Research On The Modification Of PVDF Membrane Based On Supramolecular Chemistry Process And Its Application In The Treatment Of Lower Concentration Oily Wastewater

In this dissertation, a research has been made on the surface hydrophilic modification of porous polyvinylidene fluoride(PVDF) membrane based on supramolecular chemistry process and its application in the treatment of low concentration oily wastewater.First, the mechanism of surface hydrophilic modification of PVDF membrane based on supramolecular chemistry process has been presented. Supramolecular chemistry is the chemistry of ordered arrays of molecular units based on non-covalent weak interactions; it mainly studies the structure and function of the molecular assembly which are formed through the non-covalent bond weak interaction between two or among more molecules, such as hydrogen bond, van der waals force, dipole/dipole interaction, hydrophilic/hydrophobic interaction and their synergistic reaction. As a branch of supramolecular chemistry, the construction and function of the layer assembly of ultrathin membrane has been the hot issue to be studied. There are many kinds of impetuses to prepare ultrathin film by alternant sediment technique, such as electrostatic force, hydrogen bond, coordination bond, charge transfer, van der waals force, π-π interaction, molecular recognition or the synergistic reaction of several forces above. Though those all are weak interaction forces and the intensity is not strong, the total force is strong enough to preserve the stability of assembly system if these weak interactions are accumulated.Taking the water contact angel and pure water flux as the performance indexes, the main influence factors on performance of modified membrane are researched, and the main experimental conditions of membrane modification are determined. After modification, the water contact angle is 35° and pure water flux are over 100Lm^-2h^-1, which are improved greatly compared to the PVDF membrane, and the oil rejection ratio is increased dramatically. Moreover, the thermal stability and the mechanical stability of modified membrane is slightly increased.In order to ensure the stability of surface layer, the partial cross-linking reaction happened between glutaraldehyde and PVA which was on PVDF membrane by hydrogen bond, which not only insure the hydrophilicity of PVDF membrane, but also improve the stability of modified membrane.Taking advantage of Fourier transform infrared spectrum and X-ray photoelectron spectroscopy, the researcher has conducted a contrastive research on the surface molecular structure of porous PVDF membrane before and after modification. Research results indicate that, though the C-F characteristic peak of the PVDF membrane still exists after...