Enhancing the Efficiency of a Forward Osmosis Membrane with a Polydopamine/Graphene Oxide Layer Prepared Via the Modified Molecular Layer-by-Layer Method

Water scarcity is one of the most critical problems that humans have to face. Working toward solving this problem, we have developed a thin-film composite (TFC) membrane using the modified molecular layer-by-layer (modified mLBL) method to fabricate polyamide (PA) active layers on different substrates. Besides, it has been found that graphene oxide (GO) contains abundant functional groups such as hydroxyl and epoxide groups, which are able to improve both the physical and chemical properties of the forward osmosis (FO) membrane. Thus, we have employed graphene oxide (GO) as the substrate and used the modified mLBL method to prepare active polydopamine/graphene oxide (PDA/GO) layers to enhance the water flux of the forward osmosis (FO) membrane. PDA/GO-coated layers could enhance the hydrophilic nature of the substrate and lower its surface roughness, which would facilitate the formation of the PA layer. Moreover, the PDA/GO coating can be applied to all substrates because of the high degree of adhesion of PDA to different substrates. In this study, the highly hydrophilic poly(vinylidene fluoride) membrane is superior in FO properties, with a water flux of 17.32 LMH and a reverse solute flux of 4.34 gMH. In addition, an excellent performance of 60.15 LMH and 14.88 gMH can be achieved when the pressure-retarded osmosis (PRO) test mode with a draw solution concentration of 2.0 M is used in the test. It shows that the membrane prepared using the novel method showed excellent FO performance, which has high potential in industrial applications such as desalination.