PVDF超滤膜改性及其应用研究
发布时间：2019-03-16 12:01
【摘要】：膜分离技术是以物质分离、浓缩和提纯为目的的经济、环保、高效的分离手段。目前,聚偏氟乙烯(PVDF)已经是当今世界上应用最广泛的膜分离材料之一,它具有抗氧化活性强,耐化学性优异,热稳定性强,机械强度大,成膜性能良好等优良性能,但由于其表面能低,疏水性强而使其容易受到蛋白质和水处理系统中其他杂质的污染,导致膜通量下降,膜的使用寿命减小,更换成本增加,这就限制了 PVDF膜在水处理领域的应用。因此,PVDF的疏水性成为其在膜技术应用中的主要障碍。为了使PVDF膜更好的运用在污水处理技术中,本文结合共混和原位共沉两种方法对PVDF膜进行亲水化改性,并提出了一种稳定性较好的复合膜制备方法。本研究以聚偏氟乙烯(PVDF)为聚合物,氧化石墨烯(GO)为添加剂,聚乙烯吡咯烷酮(PVP30)为致孔剂,N,N-二甲基乙酰胺(DMAc)为溶剂配制铸膜液,借助相转化法制备了聚偏氟乙烯/氧化石墨烯超滤膜(PVDF/GO,PGM),并通过原位共沉反应在PVDF膜和PGM表面沉积Ag2C03得到Ag2C03@PVDF/GO复合膜(AgC-PGM)和Ag2C03@PVDF复合膜(AgC-PVDF)。选用3种模拟污染物(牛血清蛋白BSA、腐植酸HA和甲苯)对复合膜的基本性能和分离性能进行了考察,并通过膜阻力计算、污染物的静态吸附和修正污染指数(MFI)值比较等评价了复合膜的抗污染性能,同时利用傅立叶红外光谱(FT-IR)、场发射扫描电子显微镜(FESEM)等表征了其微观结构,最后利用校区湖水考察了复合膜对地表水的分离性能,用三维荧光光谱验证了溶解性有机物(DOM)去除实效。结果表明,当添加GO质量为0.4wt.%,AgN03(5.0 mM)与Na2C03(2.5mM)共沉反应3次得到AgC-PGM呈现出了较高的亲水性和纯水通量,与PVDF膜(132.8 L/m2·h)相比,其纯水通量提高了 78.8%,对BSA截留率稳定在75%以上。与PVDF膜相比,复合膜AgC-PGM对水的接触角降低了近10°,亲水性显著增加;对BSA溶液的通量衰减率降低了 45%,通量恢复率增加到近80%;阻力结果显示,复合膜总阻力较PVDF膜有显著降低,且不可逆阻力显著下降,抗污染性能得到提高。通过分离校区湖水发现,AgC-PGM不仅凸显了去除蛋白质和溶解性有机物(DOM)的能力,而且出水COD和UV254均达到了自然水体一级标准,这意味着AgC-PGM是具有高抗污染和高分离性的复合膜材料。
[Abstract]:Membrane separation is an economical, environmentally friendly and efficient separation method for the purpose of material separation, concentration and purification. At present, polyvinylidene fluoride (PVDF) is one of the most widely used membrane separation materials in the world. It has excellent properties such as strong anti-oxidation activity, excellent chemical resistance, strong thermal stability, high mechanical strength, good film-forming properties, and so on. However, due to its low surface energy and strong hydrophobicity, it is vulnerable to contamination by protein and other impurities in the water treatment system, resulting in a decrease in membrane flux, a decrease in the service life of the membrane, and an increase in the replacement cost. This limits the application of PVDF membrane in the field of water treatment. Therefore, the hydrophobicity of PVDF has become the main obstacle in the application of membrane technology. In order to make PVDF membrane better used in wastewater treatment, the hydrophilic modification of PVDF membrane was carried out by blending and in-situ co-precipitation, and a method of preparing composite membrane with good stability was put forward. In this study, polyvinylidene fluoride (PVDF) was used as polymer, graphene oxide (GO) as additive, polyvinylpyrrolidone (PVP30) as pore-forming agent, N, N-dimethylacetamide (DMAc) as solvent. Polyvinylidene fluoride / graphene oxide ultrafiltration membrane (PVDF/GO,PGM) was prepared by phase inversion method. Ag2C03@PVDF/GO composite membrane (AgC-PGM) and Ag2C03@PVDF composite membrane (AgC-PVDF) were prepared by in-situ co-deposition of Ag2C03 on the surface of PVDF and PGM. Three simulated contaminants (bovine serum protein BSA, humic acid HA and toluene) were used to investigate the basic properties and separation properties of the composite membrane, and the resistance of the membrane was calculated. The static adsorption of pollutants and the comparison of the modified pollution index (MFI) values were used to evaluate the anti-fouling performance of the composite membranes. The microstructure of the composite membranes was characterized by Fourier transform infrared spectroscopy (FT-IR) and field emission scanning electron microscope (FESEM). Finally, the separation performance of the composite membrane on surface water was investigated by using the lake water of campus, and the effect of (DOM) removal of dissolved organic matter was verified by three-dimensional fluorescence spectrum. The results showed that when the mass of GO was 0.4 wt.%, Agn03 (5.0 mM) reacted with Na2C03 (2.5mM) for three times to obtain a higher hydrophilicity and pure water flux, compared with PVDF membrane (132.8 L / m ~ 2 路h), the results showed that Agn03 (5.0 mM) reacted with Na2C03 (2.5mM) for three times, showing higher hydrophilicity and pure water flux. The pure water flux increased by 78.8% and the retention rate of BSA was over 75%. Compared with the PVDF membrane, the water contact angle of the composite membrane AgC-PGM decreased by nearly 10 掳, and the hydrophilicity of the composite membrane increased significantly, and the flux decay rate of the BSA solution decreased by 45% and the flux recovery rate increased to nearly 80%. The resistance results showed that the total resistance of the composite membrane was significantly lower than that of the PVDF membrane, and the irreversible resistance was significantly decreased, and the anti-fouling performance of the composite membrane was improved. It was found that AgC-PGM not only showed the ability of removing protein and dissolved organic matter (DOM), but also reached the first class standard of natural water body for COD and UV254 in effluent by separating the lake water from campus. This means that AgC-PGM is a composite membrane material with high anti-fouling and high separation.
【学位授予单位】：天津工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X703
本文编号：2441316
[Abstract]:Membrane separation is an economical, environmentally friendly and efficient separation method for the purpose of material separation, concentration and purification. At present, polyvinylidene fluoride (PVDF) is one of the most widely used membrane separation materials in the world. It has excellent properties such as strong anti-oxidation activity, excellent chemical resistance, strong thermal stability, high mechanical strength, good film-forming properties, and so on. However, due to its low surface energy and strong hydrophobicity, it is vulnerable to contamination by protein and other impurities in the water treatment system, resulting in a decrease in membrane flux, a decrease in the service life of the membrane, and an increase in the replacement cost. This limits the application of PVDF membrane in the field of water treatment. Therefore, the hydrophobicity of PVDF has become the main obstacle in the application of membrane technology. In order to make PVDF membrane better used in wastewater treatment, the hydrophilic modification of PVDF membrane was carried out by blending and in-situ co-precipitation, and a method of preparing composite membrane with good stability was put forward. In this study, polyvinylidene fluoride (PVDF) was used as polymer, graphene oxide (GO) as additive, polyvinylpyrrolidone (PVP30) as pore-forming agent, N, N-dimethylacetamide (DMAc) as solvent. Polyvinylidene fluoride / graphene oxide ultrafiltration membrane (PVDF/GO,PGM) was prepared by phase inversion method. Ag2C03@PVDF/GO composite membrane (AgC-PGM) and Ag2C03@PVDF composite membrane (AgC-PVDF) were prepared by in-situ co-deposition of Ag2C03 on the surface of PVDF and PGM. Three simulated contaminants (bovine serum protein BSA, humic acid HA and toluene) were used to investigate the basic properties and separation properties of the composite membrane, and the resistance of the membrane was calculated. The static adsorption of pollutants and the comparison of the modified pollution index (MFI) values were used to evaluate the anti-fouling performance of the composite membranes. The microstructure of the composite membranes was characterized by Fourier transform infrared spectroscopy (FT-IR) and field emission scanning electron microscope (FESEM). Finally, the separation performance of the composite membrane on surface water was investigated by using the lake water of campus, and the effect of (DOM) removal of dissolved organic matter was verified by three-dimensional fluorescence spectrum. The results showed that when the mass of GO was 0.4 wt.%, Agn03 (5.0 mM) reacted with Na2C03 (2.5mM) for three times to obtain a higher hydrophilicity and pure water flux, compared with PVDF membrane (132.8 L / m ~ 2 路h), the results showed that Agn03 (5.0 mM) reacted with Na2C03 (2.5mM) for three times, showing higher hydrophilicity and pure water flux. The pure water flux increased by 78.8% and the retention rate of BSA was over 75%. Compared with the PVDF membrane, the water contact angle of the composite membrane AgC-PGM decreased by nearly 10 掳, and the hydrophilicity of the composite membrane increased significantly, and the flux decay rate of the BSA solution decreased by 45% and the flux recovery rate increased to nearly 80%. The resistance results showed that the total resistance of the composite membrane was significantly lower than that of the PVDF membrane, and the irreversible resistance was significantly decreased, and the anti-fouling performance of the composite membrane was improved. It was found that AgC-PGM not only showed the ability of removing protein and dissolved organic matter (DOM), but also reached the first class standard of natural water body for COD and UV254 in effluent by separating the lake water from campus. This means that AgC-PGM is a composite membrane material with high anti-fouling and high separation.
【学位授予单位】：天津工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X703
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