ZnO@PMMA incorporated PSf substrate for improving thin-film composite membrane performance in forward osmosis process

The performance of the existing forward osmosis membranes is mainly restricted by the internal concentration polarization (ICP) of solutes inside the substrate. In the current work, the poly (methyl methacrylate) (PMMA) grafted ZnO nanoparticle (ZnO@PMMA) was synthesized and introduced as a novel nanofiller to minimize the ICP effect within the polysulfone (PSf) support layer. It was revealed that the ZnO@PMMA nanoparticles could improve the characteristics of the PSf membrane substrate, including the porosity, hydrophilicity, pure water permeability (PWP) and morphology. The optimal support layer has a porosity of 82.4% and PWP of 186.5. The FO performance of modified membranes in terms of water flux (Jw, LMH) and reverse salt flux (Js, gMH) were thoroughly evaluated using a cross-flow system. Also, the water permeability (A, LMH.bar−1) and salt rejection (R, %) were measured by a dead-end RO setup. The obtained TFN-ZP.2 membrane (modified with 0.25 wt% of ZnO@PMMA) showed significantly improved FO water flux (up to 14.6 LMH) and water permeability (2.3 LMH/bar) which was about 2 times that of the bare TFC-FO membrane (5.9 LMH and 1.2 LMH/bar). Additionally, the structure parameter (S) was significantly alleviated (693 ± 85 µm) after the ZnO@PMMA incorporating, indicating reducing the unwanted ICP in TFN-FO membranes.