A Review of Metal Oxide-Based Materials for U(VI) Sequestration from Aqueous Media

Uranium contamination in aquatic environments has raised increasing concerns because of its chemical toxicity and radioactivity, creating a persistent demand for efficient uranium sequestration and recovery technologies. Metal oxides have attracted considerable attention as materials for U(VI) sequestration owing to their chemical stability, tunable structures, and abundant reactive surface sites. This review systematically summarizes the fundamental chemistry and recent development of metal oxide-based materials for U(VI) sequestration from aqueous environments. The aqueous speciation of U(VI), surface chemistry of metal oxides, and major interfacial interactions governing uranium retention are first discussed. Representative materials, including iron oxides (FeOx), titanium oxides (TiO2), aluminum oxides (Al2O3), manganese oxides (MnOx), zirconium oxide (ZrO2), cerium oxide (CeO2), magnesium oxide (MgO), zinc oxide (ZnO), and mixed-metal oxide systems, are then reviewed with emphasis on their structural characteristics, uranium retention performance, modification strategies, and immobilization mechanisms. Current evidence demonstrates that U(VI) sequestration is strongly governed by the nature and accessibility of surface hydroxyl and metal-oxygen sites, which can be further regulated through structural modification, surface functionalization, defect engineering, and the construction of mixed-metal oxide systems. This review provides a systematic understanding of the relationships among oxide composition, surface structure, interfacial chemistry, and U(VI) sequestration behavior, offering guidance for the rational design of advanced metal oxide-based uranium sequestration materials.