Janus membrane with fluorinated graphene oxide embedded PVDF-HP hydrophobic layer for efficient oil/water separation

Abstract

The efficient and low-cost treatment of oily wastewaters has become a concerned issue for mitigating the environmental pollution and reducing resource wastage. In this study, a novel Janus membrane was fabricated by electrospinning a thin hydrophobic layer of fluorinated graphene oxide (FGO) nanosheet-incorporated poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) nanofibers on the surface of a polyacrylonitrile (PAN) hydrophilic layer. The hydrophobic layer was controlled to be 15 times thinner than that of the hydrophilic layer by regulating the electrospinning time. The incorporation of FGO nanosheets into PVDF-HFP nanofibers induced the formation of numerous microspheres and finer nanofibers on the hydrophobic layer, thereby endowing the membrane with a high surface roughness with a “beads-on-strings” morphology. The PVDF-HFP/FGO hydrophobic layer exhibited a water contact angle of 136.8°, which contributed to a high oil flux of ~17500 L/m2.h and separation efficiency of 95.3% for the heavy oil/water mixture. In contrast, the membrane achieved a water flux of ~5800 L/m2.h and separation efficiency of 99.1% for the light oil/water mixture. The membrane could maintain stable performance over seven consecutive separation cycles and within the temperature range of 20–120°C. The prepared membrane could be considered as a promising alternative for the practical treatment of oily wastewaters.