Piezoelectric PVDF membranes for emulsion separation with constant flux and high efficiency†

Emulsion separation, a focal and challenging aspect of oil–water separation processes, has long been a source of frustration for researchers due to the phenomenon of flux decline caused by concentration polarization and adhesion of oil droplets during the separation process. Attempts have been made to address membrane fouling issues through catalytic degradation and bubble flotation methods; however, the flux decline phenomenon persisted. In this work, during the fabrication process, intermolecular forces were utilized to polarize polyvinylidene difluoride molecular chains to increase the β-phase and endow them with piezoelectric properties. The prepared piezoelectric membrane, under the variable pressure environment created using a peristaltic pump, could maintain stable flux throughout the separation process without decline while maintaining high separation efficiency, as opposed to constant pressure filtration. It was found that the main mechanism of action was dielectrophoretic forces, and the feasibility was theoretically analyzed, showing promise for the extension to the separation of a greater variety of oil-in-water emulsions. Additionally, the piezoelectric catalytic effect could generate reactive oxygen species, which could further degrade organic pollutants to alleviate membrane surface contamination and blockage, further maintaining flux. This work provides new insights into the development of emulsion separation applications.