Technologies for recovery of iron from red mud: Processes, challenges and opportunities

Red mud, a byproduct of alumina production, presents significant challenges due to its large-scale production and inefficient utilization, leading to substantial environmental and health hazards. Traditional disposal methods, such as land-based stockpiling, exacerbate environmental degradation, including soil and groundwater contamination, air pollution, and associated health risks. However, red mud, rich in valuable metals, particularly iron, offers a secondary resource for value-added utilization. This review evaluates various iron extraction methods, including physical, chemical, and pyrometallurgical techniques. Physical methods like magnetic separation and flotation, alongside chemical and hydrometallurgical methods like acid leaching, often encounter obstacles such as low iron recovery rates and acidic wastewater generation. Pyrometallurgical methods, despite their effectiveness, are hindered by high energy consumption and environmental concerns. Conversely, biomass pyrolytic reduction followed by magnetic separation within pyrometallurgical methods has emerged as a promising alternative. However, significant gaps remain in understanding the transformation mechanisms of iron minerals and impurities during biomass pyrolytic reduction, the kinetics of reduction specific to red mud, optimizing biomass quantities, and the nature of produced pyrolytic gases. Addressing these gaps is essential for realizing the full potential of biomass pyrolytic reduction as a sustainable solution for iron extraction from red mud, mitigating environmental impact and fostering sustainability.