Poly(amidoxime)/polyzwitterionic semi-interpenetrating network hydrogel with robust salt-shrinkage resistance for enhanced uranium extraction from seawater

Effective uranium extraction from seawater can contribute greatly for meeting the needs of low carbon energy. Extensive studies have been conducted on polyamidoxime-based (PAO-based) adsorbents for their exceptional uranium adsorption capabilities. However, the salt-shrinkage effect severely hinders the extraction of uranium from seawater using traditional PAO-based adsorbents. This study synthesizes a novel semi-interpenetrating polymer network hydrogel, designated as PAO/PMPC-SH, using a free-radical polymerization approach utilizing PAO and zwitterionic poly (2-methacryloyloxyethyl phosphorylcholine) (PMPC). The incorporation of the PMPC component endows the adsorbent with exceptional resistance to salt shrinkage owing to the antipolyelectrolyte effect. This characteristic facilitates the diffusion of uranyl ions within PAO/PMPC-SH, even in a high-salt environment with a salt concentration as high as 25 wt%, thereby exposing the uranium binding sites in the adsorbent. Moreover, PAO/PMPC-SH exhibits exceptional antibacterial activity. After 28 days of test in natural seawater, PAO/PMPC-SH demonstrates a high uranium extraction capacity of 6.26 mg g-1, representing only a 9.14 % decrease compared with the capacity of adsorbing in marine microorganism-removed natural seawater. Overall, the notable performance of PAO/PMPC-SH in uranium extraction highlights its potential as a highly effective adsorbent for uranium extraction from seawater.