Magnetic amidoxime-functionalized MXenes for efficient adsorption and immobilization of U(VI) and Th(IV) from aqueous solution

Herein, Fe₃O₄ nano-particles were integrated into the interlamellar spacing of amidoxime-functionalized Ti₃C₂ to construct a novel magnetic MXenes based composites (Fe₃O₄@Ti₃C₂-PDA/OA), and applied to removal radionuclides from the simulated radioactive wastewater. The physico-chemical properties of the surface functionalized MXenes were probed using advanced spectroscopy techniques, while batch experiments were conducted to investigate the influence of pH value, contact time and coexisting pollutants on enrichment of U(VI)/Th(IV). The experimentally determined the maximum adsorption amounts for U(VI) (pH = 5.0) and Th(IV) (pH = 3.0) on Fe₃O₄@Ti₃C₂-PDA/OA were 165.9 mg/g and 202.7 mg/g, which were much larger than the traditional adsorption materials. Meanwhile, the well-modeled results of isotherm and kinetics data demonstrated that elimination of the two radionuclides were a monolayer and chemisorption process, whereas the calculation of thermodynamic data indicated that the adsorption was a spontaneous and endothermic process. The spectral analysis results revealed that the elimination mechanism was achieved through the complexation of hydroxyls and amidoxime groups anchored onto the skeleton of Fe₃O₄@Ti₃C₂-PDA/OA with U(VI)/Th(IV). This work provided a bright future for MXenes based composites in the application of remediation of radioactive ions.