Roughness-enhanced hydrophobic graphene oxide membrane for water desalination via membrane distillation

Novel design of hydrophobic membrane could improve the efficiency of membrane distillation (MD) technology. Owning to being easy to realize hydrophobic modification, fast radial heat transfer rate and limiting the passage of larger contaminants, hydrophobic graphene oxide (GO) membrane shows potential for MD process. In this work, we reported on a new type of nanoparticles intercalated GO membrane with hydrophobic surface for MD application fabricated by vacuum-filtration method. The introduction of nanoparticles (SiO2) by physical mixing enhanced the surface roughness of GO membrane. A subsequent grafting of long alkyl chains (hexadecyltrimethoxysilane) further increased the membrane hydrophobicity. The effects of treating temperature and nanoparticles content on the membrane nanostructures, surface hydrophobicity and desalination performance were systematically investigated. The optimized membrane annealed at 80 °C with hydrophobic surface (water contact angle: 120.8°) exhibited water flux of 13.59 kg m-2 h-1 and salt rejection of 99.99% under 60 °C for 35 g L-1 NaCl in water during vacuum MD process. Besides of the expected gradually higher water flux at elevated temperature, such excellent desalination performance remains stable by varying the salt concentration or adding model foulants such as surfactant sodium dodecyl sulfate and organic humid acid in the feed.