Two-dimensional Na-Bentonite@MXene composite membrane with switchable wettability for selective oil/water separation

MXene-based two-dimensional (2D) material membranes have attracted an increasing number of attentions in the field of separation and purification. However, the easily oil-pollution of MXene membrane still limit its further application for oil/water separation. In this work, Na-Bentonite was embedded into MXene nanosheets and then a series of [email protected] (NBM) composite membranes were prepared by one-step hydrothermal pretreatment and vacuum self-assembly on polyvinylidene fluoride membrane surface. The modified composite membranes exhibited excellent separation performances with a rejection ratio above 96 % and a flux recovery rate (FRR) higher than 86 % after 8 cycling tests for oil/water emulsion. In addition, the sandwich structure consisting of MXene nanosheets and Na-Bentonite could not only play a positive role in the stability of composite membrane, but also formed a special micro-nano structure on membrane surface, resulting in a switchable wettability of composite membrane. When the membrane surface was pretreated with water or oil, it presented hydrophilic/hydrophobic or hydrophobic/oleophilic surfaces, respectively, which realized the effective separation for different components in oil/water emulsion. This work provides a new method for the design and construction of MXene-based 2D membrane with continuous anti-fouling capacity, which shows a great application potential in the treatment of oily wastewater.