Submitted to: Journal of Adhesion Science and Technology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/2/2010
Publication Date: 1/2/2011
Citation: Liu, S.X., Kim, J. 2011. Characterization of surface modification of polyethersulfone membrane. Journal of Adhesion Science and Technology. 25:193-212. Interpretive Summary: We successfully demonstrated that membrane surface modification with water compatible, hydrophilic polymer would reduce protein adsorption in various degrees thus cutting down the downtimes of membrane process operations and reducing production costs of food protein processing. In this study, we compared two methods of surface modification of membrane material used in food protein concentration and fractionation: UV/ozone-treated grafting and interfacial polymerization. Several hydrophilic polymers were attached to the membrane surface to improve surface hydrophilic in order to reduce the membrane fouling, a common costly problem in membrane processes. Hydrophilic polymers, poly(vinyl alcohol) (PVA), polyethylene glycol (PEG), and chitosan were used to form a hydrophilic layer on top of the PES membrane. Modified PES membranes were tested by various analytical instruments. The results of these instrumental analyses indicated that the modified PES membranes are more hydrophilic. We found that UV/ozone-treated grafting method produced more significant adsorption reduction than interfacial polymerization method does. This research result can be used by food processors and membrane modules manufacturers to improve the membrane process efficiency in the manufacturing of foods containing proteins.
Technical Abstract: Surface modification of polyethersulfone (PES) membrane surface using UV/ozone-treated grafting and interfacial polymerization on membrane surface was investigated in order to improve the resistance of membrane surface to protein adsorption. These methods of surface modification were compared in terms of hydrophilicity, chemical composition of the surface, and static protein adsorption. In both methods, poly(vinyl alcohol) (PVA), polyethylene glycol (PEG), and chitosan were chosen as hydrophilic polymers to chemically modify the commercial virgin PES membrane more hydrophilic as these materials have excellent hydrophilic property. Modified PES membranes were characterized by contact angle and XPS. Contact angles of modified PES membranes were reduced by 19% to 58% of that of the virgin PES membrane. PES membrane modified with PEG show higher wettability than other hydrophilic materials with the highest contact angle reduction shown in UV/zone treated, PEG grafted PES membrane surface. In general, XPS spectra supported that the PES membranes were successfully modified by both UV/ozone grafting and interfacial polymerization methods. The results of the static protein adsorption experiment show all surface modifications led to reduction in protein adsorption on PES membranes; the highest protein adsorption reduction occurred with membrane modified by UV/ozone treatment followed by PES grafting, which corresponded to the highest contact angle reduction. However, there seems no clear correlation between contact angle reduction and reduction in protein adsorption in situation that involved chitosan. Nevertheless, membranes modified with chitosan do show higher reduction in protein adsorption than membranes modified with other materials under the same conditions.