An Ion-Crosslinked Supramolecular Hydrogel for Ultrahigh and Fast Uranium Recovery from Seawater

Large-scale uranium extraction from seawater is a crucial but challenging part of nuclear power generation. In this study, a new ion-crosslinked supramolecular Zn²⁺ -poly(amidoxime) (PAO) hydrogel that can super-efficiently adsorb uranium from seawater is explored. By simply mixing two solutions of zinc chloride and PAO, a supramolecular Zn²⁺ -PAO hydrogel is achieved via the interaction between zinc cations and amidoxime anions. In contrast with existing amidoxime-functionalized hydrogel-based adsorbents having low PAO contents and fiber-based adsorbents with weak hydrophilicity, the PAOs can be directly crosslinked using a small quantity of superhydrophilic zinc ion. Thus, a supramolecular hydrogel is formed, having both a high content of well-dispersed PAOs and good hydrophilicity. Relative to reported adsorbents, this low-cost hydrogel membrane exhibits outstanding uranium adsorption performance, reaching 1188 mg g^-1 of M_U /M_{dry gel} in 32 ppm uranium-spiked water. More importantly, after immersion in natural seawater for only 4 weeks, the uranium extraction capacity of the Zn²⁺ -PAO hydrogel membrane reaches 9.23 mg g^-1 of M_U /M_{dry gel} . This work can provide a general strategy for designing a new type of supramolecular hydrogel, crosslinked by various bivalent/multivalent cation-crosslinkers and even many other superhydrophilic supramolecular crosslinkers, for the high-efficient and massive extraction of uranium from seawater.