Polyethylene glycol-enhanced phosphate-modified chitosan/SiO₂ hybrid aerogel for efficient uranium(VI) adsorption...

Uranium contamination has become an important environmental issue because of its toxicity and radiological hazards. In this work, a polyethylene glycol (PEG)-enhanced phosphate-functionalized chitosan-silica hybrid aerogel (CSA/PEG-PO₄) was successfully prepared by the sol-gel method and freeze-drying. The structure and surface properties of the aerogel were characterized by XRD, FT-IR, SEM, BET and XPS. Compared with the chitosan/silica aerogel (CSA), PEG modification improved the adsorption performance, while phosphate modification further enhanced the adsorption capacity toward U(VI). The maximum adsorption capacity was 496.98 mg g^-1 (pH 4.0, m/V = 1 g L^-1, 150 min, 298 K, 150 rpm), while the removal efficiency reached 97.9%. The adsorbent also showed good selectivity toward U(VI), maintaining removal efficiencies above 87% in the presence of common coexisting ions such as Mg²⁺ and Ca²⁺. The pseudo-second-order kinetic model provided a better fit to the adsorption data. Intraparticle diffusion analysis showed that intraparticle diffusion was not the only rate-controlling step. FT-IR and XPS analyses indicated that hydroxyl, amino and phosphate groups were the main active sites for U(VI) adsorption. XRD results confirmed that the aerogel maintained a stable amorphous framework after adsorption, indicating good structural stability during the adsorption process. Overall, CSA/PEG-PO₄ is a promising adsorbent for the efficient removal of U(VI) from aqueous solutions.