Anti-biofouling amidoxime polyacrylonitrile composite fibers modified with phosphate and guanidine for efficient and selective uranium extraction from seawater

With the escalating demand for nuclear energy, conventional uranium reserves are being depleted, making uranium extraction from seawater a key research area. Therefore, the development of high-performance adsorbent materials is crucial. In previous studies, polyacrylonitrile-amidoxime polyacrylonitrile fibers (PAN-PAO) were fabricated via a wet-spinning technique. Building on this foundation, a novel composite fiber adsorbent, designated PAN-PAO-OH-B-T, was synthesized through hydrothermal modification using polyhexamethylene biguanidine (PHMB) and trisodium phosphate (TSP), thereby introducing amidoxime, guanidine, and phosphate functional groups. The PAN-PAO-OH-B-T fibers exhibited synergistic uranium binding enabled by the multiple functional groups, achieving a high adsorption capacity of 1350 mg/g and an elevated selectivity coefficient of 20.6. Adsorption kinetics followed a pseudo-second-order model, and equilibrium data were well described by the Langmuir isotherm, with a theoretical maximum capacity of 2058 mg/g. In terms of reusability, the fibers retained an adsorption capacity of 1310 mg/g with a desorption rate of 91.4 % after six successive cycles. Additionally, the incorporation of guanidine functionalities enhanced antibacterial properties, with a bacterial inhibition rate exceeding 90 %, and substantially reduced algal adhesion. After 28 days of exposure to natural seawater, the PAN-PAO-OH-B-T fibers achieved a uranium uptake of 9.66 mg/g, demonstrating significant promise for practical applications in seawater uranium recovery.