Interfacially engineered polydopamine-bridged magnetic core-shell polymer composite with dense imidazole coordination sites for uranium sequestration.

Magnetic core-shell polymer composites as efficient absorbents to recover uranium from wastewater are receiving more and more attention due to their unique characteristics. Yet, the poor compatibility between inorganic magnetic core and organic polymeric shell results in the low encapsulation efficiency of polymer shell, hindering the application to treat uranium-containing wastewater. Herein, an interfacial engineering strategy was employed to develop a magnetic core-shell polymer composite Fe3O4@PDA/P(TRIM-VIM) synthesized via polydopamine (PDA)-assisted interfacial modification of Fe3O4 followed by in-situ polymerization of trimethylolpropane trimethacrylate (TRIM) and 1-vinylimidazole (VIM). This rational design integrated a robust PDA interlayer to enhance core-shell compatibility with abundant imidazole coordination sites for uranium sequestration. Notably, the material displayed a maximum uranium adsorption amount (qmax) of 644.4 mg g-1 at pH 4.5, surpassing most of the adsorbents. The separation factor SU/M value for Fe3O4@PDA/P(TRIM-VIM) concerning all interfering metallic cations surpassed 7.2, and the largest value for SU/M could amount to 50.32, suggesting good selectivity for uranium. XPS and DFT analysis results demonstrated uranium removal predominantly occurred via chelation with nitrogen element of CN of imidazole, and the geometric structure that the two imidazole groups of the two distinct polymeric chains binding one UO22+ could depict the adsorption process better. Besides, the residual concentration of uranium of the treated real wastewater was dropped to levels below the standard limit value for drinking water quality (0.03 mg L-1). This work highlights an interfacial engineering strategy for designing high-performance, recyclable magnetic adsorbents for uranium removal.