Hollow Zn/Co zeolitic imidazolate framework-implanted composite hydrogel for highly efficient uranium extraction from seawater

Efficient capture of uranium(VI) (U(VI)) from seawater is of great significance to the sustainable development of nuclear energy and environmental protection, which is also a serious challenge at present. In this study, hollow Zn/Co zeolitic imidazolate framework (H-ZIF) was decorated on polyacrylamide/sodium alginate (PAM/SA) hydrogel by chelating and covalently crosslinking, and a new type of PAM/SA/H-ZIF hydrogel was synthesized. The combination of PAM/SA and H-ZIF gives PAM/SA/H-ZIF hydrogel excellent mechanical properties, good stability, and abundant surface functional groups, which is beneficial to improving the adsorption properties. The extraction amount of U(VI) by PAM/SA/H-ZIF is 171.14 mg·g⁻¹ at C₀ = 99.52 mg·L⁻¹ and pH = 5.0. The adsorption equilibrium is reached in 120 min and the adsorption process fits well with Langmuir isotherm model and pseudo-second-order rate equation. The PAM/SA/H-ZIF also showed good recyclability and stability after 10 cycles of adsorption–desorption. More importantly, the rate of uranium adsorption is 0.196 mg·g⁻¹·day⁻¹ after 30 days, which implies that the PAM/SA/H-ZIF could serve as a potential adsorbent for the development of uranium capture from seawater.