Hydrophilic and antibacterial properties of polyvinyl alcohol/4-vinylpyridine graft polymer modified polypropylene non-woven fabric membranes

Membrane filtration processes in water treatment have increased considerably in the past decades. However, the disadvantages of common hydrophobic membrane materials are that they cause serious bio-fouling and decrease of permeate fluxes. In this work, a novel polyvinyl alcohol/4-vinylpyridine graft polymer (PVA-g-4VP) was prepared and adsorbed on polypropylene non-woven fabric (NWF) membrane surface and pore walls to improve both hydrophilic and antibacterial properties of the membrane. Fourier transform infrared spectroscopy and elemental analysis were employed to confirm the graft reaction. X-ray photoelectron spectroscopy and environmental scanning electron microscopy were employed to confirm the modification on the membranes. Water contact angle was measured to evaluate the hydrophilicity. The water contact angles for the membranes decreased from 123 ± 1.2° to 33.4 ± 2.5° with increasing PVA-g-4VP concentration from 0 to 1.5 wt.% in the adsorption solution during modification. Flux and rejection of the modified membrane in supernatant solution of active sludge were measured. The modified membranes had lower water permeate fluxes, higher rejection rates and better antifouling property than those of the original NWF membrane. Live/dead cell staining results of the attached bacteria on the membranes also revealed that a more antibacterial surface can be obtained by quaternizing PVA-g-4VP modified membrane surface with benzyl bromide.