Abstract: Red mud is a highly alkaline waste produced in the process of refining alumina from bauxite. Due to the rapid development of the aluminum industry, the annual discharge of red mud in the world has seriously exceeded the environmental load, resulting in huge disposal pressure and pollution risks. Therefore, the efficient utilization of red mud as a resource is imminent. The preparation of layered double hydroxide (LDH) from red mud is a circulating route, and has the potential for large-scale industrialization. This paper reviews the research progress of red mud based LDH synthesis technology and application. It is found that the main synthesis processes include co-precipitation, calcination-hydration and mechanochemical methods. The synthesized red mud-based LDH type is affected by bauxite composition and smelting technology. Significant impact. Red mud based LDH is typically used as an absorbent to remove inorganic pollutants and capture CO2, and it is also a new environmentally friendly halogen-free flame retardant additive. Red mud based LDH is also an excellent photocatalyst, and the introduction of impurities(Fe2O3) in red mud leads to the local construction of heterostructures, which is beneficial to the separation and transfer of photosensitive electrons and holes. Finally, this paper puts forward the following prospects: (1) In the context of carbon neutral targets, the preparation of red mud based LDH meets the sustainable development goals such as “circular economy” and has practical potential for large-scale

application, and the synthesis and application research should be vigorously promoted; (2) It should focus on how to further optimize the synthesis process, improve yield, enhance sustainability (such as introducing other wastes as divalent metal sources), improve synthesis specificity, and reduce the environmental risk of red mud-based LDH in the application process; (3) Understand the relationship between LDH properties and its performance, and exploit the advantages of the heterostructure of red mud based LDH achieve a more efficient a pplication.

Key words: red mud, layered double hydroxide (LDH), absorption, catalysis, flame retardant