Preparation And Characterization Of Nano ZnO Entrapped In The Modified PVDF Ultrafiltration Membranes

Polyvinylidene fluoride (PVDF) ultrafiltration (UF) membrane has excellentchemical stability, outstanding capabilities resistant to high temperature, as well asgood mechanical properties. However, the application of PVDF membranes is stillrestricted due to the hydrophobic property of the membrane surface. When PVDFmembrane contacted with protein-containing solutions during filtration, an inevitablefouling of solute proteins took place on both sides of the membrane surface and thewall of the pores. Nano-ZnO particle has prominent catalytic activity. Thesupplementation of Nano-ZnO particles improved the hydrophilicity, mechanical andother properties of the PVDF membrane. Poly(methyl methacrylate)(PMMA) owneda high hydrophilicity, and it exhibits thermodynamic compatibility with PVDF over awide range of blend compositions, where this characteristic can be useful in thefabrication of a hydrophilic membrane. With blending the PMMA,ZnO-PMMA/PVDF blending UF membrane showed the excellent hydrophilicity,high anti-fouling property and good mechanical property.When the PVDF content increased from13wt.%to23wt.%, the pure waterfluxes decreased from4.2410-5m3·m-2·s-1to4.8610-6m3·m-2·s-1，BSA rejectionincreased from18.15%to76.27%. The porosity and the mean pore size ofmembranes decreased with the increment of PVDF content.The contact angle of PVDF microfiltration membranes decreased from82.33°to70.06°by the addition of Nano ZnO. When the addition of Nano ZnO content was0.005wt.%, the pure water flux (1.26×10-4m3·m-2·s-1) was found to be maximal andthe membrane showed the minimum total resistance (1.15×1013m-1) due to its highestporosity, largest pore size and the considerable improvement in hydrophilicity. Thetensile strength initially increased with the addition of Nano ZnO and reached amaximum value (2.92×106Pa) when the Nano ZnO content was0.01wt.%, and thendeclined as the Nano ZnO content was gradually increased.When the Nano ZnO content of dopes increased from0wt.%to1.5wt.%, thecontact angle of PVDF ultrafiltration membranes decreased from70.25°to63.21°.When the Nano ZnO content of dopes increased from0.001wt.%to1.5wt.%, the pure water flux increased from1.10×10-5m3·m-2·s-1to4.09×10-5m3·m-2·s-1, BSArejection increased from54.22%to96.38%. The tensile strength initially increasedwith the addition of Nano ZnO and a maximum value (2.16×106Pa) was achievedwhen the Nano ZnO content was0.1wt.%, and then declined as the Nano ZnOcontent was gradually increased.When the PMMA content of polymer increased from0wt.%to20wt.%, thecontact angle decreased from78.18°to61.24°, the surface tension increased from38.49mJ·m-2to43.07mJ·m-2. The ZnO-PMMA/PVDF blending UF membraneshowed a high pure water fluxes contrasting with the PMMA/PVDF membrane.When the PMMA content of polymer was5wt.%, the photo-catalytic self-cleaningratio achieved91.4%after5times of photocatalytic process.