Graphene oxide modified forward osmosis membranes with improved hydrophilicity and desalination performance

Graphene oxide (GO) was applied to fabricate thin-film nanocomposite forward osmosis (TFN-FO) membranes with improved desalination performance. GO in various concentrations ranging from 0.0005 to 0.06 wt% was added to the aqueous phase solution before the interfacial polymerization process. GO modified FO membranes were characterized and the desalination performance was investigated. Results indicated that the TFN-FO membranes formed a typical "ridge-and-valley" structure, achieved a lower reverse solute flux, and showed improvements on membrane hydrophilicity, water fluxes, and salt rejection. When 2 mol.L-1 of NaCl and 10 mmol.L-1 NaCl were used as the draw solution and the feed solution, respectively, the water flux of the membrane modified by 0.005 wt% GO reached the climax at 8.59 L.m(-2).h(-1) (LMH) in the active layer facing the feed solution mode (the active layer facing the draw solution), which increased 55.6% compared with that of the pristine membranes. Moreover, the desalination performance of TFN-FO was compared with the pristine FO membranes under different operating conditions with various draw solution concentrations, cross-flow rates and orientations of membranes. Results showed that the TFN-FO membranes had enhanced desalination performance under all operating conditions in this study. The 0.005 wt% GO nanosheet was the optimal and such low contents of GO are promising for a wide-scale industrial application.