Abstract
Biofilm is a significant cause for membrane fouling. Antibacterial-coated surfaces can inhibit biofilm formation by killing bacteria. In this study, polyethersulfone (PES) microfiltration membrane was photografted by four antibiotic quaternary ammonium compounds (QACs) separately, which were synthesized from dimethylaminoethyl methacrylate (DMAEMA) by quaternization with butyl bromide (BB), octyl bromide (OB), dodecyl bromide (DB), or hexadecyl bromide (HB). XPS, ATR-FTIR, and SEM were used to confirm the surfaces’ composition and morphology. After modification, the pores on PES-g-DMAEMA-BB and PES-g-DMAEMA-OB were blocked, while PES-g-DMAEMA-DB and PES-g-DMAEMA-HB were retained. We supposed that DMAEMA-BB and DMAEMA-OB aggregated on the membrane surface due to the activities of intermolecular or intramolecular hydrogen bonds. Bacteria testing found the antibacterial activities of the membranes increased with the length of the substituted alkyl chain. Correspondingly, little bacteria were observed on PES-g-DMAEMA-DB and PES-g-DMAEMA-HB by SEM. The antifouling properties were investigated by filtration of a solution of Escherichia coli. Compared with the initial membrane, PES-g-DMAEMA-DB and PES-g-DMAEMA-HB showed excellent anti-biofouling performance with higher relative flux recovery (RFR) of 88.3% and 92.7%, respectively. Thus, surface functionalization of the PES membrane with QACs can prevent bacteria adhesion and improve the anti-biofouling activity by the contact-active antibacterial property.
Highlights
Membrane separation technology which works without the addition of chemicals and with a relatively low energy cost has a great potential value in water purification [1,2,3]
Four quaternary ammonium compounds (QACs) with different lengths of alkyl chains were synthesized from dimethylaminoethyl methacrylate (DMAEMA) and grafted on PES membranes via UV
Pores on the membranes surfaces, which were grafted with short alkyl chain-substituted QACs, were narrowed and even blocked, because the hydrogen bonds might be created inter- or intramolecularly and monomers or polymers would assembled on the surfaces
Summary
Membrane separation technology which works without the addition of chemicals and with a relatively low energy cost has a great potential value in water purification [1,2,3]. The dispersion and dissolution may result in loss of effectiveness, and potential toxicological impacts restrict the application of AgNPs. Contact-active antibacterial material (CAAM) is protected by covalent linkage of an antibacterial agent to a surface [20,21]. Polymers with short alkyl chain exhibited greater antibacterial activities than their precursory monomers, but the contrary result was present in the long ones. They supposed this was due to the low solubility of the polymers with long alkyl chain in water restraining the penetration to the cell wall. Four quaternary ammonium salts (Figure 1) were synthesized from DMAEMA and grafted on PES membranes by a UV photointiation method.
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