Low Temperature Plasma Modification Of PVDF Hollow Fiber Membrane And The Performance Study

With the progress of society and the development of science and technology，the waterresources has become one of the problems that cannot be ignored in the economicdevelopment in China, and the government focus on water issues more and more. In watertreatment，membrane technology is especially wide. Along with the rising standard of waterpurification and sewage treatment in China, membrane technology have transfered from theindustrial water treatment sector to water purification and municipal wastewater areas. Ascore parts of the membrane technology, film have a number of disadvantages in the real world,such as easily polluted, uneasily cleaning, high economic costs, operation cost andmaintenance cost and so on. In the subject, for the disadvantages of above of film, wemodified PVDF membranes hollow fiber membranes by low temperature plasma surfacemodification to improve membrane performance and anti-pollution ability.In the subject, we modified PVDF hollow-fiber membrane by four different types of lowtemperature plasma treatment. They are only plasma treatment, Hybrid plasma-chemicaldeposition, Plasma-liquid-phase grafting and Acrylic plasma chemical deposition. Wecompared Zeta potential of membrane surface and membrane pore, mechanical properties,infrared spectrum and surface morphology of modified and original film. We studied thedifference of pure water flux, flux in response to temperature, pH and salt of modified andoriginal film. Finally, in self-made attapulgite clay suspension liquid and MBR reactor, wecompared anti-pollution performance in the practical application. The conclusions are asfollows：(1) After modified by low temperature plasma treatment, the Zeta potential of membranesurface and membrane hole increase significantly. After treatment by Only plasma treatment,Hybrid plasma-chemical deposition, Plasma-liquid-phase grafting and Acrylic plasmachemical deposition, Zeta potential of film hole increased separately by234.65%，287.40%，201.18%and175.20%,and membrane surface is respectively1005.77%、1030.00%、1001.92%and340.38%.After modified, when the film is under tension, the ability to resistdamage is basically unchanged, but the plastic lowers, stiffness increases. Observing theelectron microscope picture of modification and original film, the original membrane surfaceis smoother, and membrane pore size distributed uniformity, looks clearly. And modifiedmembrane surface have a large bump up and down, and does not see the holes, can seeaggregate deposition in the local.(2) After modified by low temperature plasma treatment, the membrane flux increase by 2%~15%. The flux of modification and original film with the raise of temperature increases.The flux increase rate with temperature of modified membrane fluxes is lower than theoriginal film. As the temperature increases, the margin decrease. Responses of membranefluxes on pH value showed that, after modified by Acrylic plasma chemical deposition andHybrid plasma-chemical deposition, in acid and alkaline solutions, membranes have greaterflux response values. It say that after modified, both films have stronger acidic functionalgroups, and the later have greater degree of ionization. But after modified by Only plasmatreatment and Plasma-liquid-phase grafting, the response of membrane fluxes in acidconditions is stronger than alkaline conditions. The response of flux of PVDF plasma surfacemodification membrane is more complex to different electrolyte solutions and differentconcentrations. Main reasons are adsorption-osmosis cause membrane aperture reducing, andflux decline. Beside, electric shielding and neutralization of electrolyte ions to graftpolymerization of polymer chains cause membrane aperture increasing, and flux increase.And sticky induced by streaming potential causing counterion reverse migration.(3)In membrane separation processes, the larger change of membrane potential, thelower resistance of membrane fouling; modification of membrane flux decay rate is typicallylower than the original film, and the proportion of irreversible pollution of modificationmembrane is lower. Showed that the plasma-modified membranes, because of the highersurface Zeta potential and better hydrophilicity，the stain resistance properties improve.