Immobilizing nZVI particles on MBenes to enhance the removal of U(VI) and Cr(VI) by adsorption-reduction synergistic effect

How to efficiently remove and separate U(VI)/Cr(VI) have become an important environmental problem. In this study, a novel collaborative strategy for enhancing the removal of U(VI)/Cr(VI) was developed through loading nZVI into the inter-layer structure of MBenes, and results revealed that MBenes not only inhibited the oxidation of nZVI, but also effectively improved its reactivity. The maximum removal efficiencies were 107.8 and 68.6 mg/g for uranium(VI) and chromium(VI), which was higher than that of most reported materials. This work facilitated the omnidirectional improvement of nZVI-based materials for the depollution of practical radionuclide or heavy metals wastewater. [Display omitted] •A novel MBenes based adsorbent was successfully constructed.•MBenes could improve the dispersion and reactivity of bare nZVI.•Waterenvironment conditions played a vital role in adsorption of U(VI)/Cr(VI).•The removal process mainly dominated by the adsorptive and reductive reaction. Herein, a novel collaborative strategy for enhancing the removal of U(VI)/Cr(VI) was developed through loading nZVI into the inter-layer structure of MBenes. Spectroscopic analysis elucidated that MBenes not only inhibited the oxidation of nZVI, but also effectively improved its reactivity. Batch experiments showed that the removal rate of targeted pollutants by nZVI@MBenes was higher than that of nZVI or MBenes due to the increment of active sites and extension of interlayer space. With the aid of kinetics and isotherms, which manifested that the adsorption data were fitted for the Langmuir and Pseudo-second-order kinetic models. Meanwhile, nZVI@MBenes afforded the largest saturated capacity of 107.8 mg/g for U(VI) and 68.6 mg/g for Cr(VI). Synergistic adsorption-reduction occurred during the elimination process based on characterizationanalysis and DFT calculation. Namely, the targeted pollutants were rapidly adsorbed by the as-prepared composites via electrostatic interaction, then the surface-associated nZVI acted as an electron donor to reduce Cr(VI) to Cr(III) and U(VI) to U(IV). Thus, this work would open a new window for the practical application of nZVI-based materials in wastewater treatment.