Graphene-based ultrafast nanofiltration membrane under cross-flow operation: Effect of high-flux and filtered solute on membrane performance

Two-dimensional materials-based membranes continue attracting research interest due to the ultrafast permeance and effective molecular sieving. However, measuring the nanofiltration performance of an ultrafast membrane under long-term filtration remains elusive, particularly when considering the effects of concentration polarization and cake formation on the flux decline and rejection rate. To address this question, we designed an ultrafast graphene oxide (GO) membrane using small-flake graphene oxide (SFGO) on the lateral scale of ∼100 nm, which was prepared using sonication. The SFGO membrane exhibited ultrafast permeance of 720–5410 L m⁻² h⁻¹ bar⁻¹ for several solvents (i.e., acetone, methanol, water, ethanol, and isopropyl alcohol), which could be attributed to the reduced diffusion length and increased effective membrane surface area. It was observed a drastic flux and rejection rate decline in both water and isopropyl alcohol in the filtration of several dye solutions using dead-end and cross-flow systems. This could be attributed to the concentration polarization and cake formation that occurred during the rapid accumulation of solute on the membrane surface due to the ultrafast solvent permeance.