Efficient thorium(IV) removal by two-dimensional Ti2CTx MXene from aqueous solution

Abstract

A new group of two-dimensional (2D) materials known as MXene has induced great interests in water purification due to their hydrophilic surface and abundant functional groups. Herein, the performance of 2D Ti2CTx MXene material for thorium (Th(IV)) removal is evaluated in detail. Under different storage conditions, Ti2CTx in hydrated form (Ti2CTx-hydrated) exhibits great enhancement in sorption capacity compared to the dry counterpart, mainly due to the larger interlayer space and the easier entry and diffusion of Th(IV) ions. Batch sorption of Th(IV) onto Ti2CTx-hydrated reveals that the sorption process follows the pseudo-second-order kinetic model and Freundlich isothermal adsorption model. The maximum adsorption capacity can reach as high as 213.2 mg g−1 for Ti2CTx-hydrated, much higher than that of most common inorganic sorbents. Moreover, Ti2CTx-hydrated has excellent adsorption selectivity towards Th(IV) in the presence of competing metal ions. Scanning electron microscopy coupled with energy-dispersive spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy analysis are performed to characterize the morphology and structure of Ti2CTx before and after the adsorption, and mechanism for Th(IV) removal is proposed to be associated with inner-sphere complexation. The present results illustrate that Ti2CTx-hydrated could serve as a promising candidate for thorium preconcentration and separation.