Covalently Crosslinked Sulfonated Graphene Oxide Membranes for Alleviation of Silica Scaling and Organic Fouling for Brine Treatment by Pervaporation

Abstract

Sulfonated graphene oxide (SGO) crosslinked with polyvinyl alcohol (PVA) membranes were tailored to ensure excessive resistance to silica scaling and organic fouling as well as ultrafast water transport without compromising salt rejection. The synthesized SGO showed a smoother surface morphology, improved zeta potential, and a higher hydration capacity than graphene oxide (GO). Further intercalation of PVA through glutaraldehyde crosslinking, confirmed by Fourier transform infrared and X-ray photoelectron spectroscopy, increased the cohesiveness of SGO and thus managed to withstand ultrasonication tests without any erosion of the coating layer. The surface hydrophilicity of SGO decreased after PVA crosslinking. However, permeate fluxes were comparable before and after crosslinking with increased salt rejection after crosslinking, attributable to the presence of a plethora of nanochannels formed by the tight stacking of SGO. The pervaporative desalination test revealed that covalently crosslinked SGO exhibits 64 kg m-2 h-1 of permeate flux with an extraordinary salt rejection of 99.99% for a 10 wt% NaCl feed solution at 65 °C. The 72 h-long organic fouling and silica scaling tests proved that the SGO crosslinked with PVA sustains a stable flux with less silica scaling and organic fouling than the crosslinked GO, attributable to the hydrogen bonding energy and dense surface negative charges caused by sulfonic acid. To conclude, the PVA crosslinked SGO membrane carries superlative advantages for long-term brine treatment by pervaporation related to its ability to withstand silica scaling and organic fouling.

Keywords: Pervaporation, Desalination, sulfonated graphene oxide, silica scaling, organic fouling