Removal, conversion and utilization technologies of alkali components in bayer red mud

Bayer red mud is a highly alkaline industrial solid waste generated during alumina production, and its massive discharge and stockpiling poses significant environmental risks. The strong alkalinity of red mud is a primary challenge limiting its effective utilization. This study systematically analyzes the composition and characteristics of alkaline components in red mud, emphasizing the roles of soluble free alkali and chemically bound alkali in regulating its alkalinity. A comprehensive review of current dealkalization technologies, including acid neutralization, CO2 neutralization, and salt precipitation/replacement methods is presented, focusing on their chemical mechanisms, applicability, advantages, and limitations. Specially, this study present the concept of in-situ conversion and utilization of alkali and highlight the beneficial role of alkali components in red mud recycling. The latest technologies for the conversion and utilization of alkali components, including the special roles and principles of alkali in the reaction processes of cement clinker calcination, cement hydration, geopolymers were systematically summarized. Additionally, the environmental potential of red mud in acid wastewater neutralization and flue gas desulfurization is discussed. This study identifies the technical barriers that need to be solved urgently in the current research and proposes a key direction for future study on the regulation of alkali components in red mud.