Improved performance of thin-film composite forward osmosis membrane with click modified polysulfone substrate

In this study, polysulfone-graft-poly(2-dimethylaminoethyl methacrylate) (PSf-g-PDMA) as a pH-responsive graft copolymer was synthesized for the first time via a combination of click chemistry and atom transfer radical polymerization (ATRP). This graft copolymer was blended with polysulfone during the phase inversion. The so formed substrate was used for the fabrication of a forward osmosis (FO) membrane via interfacial polymerization. The influence of the copolymer concentration on hydrophilicity, morphology, porosity, FO performance, and TFC layer characteristics were thoroughly investigated using diverse analysis. To prove pH-sensitivity of the PSF-g-PDMA blended substrate, the pure water permeability (PWP) of substrate containing 10.0 wt% of PSf-g-PDMA copolymer (G₁₀) was measured at different pH values (3.0–12.0). As the pH of the feed solution was changed from 3.0 to 12.0, the PWP increased from 221.3 to 299.4 LMH/bar. In addition, the performance of PSF-g-PDMA based TFC membrane in FO process was studied. Compared to the pure PSf based TFC membrane, the PSf-g-PDMA modified TFC-FO membranes demonstrated increased water flux without adversely affecting their selectivity. In addition, the TFC-G₁₀ membrane exhibited a reversible pH-dependence water flux. The pH-reversibility was investigated using draw solution with different pH values (3.0 and 10.0) where acidic draw solutions show higher water fluxes than basic draw solutions.