Evaluating graphene oxide and holey graphene oxide membrane performance for water purification

Graphene oxide (GO) membranes have demonstrated desirable performance for purifying water, matching or exceeding the ion rejection and water flux properties of reverse osmosis (RO) membranes. Though previous methods (e.g., surface decoration and d-space tuning) have been investigated to improve GO membranes, thermal treatment can induce the formation of holes in GO nanosheets in a controlled manner. The resulting holey-GO (hGO) membranes are hypothesized to have improved water permeability via decreasing the path-length that water molecules must travel through the membrane; specifically, through cross-sheet junctions, which is currently one of the main bottlenecks in other GO membranes. GO and hGO membranes with varying thicknesses were fabricated on polycarbonate supports and evaluated with ion transport tests in a diffusion cell via permeate conductivity. Permeability tests were conducted using a dead-end filtration cell (0.27 MPa–0.48 MPa). Produced hGO membranes demonstrated up to 3.8 times higher permeability relative to GO membranes, despite being up to 4 times thicker. Additionally, the empirical upper bound for a modified Robeson plot measuring permeability and selectivity was exceeded by both GO and hGO membranes demonstrated in this work.