Highly Oriented Nanofiber Membrane with Efficient Demulsification and Dynamic Antifouling for Emulsion Separation via the Piezoelectric Effect

Herein, a hydrolyzed polyacrylonitrile (PAN) nanofiber membrane with highly oriented structure (designated as HOFM) is fabricated for in situ dynamic fouling control during oil-in-water (O/W) emulsion separation. This membrane possesses piezoelectric properties, capable of inducing sustained negative charges and generating an open-circuit output voltage of 6 V under a pulsed pressure of 10 kPa. During filtration, the inherent pulsed hydraulic pressure is converted into pulsed voltage, thereby constructing a dynamic electric field. Both experimental results and molecular dynamics simulations verify that this dynamic electric field not only facilitates the deformation, collision, and coalescence of emulsified oil droplets to accelerate demulsification significantly but also mitigates the adsorption and deposition of negatively charged oil droplets on the membrane surface via electrostatic repulsion, thus effectively alleviating membrane fouling. Benefiting from this piezoelectric effect, the HOFM exhibits a stable permeation flux of approximately 4000 L m –2 h –1 bar –1 and maintains a separation efficiency exceeding 97% for SDS surfactant-stabilized O/W emulsions during long-term continuous separation, exhibiting application potential in wastewater treatment. This work combines the piezoelectric self-powered property with membrane separation technology, providing a strategy for efficient and eco-friendly oil–water separation.