Construction of superhydrophilic hierarchical polyacrylonitrile nanofiber membranes by in situ asymmetry engineering for unprecedently ultrafast oil-water emulsion separation

Oily wastewater caused by the increment of industrial wastewater discharge and frequent oil spills endangers organisms and the environment seriously. Membrane separation technology is an efficient way to remove oil from various oily wastewaters, however the lack of highly permeable and anti-fouling membranes has hampered its application worldwide. Here, we conceive a facile in situ hybridization hydrophilization and asymmetry engineering strategy to manufacture superhydrophilic hierarchical hydrolyzed polyacrylonitrile (PAN) nanofiber membranes for ultrafast separation of oil-in-water emulsion through the electrospinning technique. The hierarchical structures of nanofibers ensure the separation efficiency and reduce the mass transfer resistance of the membranes through tailoring the nanofiber structure. Interestingly, the multi-hydrophilic crosslinked network co-functionalized by several hydrophilic active oligomers significantly enhances the hydrophilicity and finely tailors the pore structure of the hydrolyzed PAN nanofiber membranes further. The well-designed nanofiber membranes exhibit n-octane-in-H2O emulsion permeances as high as 22 206 L m(-2) h(-1) bar(-1) and toluene-in-H2O emulsion permeances as high as 29 840 L m(-2) h(-1) bar(-1) with separation efficiency above 99.2%, outperforming most of the state-of-the-art membranes. More importantly, the nanofiber membranes exhibit excellent anti-fouling performance with flux recovery rate above 98% and irreversible fouling rate about 2%, showing strong promise in removing oil from the oil-in-water emulsion.