High-performance membrane for rapid and selective extraction of uranium from simulated seawater: A novel polyacrylonitrile-poly(amidoxime) hydrogel membrane material

The development of efficient, selective, and readily regenerable adsorbents for uranium extraction from seawater has been a research focus. In this study, the polyacrylonitrile-poly(amidoxime) (PAN-PAO) composite membrane with remarkable uranium adsorption capacity was rapidly prepared by a nonsolvent induce phase separation method. The membrane was then treated with alkaline to enhance membrane swelling, exposing PAO to promote binding to uranium. The fitting results of the adsorption kinetics and thermodynamic models indicate that the pseudo-second-order model and Langmuir adsorption isotherm can better explain the adsorption process, and the maximum adsorption capacity of uranium reached 835.8 mg/g based on the Langmuir model with pH 5 and 298 K. The PAN-PAO hydrogel membrane demonstrated a high adsorption rate of uranium in simulated seawater, reaching up to 90 % under the interference of multiple co-existing ions. Additionally, the selectivity coefficient of U to V reached 3.5. After six adsorption and desorption cycles using 0.5 mol/L NaHCO3 and 0.25 mol/L Na2CO3 + 0.025 mol/L H2O2 as eluents, the adsorption capacity of the membrane remained above 85 % of the initial value, and the desorption rate were consistently above 90 %. The membrane shows great promise as a material for efficient, selective, and sustainable extraction of uranium from seawater.