【作者】 王婵婵；

【导师】 杨凤林；

【作者基本信息】 大连理工大学 ， 化学工程与技术， 2010， 博士

【摘要】 膜生物反应器(membrane bioreactor, MBR)在污水处理过程中得到广泛的应用。然而,膜污染是当前限制MBR广泛应用的主要瓶颈。有必要开发廉价抗污染的膜材料,这对于膜的长期稳定运行以及MBR的推广应用具有重要意义。本研究从膜生物反应器中膜污染的特点出发,开发新型膜材料,以三种亲水性物质改性聚丙烯无纺布膜(Non-woven, NWF),使其具有亲水和抗菌的性能。(1)采用聚乙烯醇(polyvinyl alcohol, PVA)为原料,制备亲水、抗菌的4-乙烯吡啶(4-vinylpyridine,4VP)接枝聚乙烯醇共聚物(PVA-g-4VP),通过涂覆、交联法将共聚物固定在NWF的内外表面。PVA-g-4VP共聚物制备的适宜条件为：PVA浓度为8 g/L,4VP浓度为0.16 mol／L,引发剂浓度为4 mmol／L,反应时间为240 min,温度为60℃。通过对共聚物进行物理和化学分析,发现PVA-g-4VP共聚物可以作为一种适宜的成膜材料对NWF进行改性。在NWF表面吸附PVA-g-4VP共聚物并进行交联后,得到了涂层均匀的复合膜。复合膜的亲水性增加,抗污染性明显增强。对基膜和复合膜的抗菌性能分析表明,复合膜能有效地抑制细菌在膜表面的吸附。复合膜能够有效地阻止生物膜的形成,不可逆污染减轻。(2)对NWF基膜进行臭氧预处理以降低表面张力,在基膜表面涂覆亲水、抗菌的天然高分子聚合物——壳聚糖,通过戊二醛使壳聚糖活性层和臭氧处理过的基膜发生交联反应以增强牢固性。结果表明：复合膜表面光滑,孔径和孔隙率降低；复合膜的亲水性增强；通过活／死细菌染色法评价了复合膜的抗菌性能,复合膜表面细菌吸附量小具有优异的抗微生物污染能力,其中,交联复合膜的抗菌能力更为优异。为了使膜具有长期的抗污染能力,对涂覆方法进行了改进,在膜外表面和膜孔内表面进行同时涂覆。结果表明：动态涂覆法制备的壳聚糖／NWF复合膜亲水性明显增强,复合膜可有效抑制蛋白质的吸附,在MBR中的运行结果表明,复合膜抗不可逆污染能力明显增强；复合膜不仅具有优异的渗透能力,截留性能也有所增强。(3)通过原子转移自由基聚合的方法,在基膜表面接枝甲基丙烯酸-β-羟乙酯(HEMA)聚合物以形成刷状结构。结果表明：ATRP方法能够独立、精确地控制HEMA聚合物链在改性膜表面的长度和密度,并在膜表面和孔内均匀的形成聚合物薄层。纳米刷的长度可以通过控制接枝反应温度和接枝反应时间来调节。聚合物链密度可以通过控制接枝反应时间和臭氧处理时间来调节。纳米刷改性膜具有优异的抗污染性能。纳米刷的长度和密度是影响抗污染性能的关键因素,且接枝链长度的影响比密度的影响大。更多还原

【Abstract】 Membrane bioreactors (MBRs) have been widely used in wastewater treatment. But a major obstacle for the application of MBRs is the rapid decline of the permeation flux as a result of membrane fouling. Thus, developing antifouling and low cost membrane material is necessary. It is essential for steady application of membrane and development of MBR.In this work, novel membrane materials, which were fabricated by modification the non-woven (NWF) with three hydropilicity materials, were developed according to the fouling characteristics in MBR.(1) Synthesis functional polyvinyl alcohol(PVA)/4-vinyl pyridine(4VP) copolymer using Ce(IV) as initiator. The appropriate reaction condition was:PVA concentration of 8 g/L,4VP concentration of 0.16 mol/L, Ce(IV) concentration of 4 mmol/L, reaction time of 240 min and reaction temperature of 60℃. Preparation of novel NWF composite membrane based on polyvinyl alcohol/4-vinyl pyridine copolymer was carried out by adsorption on polypropylene non-woven fabric (NWF) membrane surface and pore walls to improve both hydrophilic and antibacterial properties of the membrane. Experiment results demonstrated that surface properties, both physical and chemical characteristics of the modified membrane, were significantly altered. The results showed that the PVA-g-4VP modified membrane had hydrophilic and strong antifouling properties. Furthermore, antibacterial property of modified membranes were investigated by Live/Dead staining, which results indicated that there was less bacteria attachment on the PVA-g-4VP modified membranes, and the modified membranes surface was thus demonstrated to be very effective in preventing biofilm formation.(2) A novel NWF composite membrane was prepared by ozone pretreatment, chitosan coating and glutaraldehyde crosslink to resist the adsorption of proteins and the adhesion of bacteria. Experiment results demonstrated that the surface morphology and both physical and chemical characteristics of the composite membrane were significantly altered. The results showed that the composite membrane had hydrophilicity and higher protein rejection. Furthermore, antibacterial property of the composite membranes were investigated by staining, which results indicated that there was less bacteria attachment onto the composite membranes, and the composite membranes surface was thus demonstrated to be very effective in preventing biofilm formation, especially for the membrane with glutaraldehyde crosslink. In order to enhance the stability of composite membrane, preparation of porous composite membranes through chitosan crosslinking on/in the NWF outer and internal surface was carried out. The antifouling characteristics of the composite membranes in the submerged membrane bioreactor were investigated. The composite membranes showed better filtration behaviors in MBR than the original NWF membrane. The antifouling property of the modified membranes in the MBR was enhanced. The irreversible fouling resistance decreased.(3) Tailoring of NWF membranes surface properties via surface-initiated atom transfer radical polymerization with 2-hydroxyethyI methacrylate (HEMA) as monomer was carried out. The length and density of the grafted HEMA polymer chains, which form a uniform layer in the membrane pores, can be independently controlled. The length of grafted HEMA polymer chains can be regulated by changing the grafting temperature and grafting time. The density of grafted HEMA polymer chains can be regulated by adjusting the reaction time of ozone treatment on membrane surface. Both the length and density of grafted HEMA polymer chains were key factors for obtaining PHEMA-grafted membranes with desired antifouling properties, and the influence of the length of grafted PHEMA chains was more significant than that of the density. The results can provide valuable guidance for designing and fabricating antifouling membranes with grafted functional polymer.更多还原