Electrostatic self-assembly of nanoscale FeS onto MXenes with enhanced reductive immobilization capability for U(VI) and Cr(VI)

Herein, a MXenes decorated nanoscale FeS composites were developed via electrostatic self-assembly strategy to achieve efficient U(VI)/Cr(VI) adsorption-reduction. Different analytical techniques were applied to adequately characterize all as-prepared materials to determine the formation of species with the desired morphology and properties. Results revealed that the special chemical structure of MXenes could improve the dispersion of FeS nano-particles and suppress its aggregation. Meanwhile, the adsorption data closely well tailored with the Langmuir isotherm and Pseudo-second-order equation, and the maximum removal efficiencies were 88.5 and 107.2 mg/g for uranium(VI) and chromium(VI). It was also found that the presence of other cations and anions had no obvious influence on removal of U(VI)/Cr(VI), whereas the elimination process was a spontaneous endothermic reaction. More importantly, according to the spectroscopic analysis and DFT calculation, both FeS and surface functional groups on Ti3C2@FeS-PDA/PEI exhibited strong chemical affinities to the targeted pollutants, while FeS could effectively reduce Uranium(VI) to Uranium(IV) and Chromium(VI) to Chromium(III). This work facilitated the omnidirectional improvement of MXenes-based materials for the de-pollution of practical radionuclide or heavy metals wastewater.