Fabrication of a chitosan/carboxymethyl cellulose composite foam with phytic acid-modified hydrotalcite for highly efficient U(VI) removal from aqueous solution

The nuclear industry's production generates significant uranium-containing wastewater. Owing to radioactivity, this wastewater seriously threatens environmental safety and human health, becoming a major bottleneck for nuclear energy's sustainable development. Adsorption-based uranium extraction from radioactive wastewater represents a promising strategy, as it facilitates the recovery of a valuable resource while significantly mitigating environmental pollution. Chitosan contains active functional groups like amino groups and hydroxyl groups, this study employed chitosan cross-linking and composite technology, supplemented by freeze-drying methods. Based on the synergy of multi-functional groups, a composite foam adsorbent (HPC) was constructed, which consists of phytic acid-modified layered hydrotalcite rich in phosphate groups and chitosan/carboxymethyl cellulose. This adsorbent was employed for the removal of U(VI) from aqueous solutions, and its adsorption performance was systematically evaluated under various conditions. The results demonstrated that under optimal conditions, the maximum adsorption capacity for U(VI) reached 272.28 mg/g. The adsorption process was well described by the pseudo-second-order kinetic model and the Langmuir isotherm, indicating monolayer chemisorption. Thermodynamic studies revealed that the adsorption is spontaneous and exothermic in nature. The HPC adsorbent possesses a high specific surface area and is rich in diverse functional groups, including carboxyl, hydroxyl, amino, and phosphate groups. The synergistic effect among these functional groups enhances U(VI) adsorption through mechanisms such as chemical complexation, ion exchange, and isomorphic substitution. These findings suggest that HPC is a promising high-performance adsorbent for the treatment of uranium-containing radioactive wastewater.