Research On Comprehensive Performance Improvement Method Of PVC Ultrafiltration Membrane Based On Cationization Modification

Ultrafiltration has been used in water treatment because of its simplicity and efficiency,quality and cheap polyvinyl chloride(PVC)ultrafiltration membrane is also more and more people's attention.In water treatment,high water flux and rejection of membrane is the most sought-after goals.However,further improvement of ultrafiltration membrane performance was always limited by the "trade-off" effect.The problems of membrane fouling,especially biological fouling,also posed challenges to the antibacterial ability of ultrafiltration membranes.In order to break the "trade-off" effect,and enhance the antibacterial ability of the membrane at the same time,the in-situ quaternary modification of commodity PVC ultrafiltration membrane was carried out by soaking in trimethylamine(TMA)solution,which is based on the reactivity of C-Cl bond in PVC.In the experiment,the modification process was regulated by adjusting the concentration of TMA,the reaction time and the reaction temperature.Infrared spectrum(ATR-FTIR),X-ray photoelectron spectroscopy(XPS),1H nuclear magnetic spectrum(1H NMR)and Thermogravimetric(TG)analysis showed that the quaternary ammonium groups were successfully grafted onto the surface of PVC membrane.Surface Zeta potential analysis shows that the cationic layer is constructed on the surface of the modified membrane,which makes the membrane surface positively charged.The performance characterization of the modified membranes showed that the hydrophilicity of the membrane was enhanced,the pore size was reduced,the pure water flux and the rejection of carbon ink were increased,the antimicrobial activity was enhanced,and these change was affected by the modification conditions.Under the conditions of TMA concentration of 4.2 mol·L-1,reaction time of 4 h and reaction temperature of 45?,the pure water flux of the modified membrane was 432.2 L·m'-2·h-1,which was increased by 26%,the rejection of carbon ink was increased from 93.7%to 99.7%,the antibacterial rate of Escherichia coli was 60%,this achieved a simultaneous permeability,selectivity and antibacterial property improvement of PVC ultrafiltration membranes.In addition,the modification did not significantly reduce the mechanical properties of the membrane.After the comparison,the separation performance of quaternizated PVC membrane has surpassed the existing commercial ultrafiltration membrane.