Fabrication and analysis of a highly hydrophobic and permeable block GO-PVP/PVDF membrane for membrane humidification-dehumidification desalination

Membranes with high hydrophobicity and moisture permeability are highly desired for preventing membrane wetting in membrane distillation type seawater desalination. To solve the membrane wetting problems and maintain high moisture permeability simultaneously, a new block composite membrane (GO(sic)PVP(sic)GO) was prepared by connecting graphite oxide (GO) sheets to polyvinylpyrrolidone (PVP). First, octadecyl amine (ODA) was functionalized with GO to form a micro/nanoscale hierarchical structured surface. Then, it was mixed with a PVP solution to form a new block composite membrane. Finally, the membrane was modified by low-surface-energy hexadecyltrimethoxysilane (HTEOS). At the suitable ratio of GO and PVP, the optimal arrangement of GO nanosheets was obtained, achieving the highest vapour permeation. Then, the structural parameters and moisture permeability of the novel membrane were analysed and characterized. Desalination with real seawater from South China Sea coast was performed. Compared to the virgin PVDF membrane, the novel membrane shows a similar permeability but a much higher hydrophobicity with the contact angle of 145.2 degrees and a more negative zeta potential. The new membrane can significantly reduce the adsorption of negative proteins. It exhibits excellent outstanding salt rejection with high flux, when used to desalinate real coastal seawater. The present membrane may be useful for improving the seawater desalination efficiency.