Low internal concentration polarization in forward osmosis membranes with hydrophilic crosslinked PVA nanofibers as porous support layer

• Successful polymerization of polyamide on the surface of crosslinked PVA nanofiber substrate
• A low, tortuous and very hydrophilic support layer was successfully fabricated.
• Water permeability, A, of NC-PVA/PA membrane is 2.4 times higher than HTI-NW membrane.
• FO flux of NC-PVA/PA membrane is 7.5 times higher than HTI-NW membrane.
• NC-PVA/PA membrane exhibited the lowest S value, 66 ± 7.9 μm, in open literature.

Recent developments on osmotically driven membrane processes (ODMPs), e.g. forward osmosis (FO) and pressure retarded osmosis (PRO), suggest a high viability for clean water and energy production. However, membranes used in these processes encounter high internal concentration polarization (ICP), inherent to osmotically driven membranes, which keeps them from delivering optimum performance in terms of water flux. In this study, a nanofiber thin film composite (NTFC) membrane was synthesized. Crosslinked electrospun polyvinyl alcohol (PVA) nanofiber was uniquely found to be a very effective support layer, specifically for FO applications, due to its very low tortuosity, very high porosity and remarkable hydrophilic property. The successfully fabricated composite exhibited a 7–8 times improved FO water flux as compared to a commercially available FO membrane. Ultimately, our membrane displayed a lower structural parameter (S = 66 ± 7.9), a measure of ICP condition, compared to previously synthesized NTFC membranes. Based on the performance of our membrane, this hydrophilic nanofiber supported membrane, with further development, has the high potential to be the next-generation FO membrane.

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