Tannic acid-metal complex modified MXene membrane for contaminants removal from water

Developing membranes with low rejection of salt ions and high rejection of contaminants is desirable for drinking water treatment and wastewater reuse. 2D material-based membranes are promising candidates, however, studies on developing 2D material-based membranes with low rejection of salt ions and high rejection of contaminants (including hydrophobic micropollutants) are rare. In the current study, we enhance the selectivity of the 2D MXene membrane by coating the membrane surface with tannic acid (TA)-metal complex layer. After the surface modification, the resulted membranes have reduced mean pore size and surface zeta potential, and increased surface hydrophilicity. The modified membrane shows high water permeability, low salt ion rejection, and much-enhanced contaminant (include model dye molecules and hydrophobic micropollutants) removal. For example, the water permeability and MgSO4 rejection of MXene-Fe membrane are 261.6 LMH-bar and 13.1%, respectively; and the membrane resistance to 4-hydroxybenzoic acid, cinnamic acid, and rhodamine B increased by 35-, 64, and 108-fold after the surface modification, respectively. Besides, the DLVO theory is applied to estimate the DLVO interaction energy between the contaminant and the membrane surface, the purpose is to understand the experimental membrane rejection results from an interaction energy perspective. We believe the modified membranes have the potential to be applied for drinking water treatment and water reuse, and this study proposes a new strategy for adjusting the selectivity of 2D material-based membranes.