Ultrafast strategy to self-assemble polyamidoxime PVA nanofibers with solar-induced synergy for enhancing uranium extraction from seawater

Application of amidoxime (AO) based fibrous adsorbents in uranium extraction from seawater (UES) is hampered in their adsorption performance and preparation process, including two items: firstly, low grafting kinetics of monomer acrylonitrile (AN) and large amount of its homopolymers, secondly, low extraction efficiency limiting by the ultralow concentration of uranium and temperature of seawater. Herein, an ultrafast strategy to prepare AO based nanofibers (NFs) with polyvinyl alcohol (PVA) super hydrophilic slit nanopore structure via radiation crosslinking and grafting polymerization (c-PVA-g-PAO NFs) was designed. Combined with hydrophilic 2D MXene nanosheets for excellent photothermal and photoelectric synergistic assistance, further improved the adsorption performance of the material (c-PVA-g-PAO&MXene NFs). Super hydrophilic PVA NFs with water-resistant three-dimensional network structure generated by radiation crosslinking realized ultrafast graft polymerization of AN. Within 1 min AN can be grafted throughout the c-PVA NFs in its aqueous solution with degree of grafting (DG) 73.71%, and construct a well-developed slit nanopore structure inside and outside of the fiber. Through ultrasound, MXene can be effectively loaded on the surface of the nanofiber, and further enhance 30.16% of the adsorption capacity of the material under light with MXene content 8 wt%. The c-PVA-g-PAO&MXene NFs achieved adsorption capacity of uranium with 2.23 mg/g in natural seawater for 1 week, which increased 26.70% than in dark (1.76 mg/g). And it could undergo at least 5 cycles of adsorption and elution. This novel strategy with ultrafast grafting, facile operating process and solar-induced synergy provided a new ideal to promote the industrialization process of UES.