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

Abstract

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: Fe₂O₃ → Fe₃O₄ → FeO → Fe, and NaOH exhibits stronger reactivity than Na₂CO₃, 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_1.75Al_1.75Si_0.25O₄ to Na_1.95Al_1.95Si_0.05O₄, and the excessive NaOH and coal additions lead to the transformation of Fe₃O₄ to NaFe_0.75Al_0.25O₂ and FeO, which significantly deteriorates the iron recovery property. The non-magnetic compounds of SiO₂ and CaTiO₃ can be separated by the magnetic separation. The optimal conditions for the magnetization reduction were obtained, and the Al₂O₃ and Na₂O recovery efficiencies of roasting product are 81.56 % and 90.97 %. The TFe, Al₂O₃ and Na₂O 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 %.