Study On The Structure And Properties Of Nano - Inorganic Particles Modified PVDF Membrane

Poly (vinylidene fluoride) (PVDF) membranes are broadly applied in many fields owing to their excellent chemical resistance, good thermal stability and mechanical properties. However when treating with wastewater, PVDF membranes are easily contaminated by pollutant, degrading their properties due to the hydrophobicity. It leads to declining flux and shorting lifespan of PVDF membranes, which further limits their large scale applications. Besides, the permeability of PVDF membranes prepared by wet-inversion (immersion precipitation) method is low. In order to enhance the integrative capabilities of PVDF membranes, TiO2 and MWCNTs were doped to PVDF to form PVDF composite membrane through Vapor-induced phase separation (VIPS) technique.The strategy of doping inorganic oxide particles to polymers to fabricate organic-inorganic composite membranes is particularly attractive owing to its simple preparation technology and obvious effect for enhancing membranes capabilities.Various techniques such as field emission scanning electron microscope (FESEM), pore size distribution, porosity, water flux, contact angle goniometry, static protein adsorption as well as tensile test were applied to characterize the effect of TiO2 and MWCNTs on the morphology, permeability, anti-fouling performance of the nanocomposite membranes. We also investigated the effect of temperature, humidity and the content of PVDF on the performance and morphology of composite membranes. The main experiment methods and results were summarized as follows:PVDF film-forming process will affect membrane structure and performance, through experiment results, when PVDF concentration is 25%, temperature is 50 ℃, humidity is 80wt%, the performance of the PVDF/TiO2 and PVDF/MWCNTs membranes were better. Through the test of PVDF/TiO2 membrane, the results showed that when TiO2 concentration was 1%, the water flue, hydrophilic, the amount of protein adsorbed to the surface, the pore size distribution, mechanical properties of the PVDF/TiO2 membrane have significantly improved. But for the PVDF/MWCNTs membrane, when MWCNTs content was 0.5 wt%, the performance of the PVDF/MWCNTs membrane was optimal. FESEM showed that the surface structure of PVDF/TiO2 and PVDF/MWCNTs composite membranes was constituted of spherical microparticles and the diameter of these microparticles decreased with the increasing of TiO2 and MWCNTs content.In this work, the influences of PVDF concentration on the structure and performance of PVDF/MWCNTs membranes were investigated through FT-IR spectra, Wide-angle X-ray diffraction (WXRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM) and water contact angle. The results showed that the contact angle of PVDF/MWCNTs composite membrane was increased from 98.1° to 143.6° and the crystallinity of PVDF/MWCNTs composite membrane was improved from 15.8% to 23.8%. The XPS analysis clearly indicated that more MWCNTs were remained at the surface of modified membranes. FESEM show that the structure of the PVDF/MWCNTs composite membranes was constituted of spherical microparticles and the diameter of these microparticles decreased with the increasing of PVDF content.