Effects of polyethylene glycol and its block copolymer on the property and performance of the thin film composite

Polyethylene glycol (PEG) and amphiphilic PEG-block-polysulfone-block-PEG (PEG-b-PSU-b-PEG) triblock copolymer were prepared to modify the substrate of the thin film composite (TFC) membrane. The effects on the physical and chemical properties, structure, and separation performances of the membrane were investigated. The PEG-b-PSU-b-PEG modified substrate was not conducive to the formation of the high-quality active layer by interfacial polymerization (IP), although the substrate hydrophilicity was improved. The forward osmosis (FO) performances of the membrane were worse than those of the unmodified membrane. In contrast, the PEG modified membrane exhibited superior performances. The water flux (Jw) was 22.29 LMH using 1 M NaCl draw solution (DS), corresponding to a notable increase of 23.3% than that of the unmodified membrane. The specific reverse salt flux (Js/Jw) was as low as ~ 0.1 g/L. The direct incorporation of PEG was a more effective and simple strategy for the substrate modification, compared with PEG-b-PSU-b-PEG. For the first time, this study reports the adverse effect of hydrophilicity on the TFC-FO membrane performance.