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In this study, the optimum spinning conditions were determined by orthogonal experiment, and polyamide oxime nanofibers (PAO NFs) with excellent morphology and adsorption were prepared by electrospinning oxime solution. PAO NFs were characterized by SEM, FTIR, NMR and elemental analysis. The effects of time, solid–liquid ratio, pH, ionic strength, initial concentration and temperature on U(VI) adsorption on PAO NFs were studied. U(VI) adsorption on PAO NFs fitted well by the pseudo first/second-order kinetic model and Langmuir model with linear equation. The maximum adsorption was 118 mg/g. Uranyl ion was coordinated with oxime oxygen and amine nitrogen of the amidoxime group. PAO NFs is expected to extract uranium from seawater efficiently and economically. [ABSTRACT FROM AUTHOR]

[Display omitted] • Preparation of Alg/PAO microspheres by self-assembly crosslinking method. • U-adsorption of the microspheres was greatly enhanced via synergy of functional groups. • The adsorption mechanism of U(VI) on Alg/PAO microspheres was discussed by XPS spectra and DFT simulations. • Alg/PAO microspheres were owned good U-adsorption reusability. Highly efficient recovery of uranium from seawater is essential for the enormous global demand of nuclear fuel in the future. In this study a new Semi-Interpenetrating Polymer Network Alg/PAO (Semi-IPN Alg/PAO) hydrogel microspheres adsorbent (Abbreviated as Alg/PAO) was prepared by self-assembly method. This material has high uranium adsorption capacity (186.6 mg/g at room temperature), high adsorption selectivity, easy to manufacture on large-scale, facile to handle and collect in practical situations, which are essential for practical applications in the recovery of U(VI) from seawater. The effects of solid-liquid ratio, ionic strength, contact time, pH, initial concentration and temperature on the adsorption of uranium by Alg/PAO hydrogel microspheres were investigated by batch experiments. The U(VI) adsorption on Alg/PAO hydrogel microspheres fitted well to the pseudo second-order kinetic model and Langmuir model. FTIR and XPS and DFT (Density Functional Theory) simulations indicate that the uranyl ion mainly form chelates with amidoxime groups and carboxyl groups on sodium alginate with uranium. [ABSTRACT FROM AUTHOR]

• The copolymers with amidoxime and imidazole groups accelerated uranium adsorption. • The copolymers with amidoxime and imidazole groups remarkably enhanced adsorption capacity of U(VI). • The copolymers and U(VI) desorption with Na 2 CO 3 + H 2 O 2 could be reused. • The copolymers have a good selectivity for uranium. With the development of nuclear power and the depletion of uranium resources on land, extracting uranium from seawater has become a grand task. In particular, the synthesis of highly efficient and selective adsorbents becomes very important. Three copolymers (P(AO/C 2 VIM+Br−)-6, P(AO/C 6 VIM+Cl−)-3 and P(AO/C 12 VIM+Cl−)-2 were synthesized by radical polymerization, alkyl substitution and the amidoximation reaction of hydroxylamine. The copolymers were characterized by using FTIR, XPS, 1H NMR, and elemental analysis. The effects of different amount of imidazole cation and different length of branched chain on the adsorption were investigated by batch experiments, including solid-liquid ratio, contact time, pH, ionic strength, and coexisting ions. Meanwhile, the adsorption thermodynamics and kinetics of U(VI) on the copolymers were carried out. The results proved that the U(VI) adsorption by the copolymers strongly depended on ionic strength and pH, and fit well with pseudo–second-order model and Langmuir model and displayed endothermic, spontaneous process. Based on FTIR and XPS analysis, the possible binding mechanism involved uranyl with oxime O and amino nitrogen by bidentate coordination model or through bidentate coordination of oxime O, amino N and imidazole N. In addition, a little uranium might be adsorbed with positive charges by coulombic interaction, especially the adsorption of uranium on copolymer P(AO/C 12 VIM+Br−)-2. Finally, reuse performance of copolymers and adsorption of uranium in simulated seawater were studied comparatively. The results showed that P(AO/C2VIM+ Br−)-6 can be regarded as a good adsorbent for extracting uranium in simulating seawater. [ABSTRACT FROM AUTHOR]