Highly efficient self-cleaning of heavy polyelectrolyte coated electrospun polyacrylonitrile nanofibrous membrane for separation of oil/water emulsions with intermittent pressure

Abstract Electrospun polyacrylonitrile fiber membranes (EPFMs) are coated with multilayer films that assembled by layer-by-layer (LBL) technique through alternating deposition of polyallylamine hydrochloride (PAH) and polyacrylic acid (PAA). To obtain the heavy polyelectrolyte (PE) layer consisting of PAH and PAA, single pH value was replaced with alternative pH during LBL processes stabilizing the PAH/PAA layer without significant desorption. The heavy zwitterionic-like LBL coating of PAH/PAA film on the EPFM surface presents complete oil repellency while wetted in water (i.e., underwater superoleophobicity), so that allows to efficiently remove oil stains on dry EPFM by water. Removal of oil staining from a fibrous surface with high contact area demands to build up extremely strong bonding with water in both pristine and oil-wetted states. The PAH/PAA-coated EPFMs exhibit excellent self-cleaning from fibers even already wetted by oil. Generally, there is a maximum permeation volume during oil/water emulsion separation, because the blocked oil accumulates as a hydrophobic layer to block water passing through. These PAH/PAA-coated EPFMs are resilient to oil accumulation with intermittent pressure during the oil/water separation to remain the high permeation flux (over 30000 L m−2 h−1bar-1), still an pressing challenge in this area.