Polyacrylamide-Intercalated MXene Nanosheets Loaded with ZIF-8 for Uranium Adsorption

The extraction of uranium from seawater is crucial for the advancement of sustainable energy development, driving urgent demands for high-performance adsorbents. Herein, a composite adsorbent was engineered based on MXene nanosheets. To address the self-stacking issue of the nanosheets, polyacrylamide (PAM) was intercalated as a molecular spacer, which was followed by the in situ growth of zeolitic imidazolate framework-8 (ZIF-8) on the modified MXene nanosheet surface. The material exhibited a hierarchical pore structure and high specific surface area (604 m2/g), facilitating active site exposure. Maximum uranium adsorption capacity reached 909 mg/g at pH 4.0 and 298 K, with high selectivity. Adsorption kinetics conformed to a pseudo-second-order model, isotherms aligned with the Temkin model, and thermodynamics revealed a spontaneous, endothermic process. FT-IR and XPS spectroscopy confirmed the UO22+ coordination with MXene (Ti–O, –COOH), PAM (–NH2), and ZIF-8 (pyrrole-N, Zn–O). The material maintained stable performance in complex aqueous environments, exhibiting uranium adsorption capacities of 33, 34, and 37 mg/g in spiked salt lake water, seawater, and Yellow River water systems, respectively. This work has provided valuable insights for designing MXene-based adsorbents for uranium extraction from natural water.