Facile and effective strategies are needed to modify forward osmosis (FO) membranes for improved resistance to organic fouling. Fouling resistant FO membranes will advance the commercial implementation of FO for treating feed waters with high fouling potential, such as wastewater and brines. We report a membrane modification technique for post-fabrication grafting of a poly(ethylene glycol) (PEG) block copolymer to the surface of commercial thin-film composite (TFC) FO membranes via an amide coupling reaction. The PEG concentration for membrane modification is optimized based on increased membrane hydrophilicity and reduced water permeability that result from increasing PEG concentrations during modification. Modified membranes exhibit improved resistance to organic fouling compared to unmodified control membranes when exposed to an aggressive synthetic wastewater mixture. The fouling resistance is achieved despite the non-uniform grafting of PEG, which is attributed to the limited accessibility of carboxylic group binding sites on the membrane surface. The fouling resistance of membranes modified using this post-fabrication technique compares favorably to TFC-FO membranes modified using other procedures. The modification technique we report in this work has the advantages of being relatively inexpensive, easy to implement, and applicable to commercial membranes.
Bibliographical noteFunding Information:
Financial support from the Department of Defense through the Strategic Environmental Research and Development Program (SERDP, Project ER-2217 ) is gratefully acknowledged. We also acknowledge a STAR Fellowship awarded by the US Environmental Protection Agency to D.L.S. is fellowship FP-91750001-0, a Graduate Research Fellowship awarded by the US National Science Foundation to H.J. is fellowship 2013162783, and a graduate fellowship awarded by the China Scholarship Council to X.L. Facilities use was supported by YINQE and NSF MRSEC DMR 1119826 . We thank Oasys Water, Inc. for providing the TFC-FO membrane samples.
- Forward osmosis
- Poly(ethylene glycol)
- Surface modification