Influence of graphene oxide's characteristics on the fabrication and performance of crosslinked nanofiltration membranes

Graphene oxide (GO) is emerging as an excellent next generation material for water purification membranes. Its ability to be fabricated cost-effectively in large quantities and featured characteristics, such as hydrophilicity, makes it an equitable graphene alternative in respective nanometric applications, including nanofiltration. In this study, the influence of key properties of the GO sheets, such as lateral size, surface chemistry and colloid stability, on the successful fabrication and subsequent water purification performance of crosslinked nanofiltration membranes is analysed. GO water suspensions with nanosheets of different lateral sizes and distribution of oxygenated functional groups were prepared by controlling the sonication time (from 0 to 180 min) starting from commercial GO. The variation of the physicochemical characteristics of the resulting GO sheets was comprehensively studied by means of atomic force microscopy, UV–Vis absorption spectroscopy, zeta potential measurements and X-Ray photoelectron spectroscopy. The morphology of the subsequently fabricated membranes was hereafter examined via scanning electron microscopy, while their nanofiltration performance was investigated against methylene blue solution. The influence of GO's physicochemical characteristics on membrane performance was apparent, with the average rejection values ranging from 59.8% to 98.4% at a changing lateral size and surface chemistry.