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A Study on Preparation and Characterization of Inorganic Materials/Poly (Vinylidene Fluoride) Composite Ultrafiltration Membranes

Author: LiaoZuoJuan
Tutor: LuoYunBai
School: Wuhan University
Course: Applied Chemistry
Keywords: Polyvinylidene fluoride Ultrafiltration membrane Inorganic Modified Nano Silica AgNaY zeolite Nano calcium carbonate Nano-zinc oxide
CLC: TQ028.8
Type: PhD thesis
Year: 2011
Downloads: 438
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Abstract

Membrane separation technology is an important high-tech and sustainable development of the technical basis to solve contemporary energy, resources and environmental pollution problems. In China, the variety and quality of the ultrafiltration membrane compared with the international advanced level there is a gap, the ultrafiltration membrane has a major theoretical and practical application. Currently, the direction of ultrafiltration membrane is to improve the film's anti-pollution performance and reduce operating costs. Polyvinylidene fluoride material of high chemical stability, good heat resistance, high strength, good toughness, is the preferred material of the membrane preparation. Ethylene strong hydrophobic polyvinylidene fluoride, polyvinylidene fluoride, ethylene ultrafiltration easily affected by pollution of proteins, oils and other substances in the filtering operation. The membrane fouling a direct result of the film shorten the life of the increase in operating costs, and greatly limits the scope of application of the ultrafiltration membrane. Therefore, the modified polyvinylidene fluoride ultrafiltration membrane is particularly important. Nanomaterials is recognized as one of the focus on the development of new materials. The nano inorganic material and polyvinylidene fluoride (PVDF) combined, not only can concentrate their respective advantages of inorganic materials and organic materials, to compensate for the defects, and the development of a single membrane material not originally performance to meet the specific needs. The topics selected mesoporous silica (SBA-15), nano-powder silica (SiO2), NaY-nano-zeolite molecular sieves, nano calcium carbonate (Nano-CaCO3) and zinc oxide (Nano-ZnO polyvinylidene fluoride) as a modifying material, were prepared by phase inversion method different nanomaterials modified ultrafiltration. Concentration of inorganic nanomaterials on the structure and properties of the modified membrane, and the use of modern instrumental methods and filtering operations on the surface of the modified membrane cross-section morphology structure, thermal stability, mechanical properties, hydrophilic, filtration performance and fouling performance of the research and analysis. Homemade new inorganic nanosized mesoporous silica material SBA-15 by the phase inversion method were prepared by the the PVDF blend of modified membrane containing low concentrations of SBA-15 Particles (≤ 0.72 wt%). By scanning electron microscopy (SEM), X-ray spectroscopy (EDX), tensile strength test, thermal gravimetric analysis (TGA), contact angle measurement, water flux and bovine serum albumin (BSA) rejection of other methods to characterize the modified membrane The nature. Found that the introduction of low concentrations of SBA-15 particles on the surface of the film, the cross-sectional morphology and internal aperture is not significantly affected. Experimental results show that adds a low content of the SBA-15 particles can be effectively improved PVDF ultrafiltration membrane hydrophilic, to improve the contamination resistance, mechanical strength and thermal stability of the membrane, and the membrane flux increases at the same time, to maintain the BSA rejection rate in more than 87%. The comparison the original PVDF ultrafiltration membrane and the two low concentrations of different structures of silica (N-SiO2 and M-SiO2 particles) a blend of polyvinylidene fluoride (PVDF) membrane modified. Compared by measuring the water flux and BSA rejection rate were observed by SEM and atomic force microscopy (AFM), a cross-sectional view of the film and the surface morphology; characterized by the determination of the contact angle of the modified membrane surface a porous hydrophilic properties of the surface of the film; The modified membrane filtration performance; the size of the average pore diameter and porosity of the film obtained based on the permeation flux BSA; characterized by TGA and the elastic tensile force test the thermal stability and mechanical strength of the modified membrane. The results showed that the N-SiO2 and M-phase SiO2 concentration N-SiO2/PVDF (PN) larger average pore size and porosity of the modified membrane, the higher water flux and BSA rejection rate decreased slightly; respect to PN-modified film, the higher hydrophilicity of the surface of the modified membrane M-SiO2/PVDF (PM), a relatively low surface roughness, preferably anti-pollution performance, and PM-modified membrane is relatively higher mechanical strength. In addition, both of the modified membrane having a typical asymmetric membrane morphology and excellent thermal stability. Phase Inversion the blend modified ultrafiltration membrane of a novel antibacterial AgNaY / PVDF (P-AgNaY). AgNaY blend films with excellent and long-lasting antibacterial activity against E. coli. The results show that the stronger the higher the antibacterial activity of the silver ion content. The P-AgNaY,-contact angle was reduced to 81.6 °, film surface hydrophilic improved. With the compared to PVDF original film, the P-AgNaY modified membrane filtration performance, thermal stability and mechanical strength has improved, and the the BSA retention rate in more than 92%. Measured by inhibition zone antibacterial activity of the modified membrane of E. coli and antibacterial long-term. The use of SEM, X-ray diffraction method (XRD), a tensile strength test, TGA, contact angle test and the test of the membrane flux characterized the P-AgNaY various properties of the blend films. Nano-CaCO3 as a dopant material by phase inversion prepared with different concentrations of Nano-CaCO3/PVDF blend ultrafiltration membrane. Discuss the membrane pore structure of the modified membrane, mechanical properties, thermal stability, hydrophilicity and filtration performance. With the increase of Nano-CaCO3 content, the modified membrane in the asymmetric structure of the membrane was maintained at the same time, their porosity and average pore diameter gradually increases, the contact angle of the surface of the film as a whole a downward trend, the hydrophilicity increases, at the same time the modified membrane water flux and anti-pollution performance, increase the thermal stability of the modified membrane. Nano-CaCO3 and the strong hydrophilicity, so that the hydrophobic polyvinylidene fluoride (PVDF) membrane casting solution in the presence of a small amount of aggregates, thereby reducing the degree of dispersion of Nano-CaCO3 particles in the film, when the Nano-CaCO3 concentration is 1.2 wt % when the mechanical strength of better overall performance. Homemade nano-ZnO particles were prepared by phase inversion the different concentrations Nano-ZnO/PVDF blend ultrafiltration membrane. With Nano-ZnO content increased, the contact angle of the modified membrane is gradually decreased, the hydrophilicity of the surface of the film is gradually increased, the porosity has also been increased, thereby increasing the water flux of the PVDF membranes modified when the Nano- The ZnO content of the flux reaches a maximum when 5 wt% of water. ScS type of Nano-ZnO content PVDF membrane modified mechanical strength, Nano-ZnO content is preferably 5 wt%, the mechanical properties of the modified membrane. Adding 5 wt% of Nano-ZnO particles can effectively regulate the membrane pore structure, changing the membrane pore size distribution and the improvement of filtration performance, increase the water flux of the membrane. Nano-ZnO effectively improve the thermal stability of the modified membrane.

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CLC: > Industrial Technology > Chemical Industry > General issues > Chemical processes ( physical processes and physical and chemical processes ) > Separation process > New separation method
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