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A novel polyvinyl alcohol-carbon nanotube containing an imidazolyl ionic liquid/chitosan composite hydrogel (termed CBCS) was prepared for highly selective uranium adsorption from seawater. The results show that CBCS has good adsorption properties for uranium within the pH range of 5.0-8.0. Kinetics and thermodynamics experiments show that the theoretical maximum adsorption capacity of CBCS to U(VI) is 496.049 mg/g (288 K, pH = 6.0), indicating a spontaneous exothermic reaction. Mechanism analysis shows that the hydroxyl group, amino group, and CN bond on the surface of CBCS directly participate in uranium adsorption and that the dense pores on the surface of CBCS play an important role in uranium adsorption. The competitive adsorption experiment shows that CBCS has excellent uranium adsorption selectivity. In addition, CBCS exhibits good reusability. After five adsorption-desorption cycles, the uranium adsorption rate of CBCS can still reach >98 %. Hence, CBCS has excellent potential for uranium extraction from seawater., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Land-based uranium resources are becoming scarce because of the widespread development and use of nuclear energy. Therefore, to make up for the shortage of uranium resources, a new chitosan/carboxymethyl- β -cyclodextrin/quaternary ammonium salt–functionalized amidoxime carbon adsorbent (CSAOCF) was designed and synthesized for extracting uranium from seawater. Experimental studies show that the adsorption of uranium by CSAOCF is a spontaneous endothermic reaction and chemical adsorption. The theoretical maximum adsorption capacity of uranium can reach 726 mg/g at 308 K and pH = 6. Moreover, the adsorption efficiency and selectivity of CSAOCF for uranium were significantly improved after the introduction of the carboxymethyl group, and the selection and partition coefficient of CSAOCF for uranium and vanadium increased from 16-fold to 30-fold under the same conditions. This indicates that there is a synergistic effect between carboxyl and amidoxime groups, which can promote the adsorption of uranium by CSAOCF. Furthermore, CSAOCF exhibits good oil resistance and can be reused more than five times. Therefore, CSAOCF containing carboxymethyl and amidoxime functional groups can considerably improve the selective adsorption of uranium and has great potential in the extraction of uranium from seawater. [Display omitted] • Synergistic effect of carboxymethyl and amidoxime groups enhances U adsorption, and the theoretical q m can reach 726 mg/g. • AO-adsorbent containing carboxymethyl group has a 30-fold higher K d for U than for V. • Under the pollution condition of 20 % oil content, the adsorption rate of uranium only decreases by 3.8 %. [ABSTRACT FROM AUTHOR]