Alginate-based supermacroporous hydrogels fabricated by cryo-polymerization for uranium extraction from seawater

Uranium extraction from seawater (UES) has important strategic significance as it can provide a solution to alleviate the future shortage of uranium resources for nuclear power production. This work reports an alginate-based three-dimensional (3D) supermacroporous AO-PAM/Alg hydrogel fabricated by facile cryo-polymerization and two-step grafting modification for efficient UES. The supermacroporous and 3D interconnected pore structure of AO-PAM/Alg facilitates an increased contact flux of seawater and the diffusion rate of uranyl ions. It shows a maximum uranium adsorption capacity of 1375 mg g⁻¹ at room temperature (25 °C) and a pH of 6.0. In seawater, AO-PAM/Alg reaches adsorption equilibrium within 20 days, with a final adsorption capacity of 6.23 mg g⁻¹. AO-PAM/Alg also exhibits considerable reusability and adsorption selectivity. The current AO-PAM/Alg hydrogel holds great potential for practical UES. The current macroporous adsorbent preparation strategy can be further applied to other 3D supermacroporous adsorbent materials.