Facile preparation of PVDF-HFP/GE tubular nanofiber membranes with 3D surface structure for high efficient continuous oil/water emulsion separation

Polymeric membranes show great potential for treating wastewater containing oil/water emulsions, which can cause serious environmental pollution. In this paper, novel polyvinylidene fluoride-co-hexafluoropropyle/graphene (PVDF-HFP/GE) tubular nanofiber membranes (TNMs) were fabricated by electrospinning and thermal treatment. The prepared TNMs were post-treated under different thermal treatment conditions to obtain 3-dimensional (3D) structures. The effects of thermal treatment time and temperature on membrane structure and performance were investigated by field-emission scanning electron microscopy, hydrophobicity, pore size and distribution, porosity, and liquid entrance pressure. After thermal treatment, more graphene was exposed to the membrane surface, which provided excellent oil/water selective wettability and anti-fouling performance. In addition, the thermally treated TNMs possessed an optimal pore structure and could separate surfactant-stabilized water-in-oil emulsions at high filtration rates (497.5 ±13.3 L·m−2·h−1) and separation efficiency (>99%). Moreover, the filtration rate and separation efficiency remained constant over 10 filtration cycles, showing that these membranes have great potential for application to practical oil/water separation processes.