Robust preparation of braid-reinforced hollow fiber membrane covered by PVDF nanofibers and PVDF/SiO2 micro/nanospheres for highly efficient emulsion separation

The PVDF nanofibers and the PVDF/silica (SiO2) micro/nanospheres were deposited simultaneously on the outer surface of a rotating PVDF braided tube by electrospinning and electrospraying to fabricate a new type of enhanced hollow fiber membrane. By adjusting the content of SiO2 in electrospraying solution, the micro/nanospheres with different morphology were obtained to optimize the performance of the prepared membranes. When 2 wt% SiO2 was added, the deposited micro/nanospheres mainly took loose porous PVDF aggregates as the skeleton and SiO2 particles as the filler to construct the micro/nano structure on the membrane surface like that on the lotus leaf surface. Therefore, the membrane surface exhibited superoleophilicity (theta(o) = 0 degrees) and underoil superhydrophobicity (theta(uow) = 154 degrees). In addition, the deposited micro/nanospheres can effectively weakened the stacking between the deposited nanofibers. The resultant membrane not only had the high permeability with pure oil flux of 8557 Lmiddotm(-2)middoth(-1), but also possessed the excellent oil-water separation performance with separation efficiency of 99.70%. Meanwhile, it also showed the outstanding tensile strength of 79.40 MPa. The preparation method was simple and easy to operate, which would provide more possibilities for the preparation of hollow fiber membranes with efficient separation performance to the water-in-oil emulsion.