Surface Properties and Reduced Biofouling of Graft-Copolymers That Possess Oppositely Charged Groups

Abstract

Microbial biofilms and their components present a major obstacle for ensuring the long-term effectiveness of membrane processes. Graft polymerization on membrane surfaces, in general, and grafting with oppositely charged monomers, have been shown to reduce biofouling significantly. In this study, surface forces and macromolecular properties of graft copolymers that possess oppositely charged groups were related to their potent antibiofouling behavior. Graft polymerization was performed using the negatively charged 3-sulphopropyl methacrylate (SPM) and positively charged [2-(methacryloyloxy)ethyl]-trimethylammonium (MOETMA) monomers to yield a copolymer layer on polyvinylidene fluoride (PVDF) surface. Quartz crystal microbalance with dissipation monitoring (QCM-D) technology was used to monitor the reduced adsorption of extracellular polymeric substances (EPS) extracted from a membrane bioreactor (MBR) wastewater treatment facility. Complemented measurements of attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy provided evaluation of the antifouling properties of the surface. Increase in water content in grafted layer exposed to 100 mM aqueous NaCl solution was observed by QCM-D. Therefore, the grafted copolymer layer is swelled in the presence of 100 mM NaCl because of reversing of polymer self-association by counterions. Force measurements by atomic force microscopy (AFM) showed an increased repulsion between a carboxylate-modified latex (CML) particle probe and a modified PVDF surface, especially in the presence of 100 mM NaCl. The hydration and swelling of the grafted polymer layer are shown to repel EPS and reduce their adsorption. Delineating the surface properties of antifouling grafted layers may lead to the design of novel antifouling surfaces.

Zwitterionic copolymer self-assembly for fouling resistant, high flux membranes with size-based small molecule selectivity

“…They have been shown to be highly resistant to biomolecular fouling due to their high degree of hydration [32][33][34][35][36][37]. Since this discovery, many researchers have improved the fouling resistance of membranes by attaching zwitterionic groups on their surface, by post-processing existing membranes [38][39][40][41][42][43][44] or by using zwitterionic surface-segregating additives [45][46][47].…”

Facile evaluation of coating thickness on membranes using ATR-FTIR

“…The surface of separation membranes plays an important role in their performance and propensity to fouling [1][2][3][4] and extra layers added on top of a membrane, purposely or unintentionally, can profoundly affect these characteristics. Surface modification of membrane using coating or grafting, fouling and biofouling phenomena are most common cases where such layers are encountered [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19].…”

Effect of sludge retention on UF membrane fouling: The significance of sludge crystallization and EPS increase

“…Firstly, modifying the membrane surface or structure with materials such as anti-adhesion and anti-bacteria compounds (Liu et al, 2010;Herzberg et al, 2011;Liu et al, 2012), or applying quorum quenching enzyme (acylase) and fungal inoculation on the membrane surface (Okamura et al, 2010;Kim et al, 2011) have proved to be effective ways to reduce the attachment between flocs and the membrane. Secondly, changing the properties of the flocs by adding anionic coagulant aids (Kim et al, 2012), polyelectrolytes (Dizge et al, 2011) and flocculants (Ji et al, 2010;Yu et al, 2013) have been studied, as well as the effect of flow residence times in the membrane tank (Kimura et al, 2009;Khan et al, 2013).…”