Surface-modified reverse osmosis membranes applying a copolymer film to reduce adhesion of bacteria as a strategy for biofouling control

Abstract

The hydrophilic hydroxyethyl methacrylate (HEMA) and the hydrophobic perfluoro decylacrylate (PFDA) were copolymerized and deposited on different substrates using an initiated chemical vapor deposition (iCVD) technique. By adjusting the relative flow rates of the two monomer gases, it was possible to control both the chemistry and thickness of the deposited films. Copolymers of different chemistries were first deposited on quartz crystals and the adsorption of a model polysaccharide, sodium alginate, was studied with the help of Quartz Crystal Microscopy (QCM). The copolymer film with amphiphilic chemistry showed considerably less foulant adsorption in comparison with the pure homopolymers i.e. PHEMA and PPFDA. The films were then deposited on commercial RO membranes and the modified surfaces characterized with AFM, CA and XPS. Resistance to bacterial adhesion was examined for the coated membranes by carrying out short-term batch studies with Escherichia coli cells. Among the different film chemistries, the membrane with the copolymer film of amphiphilic chemistry (∼40% PFA) showed the least microbial attachment. Bacterial adhesion tests were then repeated with the unmodified RO membrane and the membrane coated with the optimum chemistry. A quantitative analysis revealed that the presence of the amphiphilic copolymer film on the membrane results in a reduction of attached bacteria by about two orders of magnitude. To summarize, the surface modification of membranes with an initiated CVD technique presents a potentially effective strategy for the control of membrane biofouling.