Preparation And Application Of High Performance MWCNTS-OH / PVDF Hybrid Hollow Fiber Ultrafiltration Membrane

Polyvinylidene fluoride (PVDF) hollow fiber ultrafiltration membranes were prepared by the nonsolvent induced phase inversion process. Studying the effects of solvents, polymer concentration, surfactants and other factors on the structure and the performance of the membrane to determine the optimal formula and the optimal spinning conditions. Taken together, polymer concentration is 22wt%, LiCl concentration is 1.5wt%.With hydroxyl multi-walled carbon nanotubes(MWCNTs-OH) as carbonous fillers. The high-flux PVDF hollow fiber ultrafiltration membranes modified by MWCNTs-OH were prepared by the nonsolvent induced phase inversion process. Adding MWCNTs-OH into N,N-dimethyl acetamide (DMAC) solvent in ultrasonic processing in order to strengthen its dispersion, and strive to produce uniform casting membrane solution.The morphology and performances of composite membrane were characterized by scanning electron microscope(SEM),Fourier transform infrared spectroscopy(FTIR),X-ray diffraction(XRD),dynamic contact angle(DCA) and mechanical properties test.The effects of MWCNTs-OH on the water flux and rejection as well as mechanical properties of the resulted hollow fiber membrane were emphasized to investigate. The results showed that the water flux increased from 376.4L/m2h to 510.9L/m2h, while the rejection stabilized around 95.0% as the MWCNTs-OH loading increased from 0 to 0.09wt%. Tensile strength and stretching strain at break increased from 1.68 to 2.42MPa and 44.18% to 79.18%, respectively. The images of SEM and TEM indicates that MWCNTs-OH easy to reunite in the matrix along with the contents of MWCNTs over 0.09wt%, resulting in the decrease of the membrane tensile strength and water flux. The crystal form of the hollow fiber membranes changed little with the addition of MWCNTs-OH via the analysis of Fourier transform infrared (FTIR) spectroscopy and XRD.Studying the application of ultrafiltration and nanofiltration integrated process in the separation and purification and enrichment of ginkgo biloba flavonoids ingredients. PVDF ultrafiltration membrane remove other impurities in the feed liquid and nanofiltration membrane enriches active ingredients. The extract of ginkgo biloba flavonoids content increased 0.111g/L to 0.258g/L under the condition of 25℃ and 0.1 MPa. Compared with the production methods of macroporous resin adsorption, this separation method save operation time and improve operation efficiency and can effectively improve the concentration of flavonoids.