One-step preparation of tubular nanofibers and micro/nanospheres covered membrane with 3D micro/nano structure for highly efficient emulsified oil/water separation

Facile fabrication of superwetting materials is urgently desired, which remains a challenging issue for industrial oily wastewater treatment. In this study, a novel tubular nanofibers and micro/nanospheres covered PVDF/graphene (GE) composite membrane (TPGCM) was prepared via one-step simultaneous electrospinning/electrospraying process with the polyethylene terephthalate (PET) braided tube (BrT) as the support. This simple combined technique allowed the uniform integration of PVDF micro/nanospheres and GE nanosheets into the PVDF nanofibrous network to form a 3D hierarchical micro/nano structural composite membrane. The resultant membrane exhibited superoleophilicity in air with oil contact angle of 0°, and showed under oil superhydrophobicity with corresponding contact angle of 159 ± 0.8°. Furthermore, the morphology of the covered micro/nanospheres was simply controlled by adjusting GE nanosheets content in electrospraying precursor. As-prepared TPGCM can effectively separate a series of Span-80-stabilized water-in-oil emulsions, which showed outstanding separation efficiency of up to 99.8 %. Moreover, the robust recyclability was also presented with separation efficiency of more than 99.3 % after 10 cycles. Our strategy possesses the advantages of simplicity and cost saving, avoiding complicated reaction or post treatment, thus indicating its scalable application for practical oily wastewater purification.