One-Pot Microemulsion Synthesis of Hierarchical SiO ₂ –TiO ₂ –Carbon for Selective Adsorption of Radionuclides

Effective management of radioactive wastewater relies on advanced adsorbents capable of maintaining high selectivity in complex environments. A hierarchical SiO2–TiO2@C composite was synthesized through a microemulsion method by using Pluronic P-123. Comprehensive characterization, including SEM, HR-TEM, EDX, XRD, BET, and XPS, confirmed its ordered hexagonal mesostructure. The SiO2–TiO2@C composite exhibited a high surface area of 378 m2/g and uniform pores measuring 11.9 nm. It demonstrated high adsorption capacities of 50.2 mg/g for Cs(I) and 68 mg/g for Sr(II). The material showed good selectivity, achieving approximately 89.4 and 93.7% removal for Cs(I) and Sr(II), respectively, and retained 77.5 and 82.0% efficiency in real seawater. It also displayed excellent regenerability, maintaining about 75.5% of its capacity for Cs(I) and 84.1% for Sr(II) after nine cycles, which underscores its strong potential for practical wastewater treatment applications. The adsorption proceeds via ion exchange and surface complexation with hydroxyl groups. The carbon phase enhances the surface acidity and site availability. For Sr(II), complexation with hydrolyzed SrOH+ species is particularly effective, while Cs(I) uptake occurs primarily through ion exchange at acidic sites and selective pore entrapment.