Preparation of lignin surface-functionalized MXene nanosheets and its U(VI)adsorption properties

In order to further improve the adsorption performance of MXene nanomaterials on U(VI) in simulated radioactive wastewater, the surface functionalization of MXene was carried out by using natural resources of enzymatically hydrolyzed lignin (EHL) as a biosurfactant, and the materials before and after the modification were characterized and analyzed by using SEM-EDS, XRD, and FTIR, and the effects of pH, temperature, and the adsorption experiments were explored, reaction time, interfering ions and different initial U(VI) concentrations on the effect of U(VI) removal. The results show that EHL prevents the re-stacking of MXene nanosheets and introduces a large number of active functional groups, which improves the adsorption performance of EHL-functionalized MXene nanosheets. The maximum adsorption capacity for U(VI) is 231.95 mg·g⁻¹ at the mass ratio of MXene to EHL of 1∶5, the dosage of 0.1 g·L⁻¹, pH=5, and the temperature of 303 K. In addition, the adsorption kinetic and isotherm analyses show that the proposed second-order kinetic model and the Freundlich isotherm model fit this adsorption process well, and the thermodynamic analyses indicate that its adsorption process is spontaneous heat absorption. After five cycles of regeneration, the removal rate of U(VI) is still above 80%. Characterization results reveals that the interaction mechanisms between MX/EHL and U(VI) involve ion exchange, electrostatic attraction, and complexation with oxygen-containing functional groups. Based on this study, MX/EHL has great potential as an environmentally friendly adsorbent material for the removal of U(VI) from wastewater.