Reversible superwettability switching of a conductive polymer membrane for oil-water separation and self-cleaning

Abstract

Oil wastewater discharge, from both domestic and industrial sources, has caused serious environmental problems. Separation of stabilized oil-water emulsions and anti-fouling of membranes remain substantial global challenges. In this work, we fabricated a reversible superwetting sodium bis(2-ethylhexyl) sulfosuccinate-doped polypyrrole (PPy-AOT) membrane for separation of oil-water emulsions and alleviation of membrane fouling by self-cleaning. The PPy-AOT membrane exhibited super-hydrophobicity for water-removal and super-hydrophilicity for oil-removal in oxidation and reduction states, respectively. Results showed that the separation efficiency of the PPy-AOT membrane under oxidation and reduction states exceeded 80%. Moreover, the reduced PPy-AOT membrane with a super-hydrophilic surface showed underwater anti-fouling properties for viscous oils. Simultaneously, the membrane displayed outstanding acid resistance and salt tolerance. Based on density functional theory calculations, the reversible wettability switching of the PPy-AOT membrane was due to the reorientation of AOT anions during the redox process. Thus, the advantageous membrane properties, including reversible superwetting, high separation efficiency, and corrosion protection, show great potential for separation of oil wastewater.