Efficient recovery of iron and alumina from red mud by alkali-enhanced magnetization reduction

In order to achieve the efficient abatement of red mud and recover its valuable metals, the thermodynamics, mineral transformation and reaction mechanism of alkali-enhanced magnetization reduction were systematically investigated. The thermodynamic results indicate that the reaction sequence of iron oxides with the increasing CO partial pressure follows: Fe 2 O 3 → Fe 3 O 4 → FeO → Fe, and NaOH exhibits stronger reactivity than Na 2 CO 3 , which can react more easily with the non-ferrous oxides of red mud. The increase of roasting temperature and NaOH dosage promotes the conversation of Na 1.75 Al 1.75 Si 0.25 O 4 to Na 1.95 Al 1.95 Si 0.05 O 4 , and the excessive NaOH and coal additions lead to the transformation of Fe 3 O 4 to NaFe 0.75 Al 0.25 O 2 and FeO, which significantly deteriorates the iron recovery property. The non-magnetic compounds of SiO 2 and CaTiO 3 can be separated by the magnetic separation. The optimal conditions for the magnetization reduction were obtained, and the Al 2 O 3 and Na 2 O recovery efficiencies of roasting product are 81.56 % and 90.97 %. The TFe, Al 2 O 3 and Na 2 O contents of iron concentrate are 55.21 %, 3.87 % and 0.82 %, while the corresponding yield and iron recovery efficiency are 87.97 % and 90.37 %.