Amidoxime engineering enhanced sorption performance of chitosan towards uranium from aqueous solution and simulated seawater

The highly efficient capture of uranium from seawater is a promising strategy for the future sustainable development of nuclear power. The key issue of capturing uranium from seawater is to develop novel sorbents with high selectivity and excellent sorption performance. Herein, a simple two-step hydrothermal method was used to graft acrylonitrile monomer onto chitosan matrix via free radical polymerization, and amidoxime functionalized chitosan (AOCS) was obtained by amidoximation conversion reaction. The sorption performance and selectivity of AOCS towards U(VI) in the aqueous solution and simulated seawater were investigated. AOCS shows excellent selectivity and sorption performance towards U(VI), with a maximum capture capacity of 179.36 mg/g at 303 K and pH 5.0. At the same time, AOCS exhibited rapid capture kinetics at the optimal pH condition, reaching sorption equilibrium within about 40 min. Sorption mechanisms were further elucidated by X-ray photoelectron spectroscopy, as well as a scanning and the transmission electron microscope images. It is inferred that the faster sorption rate and high sorption efficiency of AOCS towards uranium is due to the strong chelation of amidoxime groups to U(VI). The excellent sorption performance, as well as simple synthesis method and low-cost and environmentally friendly CS-based material make AOCS potentially applicable to uranium capture from seawater.