A chitosan-based interconnected porous ionic gel constructed via cryo-polymerization for uranium extraction from seawater

Uranium extraction from seawater faces several challenges, such as extremely low uranium concentration, hydrogel adsorbents’ structural collapse under seawater pressure, and reduced adsorption efficiency in weakly alkaline conditions. To address these issues, a dual-crosslinked hydrogel matrix (CS/PAA) was developed via a one-step cryo-polymerization strategy. By integrating chemically crosslinked polyacrylic acid (PAA) and ionically crosslinked chitosan (CS), the hydrogel achieved a robust 3D interconnected porous structure with a compressive strength of 134.71 kPa. The introduction of amidoxime (AO) groups into CS/PAA further enhanced uranium adsorption, resulting in the CS/P(AA-co-AO) ionic gel. Notably, this hydrogel retained its porous architecture after ambient drying, offering a low-energy alternative to freeze-drying. The presence of chitosan not only imparts antibacterial properties but also stabilizes the gel structure under seawater conditions. The interconnected macroporous network facilitates rapid mass transfer, enabling an adsorption capacity of 11.92 mg·g⁻¹ after 30 days in natural seawater. This innovative ionic gel, combining enhanced structural stability, environmental adaptability, and low-energy preparation, provides a promising strategy for efficient uranium recovery, addressing key limitations of conventional adsorbents.