Hydrophilic Antifouling Thin-Film Nanocomposite Forward Osmosis Membranes: Effect of Zwitterion-Functionalized Carbon Nanofiber Modification

The polyamide (PA) active layer plays a key role in the permeation and antifouling properties of thin-film composite (TFC) membranes. In this study, we synthesized a nature-based zwitterionic thin-film nanocomposite (TFN) membrane with improved organic fouling resistance. Hydrophilic zwitterionic poly-(sulfobetaine methacrylate) (PSBMA) was chemically introduced onto the surface of cellulose nanofibers (CNFs) to form CNF-g-PSBMA, which was subsequently incorporated into the PA selective layer. The cross-sectional transmission electron microscopy images and 3D atomic force microscopy surface topographies of synthesized TFC membranes showed that CNF-g-PSBMA led to the formation of a thinner and smoother PA layer. The performance of membranes was investigated in a forward osmosis (FO) filtration setup in two FO and pressure-retarded osmosis (PRO) modes. The water flux in FO and PRO modes showed an increase of 16.3 and 38 LMH, respectively, with a reverse salt flux similar to that of the pristine membrane. The modified TFN membranes revealed enhanced antifouling properties against sodium alginate and bovine serum albumin foulants up to four times compared with the unmodified TFC because of their improved hydrophilicity and smoother surface. The CNF-g-PSBMA-modified TFNs demonstrated great potential for use in FO filtration, thanks to the incorporation of nature-based green materials, which significantly enhanced the membrane performance.