Mxene As A Novel Material For Next Generation Desalination Membranes

Desalinated seawater is the primary source of drinking water in Qatar. Among all present desalination technologies, reverse osmosis (RO) has been demonstrated as one of the most feasible processes. However, the main limitation with RO and other membrane-based techniques is costly operation and maintenance associated with membrane scaling, fouling, and degradation. Advanced membranes that enable ultrafast permeation while maintaining good mechanical properties, are very important to facilitate both water purification and desalination technologies. Low-dimensional nanomaterials such as carbon nanotubes, cellulose nanocrystals and graphene oxide (GO) have been tested in membranes due to their good mechanical properties and amenable surface functionalization. Specifically, GO nanosheets have recently emerged as a new material for ultrathin, high-flux and energy-efficient sieving membranes due to GO's unique two-dimensional atomically thin structure, outstanding mechanical strength and good flexibility, as well as good dispersion in aqueous solutions. However, selectivity and stability of fully wetted GO membranes in cross-flow conditions has remained challenging and solubility of GO can also lead to membrane disintegration under operation conditions. Herein we present MXenes [1], a new class of 2D carbides, as new promising membrane materials for water desalination applications. For this purpose, Ti3C2-based MXene membranes have been prepared by a vacuum-assisted filtration technique. In order to detect the permeated ions and molecules, we have performed electrical conductivity measurements and UV-Vis analyses. The results have shown that MXene membranes are selective towards ions of different size/charge, such as Cu2+, Mg2+, Na+, K+, SO42-, and Cl-. The permeation data have also shown a cut-off trend around 4 Å, and species of a larger size have been sieved out. The transport mechanism through MXene membrane films has been therefore size and charge selective due to the presence of the interlayer slit pores and the negative charges on the hydrophilic Ti3C2-based MXene film surfaces. In this study, we compare MXene membranes with GO membranes to better understand differences in their water desalination performance. Indeed these novel membrane composites are expected to improve the flux, increase the salt rejection efficiency and decrease adhesion of the adsorbed particulates and organic molecules, thus mitigating fouling. Reference: 1.M. Naguib, V.N. Mochalin, M.W. Barsoum, Y. Gogotsi, MXenes: A New Family of Two-Dimensional Materials, Advanced Materials, 26, 992-1005 (2014)