Bauxite Residue (Red Mud) from the Bayer Process: A Critical Review of Management, Safe Storage, Valorization, Critical-Metal Recovery, and Industrial Integration

Abstract

Bauxite residue (BR), commonly termed red mud, is the strongly alkaline, fine-grained solid generated during Bayer alumina refining. This critical review synthesizes a primary contemporary corpus of 145 publications from January 2020 to 23 September 2026, supplemented by a small set of pre-2020 foundational sources used only for historical and mechanistic context, and evaluates BR as an integrated management-and-resource system rather than an isolated waste stream. The analysis connects residue mineralogy, soluble and structural alkalinity, rheology, dewatering, geotechnical behavior, neutralization, revegetation, high-volume material use, functional applications, and recovery of Fe, Al, Ti, Sc, rare-earth elements, V, and Ga. No single route simultaneously maximizes residue uptake, metal selectivity, water recovery, environmental performance, and economic value. Mechanical dewatering and engineered dry placement reduce water inventory and can improve caustic recovery, but they do not eliminate chemical liability. Neutralization and dealkalization can enable rehabilitation and downstream utilization; however, reagent demand, salt formation, secondary-residue behavior, and long-term leaching must be treated as system variables. Construction materials represent the largest technically plausible mass-scale class of applications, although realistic regional absorption is constrained by logistics, standards, and market demand; critical-metal recovery offers greater value density but generally requires more intensive separation and purification. Pilot-scale scandium recovery demonstrates that selective products can be produced, while life-cycle studies show that drying and valorization may shift, rather than eliminate, environmental burdens. The review therefore proposes an author-developed cascade decision framework in which water and alkali recovery, conditioning, selective recovery, bulk utilization, and residual-risk management are sequenced according to site-specific feed, infrastructure, market, and regulatory conditions rather than treated as an invariant flowsheet. Priority research needs include standardized feed characterization, element-specific mass closure, comparable service-condition leaching protocols, integrated mass-water-energy balances, sustained pilot campaigns, product and regulatory qualification, and coupled life-cycle assessment (LCA), techno-economic analysis (TEA), and technology-readiness-level (TRL) assessment.