Engineering electrified hydrophobic membranes toward superior fouling resistance

Electrified membrane is considered an alternative solution to the trade-off between permeability and fouling/wetting resistance of hydrophobic membranes. Herein, we reported a facile and universal carbon nanotubes (CNT)-based surface coating methodology followed by crosslinking with polyvinyl alcohol (PVA) toward robust electrified hydrophobic membranes. The physicochemical properties including sheet resistance of the as-prepared membranes were scrutinized over a varying mass loading of the CNT and PVA. Serving as the cathode in membrane distillation (MD), the CNT-modified membrane exhibited excellent anti-oil-fouling performance against hexadecane-in-water emulsions of 500 ppm in addition to an improved water vapor flux against brackish water regardless the substrate membrane. In particular, at a cell potential of 3 V, the fouling constant for electrified membrane was reduced up to 100 % compared to the control, with a negligible flux decline by only 4 %. Such a data was in line with the membrane-foulant interactive energy analysis, indicating the significance of the enhanced electro-repulsion with the cell potential applied. Interestingly, the fouling-resistance of polytetrafluoroethylene membrane was significantly improved to a comparable level with the other counterparts, as illustrated by the electrochemical impedance spectroscopy data. This study confirms that the CNT-modification together with an electro-assistance paved the way for electrified hydrophobic membrane of superior fouling resistance.