Anionically modified chitosan-coated magnetic silica particles with enhanced adsorption for uranium removal

In this study, two new, highly selective, acid-resistant and reusable functionalized magnetic chitosan-based composites (FOS@C-DTPA and FOS@C-PBTCA) were successfully prepared. The adsorption performance of the composites was systematically evaluated through controlled variations in solution pH, exposure time, and starting uranium content, while the underlying mechanisms for uranium uptake were analyzed using kinetic models and thermodynamic equilibrium studies. In the multi-ion competition experiments, a high degree of selectivity for U(VI) was demonstrated; good cyclic regeneration performance was shown in both cycling experiments. XPS analysis combined with complementary characterization techniques demonstrated that uranium adsorption was predominantly caused by surfaces complexation between U(VI) ions and the composite material’s abundant functional groups rich in carbon, nitrogen, and oxygen on the composite material. At pH 5, FOS@C-PBTCA demonstrated an adsorption capacity of 303.53 mg·g⁻¹, while FOS@C-DTPA achieved 487.39 mg·g⁻¹ at pH 6. The proposed approach aims to achieve efficient and selective uranium extraction by leveraging an anion-assisted synergistic mechanism, enabled through the rational design of acid-resistant and recyclable magnetic composite adsorbents.