Study On Preparation And Performance Of Smart Switchable Wettability Nanofiltration Membrane

Nanofiltration because of highly selective process, simple operation and low power consumption has been widely used in various industrial and scientific research. Nanofiltration process is divided into an aqueous solvent system and an organic solvent system. At present, nanofiltration is mainly in process for water solvent system, but the actual industrial processes also relates to the organic solvent system. Existing research to prepare for the water solvent system and organic solvent system are carried out using different methods. How to make the same kind of film not only may achieve its water solvent systems nanofiltration, but also can realize organic solvent nanofiltration system remains a challenge.In this paper, PSS-TiO₂/PEI polyelectrolyte complex nanofiltration is prepared by LbL technology on norganic ceramic tubular base film, alternating cationic polyelectrolyte polyethyleneimine?PEI? and polystyrene sulfonate anionic polyelectrolyte?PSS?, then use our group pre-prepared PSS-TiO₂ as the nanoparticles deposited, continuing to alternate deposition of cationic polyelectrolyte polyethyleneimine?PEI? and dispersed PSS-TiO₂ nanoparticles anionic polyelectrolyte sodium polystyrene sulfonate?PSS?. The PSS-TiO₂/PEI polyelectrolyte complex nanofiltration were characterized by SEM and contact angle. The results showed that PEI and PSS polyelectrolyte and PSS-TiO₂ nanoparticles in the membrane surface successfully conducted self-assembly alternately; And continue to ultraviolet light modification of membrane surface, it can obtain super hydrophilic surface, the membrane surface contact angle is 1.6 °. The membrane has the good separation effect being used to dye removal of water solvent system. When PEI and PSS polyelectrolyte concentration of 6mg/m L, PSS-TiO₂ dispersed in PSS concentration of 0.03g/L, assembled layers 4.5 layer, UV irradiation time was 80 min modified, Its retention rate was 95.23%, flux 269.23L/?m².h.MPa? for chrome black T dye, and retention rate of 100%, the flux of 161.54 L/?m².h.MPa? for dimethyl phenol orange dye.On this basis, the choice of having quaternary ammonium groups can be hydrophilic and hydrophobic modified poly diallyl dimethyl ammonium chloride?PDDA? a cationic polyelectrolyte, polyelectrolyte polystyrene sulfonate?PSS? as an anion polyelectrolyte, as well as PDDA-TiO₂ nanoparticles, polyacrylonitrile?PAN? ultrafiltration membrane as the base, hydrophilic-hydrophobic conversion PDDA-TiO₂/PSS polyelectrolyte complex membrane is prepared by Lb L and counter ion-exchange. The prepared hydrophilic-hydrophobic conversion PDDA-TiO₂/PSS polyelectrolyte composite nanofiltration membrane is characterized by contact angle, Zeta potential, SEM, AFM, ATR-FTIR and other characterizations. It proved that PDDA and PSS polyelectrolyte and PDDA-TiO₂ nanoparticles successfully assembled on the base film surface, the contact angle is illustrated by the characterization of ion exchange water to achieve t hydrophilic-hydrophobic conversion. The hydrophilic PDDA-TiO₂/PSS polyelectrolyte complex dye aqueous solvent nanofiltration membrane system for removal nanofiltration process, the hydrophobic PDDA-TiO₂/ PSS polyelectrolyte complex nanofiltration for Dye non-aqueous organic solvent system off, they have a good separation. When PDDA and PSS polyelectrolyte concentration of 5mg/mL, PDDA-TiO₂ dispersed in PDDA a concentration of 0.15mg/m L, assembling the layers to four layers, chlorine ion exchange counter, its rejection of the chrome black T dye solution system is 95.7%, and flux is 232.7 L/?m²·h·MPa?; when PDDA and PSS polyelectrolyte concentration of 5mg/m L, PDDA-TiO₂ dispersed in PDDA concentration of 0.15mg/mL, assembled layers 4.5 layer, perfluorooctanoic acid ion exchange counter, its rejection rate is 97.35% ethanol, and flux is105.32 L/?m²·h·MPa? for methylene blue organic solution system.