Effect of ionic liquid on the structure and desalination performance of PVDF-PTFE electrospun membrane

The relatively large pore size of electrospun membranes might limit their application for direct contact membrane distillation (DCMD). Incorporation of ionic liquid is a potential approach to decrease the pore size of electrospun membranes, which was attributed to the increased conductivity of electrospinning solution. In this study, a novel nanofibrous membrane based on the blends of poly(vinylidene fluoride) (PVDF), polytetrafluoroethylene (PTFE) and ionic liquid (BMIMPF₆) was fabricated and applied for the DCMD. The effects of the BMIMPF₆ on the morphology, pore size and DCMD performance of the PVDF-PTFE nanofibrous membrane were investigated. Compared with neat (PVDF-PTFE) membranes (average pore size: 0.93 μm), the incorporation of BMIMPF₆ resulted in a smaller mean pore diameter (0.58 μm). The liquid entry pressure value of the modified composite membrane also increased from 62.75 kPa (neat) to 83 kPa, due to the decreased pore size. The composite membrane exhibited a longer lifespan (about 26 h) than neat membrane during long-term DCMD process, which makes this composite membrane a promising candidate for DCMD application. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48467.