Effect of oxygen plasma treatment on the nanofiltration performance of reduced graphene oxide/cellulose nanofiber composite membranes

Graphene based nanosheets have been widely used as building blocks for fabrication of superior separation membrane for water processing. In particular, membranes made of reduced graphene oxide (rGO) show better stability compared with graphene oxide (GO). However, densely stacked of rGO often results in low water flux. In this study, cellulose nanofibers (CNFs) were incorporated into the rGO laminates by vacuum filtration of dilute GO/CNF solution and thermal reduction at 150 °C for 1.5 h. The resulting rGO/CNF membrane was treated with oxygen plasma for 1–4 min to create nanopores on the membrane surface for the purpose of enhancing nanofiltration performance. The results showed that the optimum membrane performance was obtained by using the equal amount of GO (31.83 mg m^-2) and CNFs accompanied by 3 min of plasma treatment, exhibiting a pure water permeance of 37.2 ± 3.9 L m^-2 h^-1 bar^-1 maintaining a rejection above 90% for Acid Fuchsin (1.2×1.1 nm), Rose Bengal (1.5×1.2 nm) and Brilliant Blue (2.2×1.7 nm).