In situ amphiphilic modification of thin film composite membrane for application in aqueous and organic solvents

Abstract

Conventional support (uncrosslinked) based polyamide (PA) thin film composite (TFC) membranes are indispensable for desalination and purification of water. In addition to water purification, an emerging application of TFC membrane is the nanofiltration of organic solvents if the support layer is solvent resistant. However, solvent resistant PA TFC membranes show good permeate flux of polar solvents but low flux of non-polar solvents. We report that amphiphilic PA barrier layer is required to obtain good permeate flux of polar and nonpolar solvents. Herein, a facile approach for the in situ amphiphilic modification of PA layer of TFC membrane for application in aqueous and organic (polar and non-polar) medium is reported. Amphiphilic PA layers have been fabricated on conventional polysulfone (PSf) and solvent resistant polyimide (PI) supports. Interfacial polymerization (IP) between mixture of m-phenylenediamine (MPD) and MPD-capped polyethylene glycol (MPD-PEG-MPD) and mixture of trimesoyl chloride (TMC) and TMC-capped polydimethylsiloxane (TMC-PDMS-TMC) produces amphiphilic TFC membranes. Hydrophobic TFC membranes have been prepared by the IP between MPD and mixture of TMC and TMC-PDMS-TMC. The TFC membranes exhibit tunable water wetting behavior (water contact angle = 61-110o) depending on the composition of the organic phase. Amphiphilic TFC membranes show surface rearrangement/reconstruction behavior in contact with water and non-polar solvent. The amphiphilic membranes show good antifouling property with reduction of flux to about 14% and recovery in the flux to about 97% during desalination of water containing bovine serum albumin. The hydrophobic and amphiphilic TFC membranes (solvent resistant) showed significant improvement in the permeate flux of toluene and hexane. Particularly, amphiphilic solvent resistant membranes are suitable for application in water and nanofiltration of polar and non-polar solvents.