Amidoxime-functionalized SA-GQDs composite gel microspheres for efficient uranium adsorption

A composite gel microsphere with a three-dimensional porous network structure has been developed: AO/SA-GQDs. • Under the same adsorption conditions, the introduction of GQDs increased the uranium adsorption capacity of the material from 52.584 mg·g −1 to 186.996 mg·g −1 . • AO/SA-GQDs composite gel microspheres exhibited a rapid U(VI) adsorption rate, reaching adsorption equilibrium within 300 min. • The highest experimental U(VI) adsorption capacity reached 231.593 mg·g −1 at 298.15 K and pH 5. • After five cycles, AO/SA-GQDs retained 84.99% of its initial adsorption capacity, with desorption rate above 80%. • The material is easy to prepare, and its raw materials are readily available and inexpensive, suggesting its potential for practical application. Stable uranium supply is essential for the development of nuclear power, and uranium extraction from seawater is regarded as a promising strategy for the sustainable development of nuclear energy. In this study, amidoxime-functionalized sodium alginate/graphene quantum dot composite gel microspheres (AO/SA-GQDs) were prepared via an in situ composite droplet-ion cross-linking method. Sodium alginate served as the matrix, amidoxime groups were introduced as U(VI)-specific binding sites, and graphene quantum dots (GQDs) were incorporated to regulate the pore structure and hydrophilicity of the microspheres. The AO/SA-GQDs microspheres exhibited a porous network structure, with a BET specific surface area of 42.997 m 2 ∙g −1 . Batch adsorption experiments showed that the optimal adsorption pH was 5. Adsorption kinetic analysis demonstrated that the AO/SA-GQDs microspheres reached adsorption equilibrium within 300 min, indicating a rapid U(VI) adsorption rate. At 298.15 K and pH 5, the highest experimentally measured equilibrium adsorption capacity was 231.593 mg∙g −1 , whereas the Langmuir-fitted maximum monolayer adsorption capacity was 244.499 mg∙g −1 . In the presence of various coexisting ions, the microspheres still maintained a high adsorption capacity for U(VI), demonstrating good selectivity. After five adsorption-desorption cycles, the adsorption capacity remained at more than 84% of its initial value, and the desorption efficiency remained above 80%. These results indicate that AO/SA-GQDs composite gel microspheres possess favorable adsorption capacity, selectivity, and recyclability, suggesting their potential for uranium extraction from aqueous environments. Download: Download high-res image (243KB) Download: Download full-size image