Pressure-triggered piezoelectric membrane-mediated interfacial demulsification toward high-efficiency emulsion separation and dynamic antifouling

Oily wastewater discharge poses significant challenges for ecological environments and public health. Conventional antifouling membranes primarily rely on passive size sieving and wettability regulation, while lacking the ability to actively modulate emulsion interfacial stability during filtration. In this work, by integrating nonsolvent induced phase separation (NIPS) with sequential electrostatic assembly, we developed a polyethyleneimine/poly (sodium 4-styrenesulfonate) (PEI/PSS)-modified MoS 2 /PVDF piezoelectric membrane (PPMP) that realizes pressure-triggered interfacial demulsification toward improved emulsion separation efficiency and dynamic antifouling ability. The incorporation of MoS 2 promotes the formation of the electroactive β-phase in PVDF and enhances the pressure-responsive electrical output, while the PEI/PSS coating improves membrane interfacial wettability. Under pulsed pressure filtration, the PPMP membrane generates continuous piezoelectric voltage outputs and exhibits excellent separation performance toward sodium dodecyl sulfate (SDS)-stabilized O/W emulsions and significantly improved antifouling performance. Mechanistic analysis reveals that the pressure-triggered piezoelectric field perturbs the surfactant-stabilized interfacial film, weakens emulsion stability, and promotes droplet polarization and coalescence. The resulting enlarged droplets are less likely to penetrate membrane pores and more readily detached from the membrane surface under the combined action of piezoelectric-field-induced interfacial effects and hydrodynamic forces. These coupled effects improve emulsion separation efficiency and mitigate membrane fouling. This work provides a promising strategy for designing stimuli-responsive piezoelectric membranes for efficient emulsion separation and antifouling performance in oily wastewater treatment.