Preparation And Characterization Of Modified PVDF Hollow Fiber Membrane With The Regenerative Fluorine Sulfonic Acid (PFSA) And Hydroxyapatite (HAP)Whisker

This thesis sdudied that preparation and characterization of modified PVDF hollow fiber membrane using the regenerative fluorine sulfonic acid (PFSA) and hydroxyapatite whisker (HAP).The regenerative PFSA was modified PVDF membrane. Then it investigated that the influence of property of PVDF hollow fiber membrane and mechanism of formation PVDF flat film in precipitation process. Secondly, the HAP whisker was self-synthesized by homogeneous precipitation method in laboratory using to modify PVDF membrane. Then discussed that the performace of PVDF membrane were influenced by the HAP nano whisker(1) The roles of alkali metal counter-ions (Li, Na, K and Rb) of PFSA play in the formation of polyvinylidenefluoride (PVDF)/PFSA-M hollow fiber membranes were detailed investigated. Experimental results prove that the counter-ions of PFSA play important roles in the formation of PVDF/PFSA-M hollow fiber membranes. With the counter-ion of PFSA varying from Li, Na and K, the homogeneous region in the ternary phase diagram of the PVDF-PFSA-M/NMP/H2O systems shrinks and the precipitation rate in water increases. The double finger-like structure and the cavities evidently develop with the increase of the radius of the counter-ions of the spun PVDF/PFSA-M membranes. The pure water permeability (Jw) and mean effective pore size of the PVDF/PFSA-M membranes firstly increase from counter-ion Li, Na to K and then decrease a bit for Rb. The highest Jw value96.5L·M-2·H-1·Bar-1were obtained for the PVDF/PFSA-K membrane with a MWCO of86kDa.(2) A series of PVDF-PFSA ultrafiltration membranes was prepared by wet phase-inversion method and vacuum evaporation technology. Then analyses mechanism of formation PVDF-PFSA membrane by SEM、FTIR-ATR、contact angle、membranes potential and XPS test method and so on. From the SEM seen that the PFSA-PVDF blend has two different structure by wet phase-inversion method, the upper surface and finger-like support layer. However, the upper surface and cross-section of PVDF-PFSA membrane are all dense structure prepared by vacuum evaporation method. With the mass of PFSA increasing, the hydrophilic of PVDF-PFSA fleet film develops obviously, the pure permeation flux (PWP) increases from22.37L·M-2·H-1to976.65L·M-2·H-l,the rejection for BSA protein first decreases then increases. FTIR-ATR spectra shows that the-SO3-inside blend membrane which were prepared by phase-inversion method appears more membrane surface and porous surface, but distributes homogeneous inside composite membrane by vacuum evaporation method prepared. Furthermore,the results of streaming potential and XPS test also indicates that the potential(ε) of surface membrane decreases gradually, the membrane of Hydrophilic groups--SO3-exsits more the membrane surface and porous surface as the increase of PFSA mass fraction in phase-inversion process.(3) A novel organic-inorganic composite membrane, polyvinylidenefluoride (PVDF)-hydroxyapatite (HAP) hollow fiber composite membrane were fabricated by wet spinning method. The spun PVDF-HAP hollow fiber composite membranes were well characterized by numerous state-of-the-art analytical techniques:SEM, AFM, XRD, DSC, FTIR-ATR and mechanical test and elucidated accompanying with its precipitation kinetics obtained by light transmittance measurements. The precipitation process results confirm that PVDF/HAP/NMP dopes experience delayed demixing mechanism and the precipitation rate slightly increases as the HAP content increases. The SEM images indicate that the distinct three-layer structure, a sponge-like layer sandwiched by two finger-like layers, exist in the cross sectional morphologies of the composite membranes. The melting temperature (Tm) of the PVDF-HAP hollow fiber composite membranes increases with the addition of HAP whiskers. IR spectra and XRD patterns verify the exclusively formation of β crystalline phase structure in the as-spun PVDF-HAP composite membranes. Mechanical properties of the as-spun PVDF-HAP composite membranes evidently increased. The Young’s modulus of PVDF-HAP hollow fiber membrane increases from66.8Mpa to129.9Mpa as the nano HAP whisker content increases from0%to3%. The tensile strength of the PVDF-HAP composite membranes also is evidently improved from2.54Mpa to3.81-4.31Mpa by adding HAP whiskers from1%to3%. The elongation ratio of the PVDF-HAP composite is also improved, which is different from the polymeric membranes modified by other inorganic nano particles. The permeation flux of the PVDF-HAP hollow fiber membranes slightly increases with the increase of the HAP content in the composite membranes since its hydrophilicity is improved.(4) The main purpose is improved the pure permeation flux(PWP) of PVDF-HAP hollow fiber membrane which adding the PVP as additives on the basis of fourth chapter. Research showed that adding a certain amount of PVP can improve the PWP of PVDF-HAP hollow fiber membrane evidently. With the HAP whisker adding, the PWP of PVP/PVDF-HAP hollow fiber membrane first increases to311.2L. M-2. H-1, then decreases to118.5L.M-2. H-1,the rejection for BSA protein also decreases to a lowest point of33.3%then increases as the mass fraction of HAP increasing,...