Recent Advances in Novel Adsorbents Prepared by the Sol–Gel Method for the Removal of Uranium and Strontium from Radioactive Wastewater: A Review

Uranium- and strontium-containing wastewater from nuclear industries poses a threat to the environment and human health. The sol–gel method, with its tunable composition and synthetic flexibility, is widely used to fabricate novel and high-performance adsorbents. This review covers recent progress in the sol–gel fabrication of UO22+ and Sr2+ adsorbents, including both inorganic and organic–inorganic hybrid materials. Reported adsorption capacities typically range from about 40 to 670 mg/g for UO22+ and from about 40 to 370 mg/g for Sr2+, with a few systems achieving even higher values under optimized conditions. Titanates and titanosilicates exhibit outstanding selectivity toward Sr2+, whereas phosphate-based materials and amidoxime-functionalized hybrids show strong affinity for UO22+. However, practical application is still hampered by high precursor costs, poor shapeability, limited long-term stability, harsh regeneration conditions, and interference from coexisting ions. Future efforts should focus on low-cost materials and shaping processes to promote the engineering applications of tailored materials via the sol–gel method.