The prerequisite for efficient utilization of red mud: a review of alkali component removal technologies

Abstract The high alkalinity and fine particle size of red mud, coupled with its complex symbiosis, can result in land salinization, as well as water and air pollution and the risk of dam failure. When stockpiled in the open air, it poses a potential threat to human health and safety. To mitigate the adverse effects of red mud, efficacious dealkalization technologies must be developed and implemented to reduce its alkalinity and improve its utilization as a resource. This article reviews traditional and emerging methods for alkali removal, including water washing, lime treatment, acid treatment, salt substitution, and industrial waste liquid neutralization; meanwhile, new methods such as microbial method, membrane sodium removal technology, calcium slag method, calcification carbonation method, and microwave treatment method are introduced. The paper summarizes and compares the advantages and disadvantages of these technologies, highlighting that the future challenge lies in achieving the industrial application of red mud alkali removal technology that balances economy, environmental protection, and efficiency. It also indicates that future development should focus on efficiently recovering strategic metals (such as iron, aluminum, titanium, scandium) from red mud while removing the alkali, ultimately realizing the utilization and reduction of red mud.