ZIF-67-Embedded Polyacrylamide/Sodium Alginate/Polyacrylic Acid Hydrogel for Efficient and Selective Uranium Extraction

The escalating global demand for nuclear energy has intensified the need for developing highly efficient and selective adsorbents for extraction of uranium from seawater. In this study, ZIF-67 is embedded into a polyacrylamide/sodium alginate/poly(acrylic acid) (PAM/SA/PAA) hydrogel through chelation and covalent cross-linking to prepare a novel PAM/SA/PAA@ZIF-67 (PSP@ZIF-67) adsorbent. PSP@ZIF-67 exhibits excellent uranium(VI) (U(VI)) adsorption performance. It reaches adsorption equilibrium within 20 h and achieves a remarkable adsorption capacity of 278.0 mg·g^-1 at a low original uranium concentration of 8 mg·L^-1. The adsorption process is well-fitted with a pseudo-second-order rate equation and Langmuir model. Furthermore, PSP@ZIF-67 displays selective adsorption of UO₂²⁺ in a complex solution containing 11 competing metal ions. PSP@ZIF-67 also demonstrates good recovery and stability after eight adsorption-desorption cycles. X-ray photoelectron spectroscopy (XPS) analysis reveals that the synergistic effects of amine groups, carboxylate ligands, and Co-O^- ligands of ZIF-67 are the primary adsorption mechanism of U(VI) adsorption. This work aims to design a hydrogel adsorbent with a porous structure and multifunctional groups, providing an important strategy for developing high-performance materials for seawater uranium extraction.