Thin-film composite (TFC) membranes with hydrophilic ethyl cellulose-graft-poly(ethylene glycol) (EC-g-PEG) substrates for forward osmosis (FO) application

Abstract

In this work, ethyl cellulose-graft-poly(ethylene glycol) (EC-g-PEG) was synthesized by esterification of carboxylic acid functionalized methoxy polyethylene glycol (MPEG-COOH) with ethyl cellulose (EC) in order to develop the substrates of thin-film composite (TFC) membranes for forward osmosis (FO) application. The TFC membrane consists of a selective polyamide active layer formed by interfacial polymerization on top of EC-g-PEG substrate fabricated by phase separation. The EC-g-PEG substrates were characterized by water contact angle, porosity, surface roughness, and morphology. It was found that hydrophilicity and porosity of the EC-g-PEG substrate were increased as compared with those of the EC substrate. Using a 2 M NaCl as draw solution and DI water as feed solution, the TFC membranes of EC-g-PEG (TFC-EP) exhibited a 15.7 LMH of FO water flux, while TFC membranes of EC exhibited only 6.6 LMH of FO water flux. Enhanced FO performances of TFC-EP membrane are attributed to increased hydrophilicity and porosity, which play a crucial role in water flux. Moreover, the increase in water permeability and porosity of TFC-EP can be attributed to decrease in structural parameter which resulted in decreased internal concentration polarization (ICP) in EC-g-PEG substrates.