Facile fabrication of nanofiber- and micro/nanosphere-coordinated PVDF membrane with ultrahigh permeability of viscous water-in-oil emulsions

To achieve highly efficient purification of emulsified oil, a superhydrophobic, superoleophilic and under-oil superhydrophobic poly(vinylidene fluoride) (PVDF) nanofibrous membrane was developed through a facile electrospinning strategy. The PVDF nanofibrous membrane exhibited a synchronous combination of nanofibers and micro/nanospheres, which was produced by solely controlling the PVDF concentration of the electrospun solutions. The fabricated PVDF nanofibrous membrane exhibited a water contact angle of 152 degrees +/- 2 degrees, oil contact angle of 0 degrees in air and under-oil-water contact angle of 152 degrees +/- 1 degrees due to the inherently low surface energy and unique structures composed of nanofibers and micro/nanospheres. Thanks to the under-oil superhydrophobicity, hierarchical structure and high porosity (similar to 95%), the composite membrane showed extremely high permeability of 88166 +/- 652 L m(-2) h(-1) bar(-1) with separation efficiency higher than 99%, which was few orders of magnitude higher than the previous findings. Moreover, the nanofibrous membrane exhibited robust continuous separation, indicating its scalable application for purifying emulsified oil.