Surface charge engineering for two-dimensional Ti2CTx MXene for highly efficient and selective removal of cationic dye from aqueous solution

Abstract

• Few-layer Ti 2 CT x was synthesized by selective etching and ultrasonic exfoliation. • Ti 2 CT x showed excellent adsorption selectivity towards methylene blue removal. • The maximum adsorption capacity could reach as high as 2460.9 mg g −1 . • The primary adsorption mechanism was associated with electrostatic interaction. Exploring versatile materials that efficiently adsorb pollutants from wastewater is of critical importance for environmental remediation. As an emerging 2D material, MXene features a hydrophilic surface with abundant oxygen-containing groups that render a negatively charged surface, implying its great potential for removing cationic pollutants from wastewater. Given its remarkable properties, a novel Ti 2 CT x MXene as an adsorbent is synthesized through selective etching of Al layer from Ti 2 AlC and then ultrasonic exfoliation. The adsorption studies indicate that Ti 2 CT x exhibits highly efficient methylene blue (MB, cationic dye) removal performance, the maximum adsorption capacity can reach as high as 2460.9 mg g −1 , which is considerably higher than the values of graphene (83.2 mg g −1 ) and anionic dye removal (methyl orange, 122.6 mg g −1 ). Furthermore, the adsorption behavior fits well with the pseudo-second-order kinetic and Langmuir isotherm models, and thermodynamic analysis indicates that the adsorption is spontaneous and endothermic. Based on scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Fourier transform infrared spectra analysis, the principal adsorption mechanism is related to the electrostatic interaction between Ti 2 CT x and MB molecules. Meanwhile, the result is also confirmed by adsorption experiments at different pH values and background ions. This work shows that the MXene family materials can be applied as high efficiency adsorbent for removing cationic dyes from wastewater.