Highly efficient removal of rare earth elements by two-dimensional titanium carbide nanosheets as impacted via water...

The separation and recycling of rare earth elements (REEs) are very important owing to the high demand, limited resource, specific usages, and environmental issues. In this work, two-dimensional Ti₃C₂T_x MXene was introduced to remove REEs (Nd(III) and La(III)) from water, and its physicochemical properties were conducted by HRTEM, SEM-EDS, XRD, FTIR, and XPS. Various parameters, such as initial pH, REEs initial concentration, contact time, and temperature, were investigated by batch experiment, respectively. Furthermore, the adsorption kinetic and isotherm were examined to analyze the adsorption behavior and adsorption mechanism. Nd(III) and La(III) have a good affinity with Ti₃C₂T_x MXene surface functional groups (-F, -OH, and containing oxygen groups). The maximum adsorption capacities of Ti₃C₂T_x MXene for Nd(III) and La(III) were 229.85 mg/g and 175.83 mg/g at T = 333 K, respectively. The adsorption data of Nd(III) on Ti₃C₂T_x MXene fitted well with the Freundlich isotherms model and pseudo-second-order kinetic model. However, the best fitting for La(III) adsorption on Ti₃C₂T_x MXene was described by both pseudo-first-order and pseudo-second-order model. Thermodynamic study of Nd(III) and La(III) adsorption on Ti₃C₂T_x MXene showed that the reaction was a spontaneous and endothermic process. These results indicated Ti₃C₂T_x MXene had a great potential in extracting REEs from an aqueous solution.