Carboxymethylcellulose-based zwitterionic cryogels for efficient U(VI) extraction from water

[Display omitted] •The hydrogel synthesized with supermacroporous structure for uranium adsorption.•The hydrogel exhibits high hydrophilicity, mechanical strength, and anti-bacteria.•The hydrogel could obtain 12.95 mg g−1 of uranium in seawater.•Zwitterions have a synergistic effect in uranium adsorption. Carboxymethylcellulose-based zwitterionic cryogels (AO-PAM/CMC) with a supermacroporous pore structure were prepared through cryo-polymerization and post-modification strategies. The hydrogel exhibited a supermacroporous structure, excellent hydrophilicity, superior mechanical properties, and resistance to biological contamination. Through a comprehensive investigation of the U(VI) adsorption process, it was observed that the AO-PAM/CMC hydrogel was predominantly characterized by chemisorption, wherein uranyl ions were adsorbed on the surface in the form of a monolayer. Under the conditions of 45 °C and pH = 5.0, the hydrogel demonstrated remarkable adsorption performance, with the maximum adsorption capacity reaching 1223.6 mg∙g−1, showcasing a high degree of selectivity for U(VI). In real seawater, the hydrogel's adsorption capacity for uranium reached 12.95 mg∙g−1 after 25 days of exposure, with the adsorption equilibrium being essentially reached in about 10 days. The adsorption mechanism of U(VI) by the hydrogel was confirmed through XPS spectroscopy and DFT calculations. The synergistic interplay between guanidino and zwitterionic moieties within the AO-PAM/CMC hydrogel enhanced U(VI) adsorption capacity and facilitated rapid uranium extraction from seawater. (UES). Therefore, the AO-PAM/CMC hydrogel presents a novel solution to address the inefficiencies of existing technologies for uranium extraction from seawater, contributing an innovative approach to the sustain-able development of nuclear energy.