Extraction of Fe and Al from red mud using carbothermic reduction followed by water leaching

Abstract

Red mud, a solid byproduct from bauxite ore processing for Al2O3 production, encompasses valuable industrial metals, including Fe and Al. The objective of the present study was to investigate the feasibility of an integrated route for the efficient use of red mud for the multistep extraction of Fe and Al. Carbothermic roasting was performed in the presence of Na2CO3 to reduce iron oxide to metallic iron. Optimal roasting conditions (reductant dosage: 1 g, temperature: 900 °C, time: 120 min, and charge ratio 10:5:1) yielded a 95.6 % recovery of the magnetic fraction. Applying a magnetic gradient of 0.1 T resulted in a 92.5 % recovery of metallic iron. Subsequent water leaching, performed under optimal conditions (time: 120 min, temperature: 70 °C, pulp density: 10 %), achieved a 98.5 % leaching efficiency of Al from a nonmagnetic fraction, with and without sodium carbonate, demonstrating 26 % efficiency. Incorporating sodium salt during carbothermic roasting facilitated the reduction of iron oxide to metallic iron and activated alumina for leaching. Finally, a value-added Al product, AlPO4, was precipitated from the leachate. This approach primarily attempts to contribute to a more circular economy, reducing waste and minimizing the environmental impact.