulfuric acid leaching from reduced red mud, and meanwhile TiO2 was enriched in the leaching residue. Sodium salts were proved to be favorable for the magnetic separation of metallic iron and the subsequent acid leaching of Al and Si, through facilitating the reduction of iron oxides and the growth of metallic iron grains, together with enhancing the activation of Al and Si components during the roasting process. After reductive roasting in the presence of 6% Na2CO3 and 6% Na2SO4, a magnetic concentrate containing 90.2% iron with iron recovery of 95.0% was achieved from the red mud by magnetic separation. Subsequently, 94.7% Fe, 98.6% Al and 95.9% Si were extracted by dilute sulfuric acid leaching from the upper-stream non-magnetic material, yielding a TiO2-rich material with 37.8% TiO2. Furthermore, value-added products of silica gel and Al(OH)3 were prepared from the leachate by ripening and neutralizing.