Phytate-modified MOFs grown on carbon nanotubes for efficient adsorption of uranium(Ⅵ) from seawater

[Display omitted] •MOF was grown on multi-walled carbon nanotubes (NH2-MIL-101@MWCNT).•MWCNT significantly increased the specific surface area.•NH2-MIL-101@MWCNT was modified with phytic acid via Mannich reaction.•Excellent adsorption capacity of 599.77 mg·g−1 for uranium(Ⅵ).•Uranium (Ⅵ) removal rate up to 86.2% with high selectivity in natural seawater. The selective separation of uranium through adsorption remains a formidable challenge. Therefore, a one-step hydrothermal method was initially employed to anchor the metal-organic framework onto carbon nanotube oxides (NH2-MIL-101@MWCNT, the BET surface area of 1017.63 m2·g−1). Subsequently, a surface-functionalized composite nanoparticle (named PA-MIL-101@MWCNT, the BET surface area of up to 368.14 m2·g−1) was synthesized through phosphorylation via the Mannich reaction for uranium adsorption. Batch adsorption experiments unequivocally demonstrated that the modification with phytic acid led to a significant improvement in the uranium adsorption capacity of the composite material, achieving a maximum adsorption capacity of 599.77 mg·g−1. The initial adsorption rate of PA-MIL-101@MWCNT was exceptionally rapid, achieving 73.84 % of the maximum adsorption capacity within 10 min. Adsorption kinetics and thermodynamics indicated that uranium adsorption follows a single-molecule chemisorption mechanism. PA-MIL-101@MWCNT exhibits exceptional resistance to ionic interference within natural seawater, demonstrating excellent stability and recyclability. XPS and DFT calculations strongly supported the notion that the uranium adsorption mechanism was associated with the oxygen atoms in the PO and P-O functional groups. These findings suggest that PA-MIL-101@MWCNT can be considered an excellent material for uranium extraction from seawater, which is significant to the sustainable utilization of nuclear energy materials.