Enhancing demulsification efficiency and sustaining constant separation flux in oil/water emulsions via Janus membrane inspired by spider silk

Conventional special wettable membranes for the separation of the surfactant-stabilized oil/water emulsions primarily rely on the "size-sieving" mechanism, which enhances efficiency by reducing the pore size, leading to a trade-off between separation flux and efficiency. Inspired by spider silk, we developed a novel Janus membrane (JPSPP) capable of high demulsification capacity and constant separation flux. This membrane combines a superhydrophobic PS@PDMS membrane (PPM) with spindle-knotted structures on a negatively charged superhydrophilic PAN@SAS membrane (PSM) through electrospinning. The synergy of electrostatic force generated by charged surfaces, the Laplace pressure created by spindle-knotted geometry, and the wettability gradient resulting from asymmetric wettability enhance the demulsification capacity. The high and constant separation flux was achieved as Laplace pressure drives rapid coalescence of demulsified oil droplets towards the top of the spindle-knotted structures, facilitating oil detachment and efficient water permeation downward. As a result, the JPSPP membrane achieved a separation efficiency exceeding 99.9 %, with a constant separation flux of up to 1952.27 L m(-2) h(-1), representing a 3-4 folds improvement compared to the pure PAN membranes (PM). The separation performance of the JPSPP still maintains excellent separation performance with efficiency above 98.3 % and a slight attenuation in flux after twenty filtration cycles. The research proposes groundbreaking solutions that significantly enhance the demulsification efficiency and maintain a constant separation flux for oil/water emulsions, with the potential to profoundly impact multiple industries including food processing, energy production, and the petroleum industry, etc.