Recovery of valuable metals from red mud: A comprehensive review

As a bulk solid waste with high alkalinity, red mud (RM) not only occupies a large amount of land and requires high maintenance costs, but also unavoidably generates serious hazards to the surrounding ecological environment. The comprehensive treatment of RM has become an enormous challenge for the green, low-carbon and high-quality development of the global alumina industry. To minimize the RM destruction to the ecology and the waste of secondary resources, the sustainable utilization of RM was widely investigated in the past decades, especially for the recovery of valuable metals. This paper systematically summarized the research status of recycling valuable metals (Al, Fe, Na, Ti, Sc, Ga, V and RE) from RM in recent years. The recycling technology mainly includes physical beneficiation, hydrometallurgy, pyrometallurgy and electrodialysis. The technical principles and characteristics as well as the current problems of various recovery processes from RM were comprehensively introduced, and the future development directions of sustainable utilization were also prospected. The advantages and disadvantages based on the different aspects of recovery efficiency, energy consumption and environmental impact were also discussed. The proposal of new technologies for the harmless, high-value and full utilization of RM is beneficial to the future research on the comprehensive utilization of bulk industrial solid wastes.