CF4 plasma-modified superhydrophobic PVDF membranes for direct contact membrane distillation

•Preparation of superhydrophobic membranes for membrane distillation.•Superhydrophobic membranes showed higher water flux than virgin ones.•Flux enhancement mechanism proposed.

High performance superhydrophobic PVDF flat sheet membranes for direct contact membrane distillation (DCMD) were prepared via CF4 plasma surface modification. The performance of the virgin and CF4 modified membranes was examined using sodium chloride solution (4 wt%) as feed in a DCMD process. Results reveal that CF4 surface modification yielded superhydrophobic membranes (water contact angle: 162.4°) with about 30% higher water flux than the virgin PVDF membrane. The underlying mechanism that leads to the significant improvement in membrane performance was investigated in detail with respect to membrane morphology, gas permeability, liquid entry pressure, and contact angle measurements. Results indicate that the combination of increased gas permeability and superhydrophobicity contributes mostly to the improved water flux.