Function-oriented network of bifunctional poly(amidoxime-ethyleneimine) decorated on graphene oxide for synergistically enhanced uranium extraction from seawater

Efficient uranium extraction from seawater is crucial for sustainable nuclear energy and environmental protection. Designing adsorbents with bifunctional groups that act synergistically for uranium extraction is highly desirable. Herein, leveraging the high uranyl affinity of amidoxime and the modifiable, hydrophilic nature of ethyleneimine groups, we developed a graphene oxide (GO)-based bifunctional hydrogel decorated with a 3D function-oriented network of poly(amidoxime)-poly(ethyleneimine) (PPGA@GO-H), immobilized via a simple supramolecular and covalent cross-linking approach. Detailed characterization showed excellent hydrophilicity and uniform distribution of bifunctional network, enabling PPGA@GO-H achieving high adsorption capacity of 956.1 mg g- 1 and uranium selectivity of 33.35 mg g- 1, three times higher than vanadium (10.96 mg g- 1) in simulated seawater. Meanwhile, PPGA@GO-H also maintained good performance in high levels of natural organic matter and coexisting anions (NO3- , Cl- , HCO3- , I-, and SO42- ). XPS and FTIR analysis confirmed uranyl coordination with amidoxime, amine, and carboxyl groups. Moreover, DFT calculations revealed synergistically strong electron donation from amidoxime and amines to uranium, resulting in stable complexes of the lowest Ebinding - 8.913 eV. The hydrogel retained 85 % of its adsorption capacity after five cycles and achieved 83.9-95.1 % uranyl capturing efficiency (83.9 - 95.1 %) in real seawater. These results demonstrate that PPGA@GO-H provides new insights for designing novel materials with addressing the limitations of conventional PAO-based adsorbents in uranium extraction applications.