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

A PEG-enhanced phosphate modification strategy was proposed for chitosan-SiO 2 aerogel. • PEG improves structural stability while phosphate introduces U(VI)-binding sites. • CSA/PEG-PO 4 exhibits a high U(VI) capacity of 496.98 mg g −1 at pH = 4. • Amino, hydroxyl and phosphate groups synergistically promote U(VI) adsorption. • The aerogel shows potential for efficient uranium removal from acidic wastewater. 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-PO 4 ) 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 Mg 2+ and Ca 2+ . 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-PO 4 is a promising adsorbent for the efficient removal of U(VI) from aqueous solutions.