Red Mud as a Secondary Resource of Low-Grade Iron: A Global Perspective

Managing red mud (RM), a solid waste byproduct of the alumina recovery process, is a serious ecological and environmental issue. With ~150 million tons/year of RM being generated globally, nearly 4.6 billion tons of RM are presently stored in vast waste reserves. RM can be a valuable resource of metals, minor elements, and rare earth elements. The suitability of RM as a low-grade iron resource was assessed in this study. The utilization of RM as a material resource in several commercial, industrial operations was briefly reviewed. Key features of iron recovery techniques, such as magnetic separation, carbothermal reduction, smelting reduction, acid leaching, and hydrothermal techniques were presented. RMs from different parts of the globe including India, China, Greece, Italy, France, and Russia were examined for their iron recovery potential. Data on RM composition, iron recovery, techniques, and yields was presented. The composition range of RMs examined were: Fe2O3: 28.3–63.2 wt.%; Al2O3: 6.9–26.53 wt.%; SiO2: 2.3–22.0 wt.%; Na2O: 0.27–13.44 wt.%; CaO: 0.26–23.8 wt.%; Al2O3/SiO2: 0.3–4.6. Even with a high alumina content and high Al2O3/SiO2 ratios, it was possible to recover iron in all cases, showing the significant potential of RM as a secondary resource of low-grade iron.