Efficient removal of uranium(vi) from simulated seawater using amidoximated polyacrylonitrile/FeOOH composites

The ability to recover uranium, an important nuclear fuel, from seawater provides the potential for long-term sustainable fuel supply for nuclear energy. In this work, novel amidoximated polyacrylonitrile/FeOOH (FeOOH-APAN) composites were synthesized and characterized by CHN analysis, Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), N₂ adsorption-desorption, and X-ray photoelectron spectroscopy (XPS). In batch adsorption experiments, a variety of parameters were investigated in detail. The FeOOH-APAN composites exhibit high adsorption capacities (q_L = 980.39 mg g^-1, T = 298 K), superior to many other materials. In addition, they possess large K_d values (>10⁴ mL g^-1 at 25-400 mg L^-1 U concentration), high removal rates (∼95% at 25-300 mg L^-1, and ∼90% for ppb level simulated seawater), excellent selectivity and rapid capturing rates for uranium. XPS analysis shows that the removal of uranium is mainly related to amidoxime groups, involving the interaction with oxime oxygen and oxime nitrogen. In this paper, a more dominant binding mode is proposed, namely η² coordination.