Highly crosslinked, chlorine tolerant polymer network entwined graphene oxide membrane for water desalination

Graphene and its derivatives are very attractive for constructing membranes for high-efficiency separation applications including water purification and desalination. To develop practical desalination membranes, strictly controlled inter-layer distance of graphene-based laminates and strong adhesion of graphene-based selective layers onto a porous polymer substrate are required to provide high salt rejection properties and desirable mechanical durability with chlorine tolerance in membrane processes. However, there is a difficulty in stabilizing graphene nanosheets as a membrane selective layer for the desalination process and controlling their interlayer distance. In this work, we demonstrate the successful fabrication of a graphene-based thin-film composite membrane by integrating graphene oxide (GO) nanosheets into a highly crosslinked polymer network on a porous polymer substrate. The resulting poly(N-isopropylacrylamide-co-N,N′-methylene-bisacrylamide) entwined GO thin-film composite membrane has a main GO interlayer spacing of 0.48 nm and a GO-polymer thin film of less than 40 nm thick and shows excellent water flux (25.8 L m^-1 h^-1) and salt rejection (a NaCl rejection of 99.9%), alongside excellent mechanical stability and chlorine tolerance for the forward osmosis process. This polymer network entwined GO thin-film composite can be effectively tailored as a platform material for developing high-performance osmosis desalination membranes for industrial application.