From hazardous solid waste to resource utilization: a technical review of efficient iron resource recovery from red mud

Abstract Iron is a foundational bulk commodity in China. However, the supply of iron ore falls far short of meeting the demands of the steel industry, leading to long-term dependence on imports. Red mud, a by-product of the alumina industry, with its high-grade iron content and polluting nature, is emerging as a novel iron resource possessing dual attributes of resource potential and environmental pollution, urgently requiring development. This paper primarily introduces the physicochemical properties of red mud. It then focuses on reviewing modern iron recovery methods from red mud, including physical separation, pyrometallurgical smelting reduction, leaching, magnetization roasting, and fluidization magnetization roasting, detailing their reaction mechanisms and process characteristics. Existing technologies generally face technical bottlenecks such as high energy consumption, low iron phase conversion efficiency, suppression of separation efficiency by alkaline components, and secondary pollutant emissions. The variability in red mud composition and the complexity of mineralogical occurrence also present multiple challenges. Current development trends focus on creating low-temperature, high-efficiency, and environmentally friendly combined process systems. By coupling the advantages of microwave selective heating with enhanced mass transfer in fluidization, microwave fluidization magnetization roasting technology enables the targeted conversion of hematite to magnetite under low-temperature conditions, thereby achieving high-efficiency iron recovery.