Surface modification of reverse osmosis membranes with zwitterionic coatings: A potential strategy for control of biofouling

In this article we report enhanced antifouling properties of reverse osmosis (RO) membranes surface-modified with zwitterionic copolymer films of poly(4-vinylpyridine-co-ethylene glycol diacrylate) (p(4-VP-co-EGDA)). The copolymer films were deposited onto the surface of RO membranes via an initiated chemical vapor deposition technique (iCVD) followed by a quaternization reaction with 3-bromopropionic acid. XPS analysis revealed that zwitterionic moieties were highly surface-enriched; concentrated in the top similar to 5 nm of deposited films. Resistance to fouling of the zwitterionic coatings was investigated by determining the extent of biopolymer adsorption via quartz crystal microbalance with dissipation monitoring. The surface-modified quartz sensors exhibited superior resistance to the adsorption of two biopolymers; bovine serum albumin (BSA) and humic acid (HA). Biofouling propensity of the modified RO membranes was further investigated using two bacterial strains abundantly present in seawater. The results showed similar to 98% lower attachment of both Pseudomonas aeruginosa and Bacillus licheniformis bacteria onto the surface of modified membranes as compared to virgin membranes. Molecular force mapping (MFP) was employed to investigate and quantify interaction forces between model foulant BSA and both bare and modified RO membrane surfaces. The results of MFP revealed that the adhesive force between the foulant (BSA) and membrane surface was at least an order of magnitude lower for the modified membranes when compared to virgin membranes. (C) 2015 Elsevier B.V. All rights reserved.