Enhanced photocatalytic extraction of the g-C3N4 NTs in situ co-grafted carbonyl and amide oxime groups for uranium from seawater

Uranium as “food” for nuclear energy plays an indispensable role in the sustainable development of the nuclear industry and is a strategic resource. With the increasing scarcity of uranium resources on land, extracting uranium from the ocean is one of the ways to solve the shortage of uranium resources. The adsorption methods have been more attention in the technology of uranium extraction from seawater. However, the adsorption capacity of various adsorbents which have been widely studied is far from the target of practical application. The g-C₃N₄ as an excellent and easy to obtain photocatalyst has been widely concerned. The coupling effect of photocatalysis and adsorption may be one of the effective ways to improve the adsorption capacity of uranium extraction from seawater. In this paper, the amidoxime (AO) and carbonyl (C=O) as a dual-functional groups were in situ grafted to g-C₃N₄ NTs to optimize the electronic structure and chemical active for photocatalytic adsorption of uranium extraction from seawater. The results of performance test demonstrated that the uranium adsorption capacity reached 512.46 mg·g −1 with C=O-AO/g-C₃N₄ NTs powders under simulated sunlight irradiation and the recovery efficiency of the modified absorbents was over 92 % from simulated sea water. The adsorption process mechanism analysis results proved that photogenerated electrons intensified by introduced C O groups capture to reduce UO₂ 2+ ions preferentially chelated by AO groups of C=O-AO/g-C₃N₄ NTs to hydrated quadrivalent peroxide uranyl species under oxygen-rich conditions.