【作者】 白雪；

【导师】 李彦锋；

【作者基本信息】 兰州大学 ， 高分子化学与物理， 2010， 博士

【摘要】 本学位论文综述了聚乙烯醇(PVA)材料作为固定化载体用于水处理的研究进展,并对目前研究现状与存在的问题进行了评述,提出了本学位论文的选题指导思想。应用反相悬浮交联法将纳米Fe0固定在PVA微球上,通过是否加入分散剂这一条件制备了两种不同尺寸的Fe0／PVA微球。Fe0／PVA微球降解硝基苯模拟废水遵循准一级反应动力学。其标准化表面速率(kSA)值,L-Fe0／PVA微球为0.162L h-1 m-2,S-Fe0／PVA微球为0.098 L h-1 m-2,未固定的纳米Fe0粒子为0.023 L h-1m-2。同时,通过用GC-MS分析反应产物,提出了Fe0／PVA微球还原降解硝基苯的可能途径。L-Fe0／PVA微球中铁离子的回收率为81.17%,S-Fe0／PVA微球铁离子的回收率为60.31%。使用不同浓度的环氧氯丙烷对PVA泡沫载体进行交联,应用载体的溶胀性测定其链间平均分子量,交联密度和链间距离。研究了不同交联浓度的PVA泡沫载体的热性能,比表面积和渗透系数。载体固定生物量和活性产率分别通过测定蛋白质浓度和溶解氧消耗速率求得。TG和DSC分析表明,随着交联度增加,载体的热稳定性增加,结晶度减少。载体固定生物量随交联密度的增大而增大,最高固定生物量为0.0638±0.0093 g VSS g-1载体。然而,生物活性回收率却随着交联密度的增大而减小,最高值为69.38%。通过交联聚乙烯醇泡沫(CPVAF)载体与传统的聚乙烯醇(TPVA)固定化微生物载体的比较可知,CPVAF有更好的化学和热稳定性,更大的比表面积和渗透系数。两种载体固定化硝化细菌的实验表明：CPVAF载体固定的生物量较TPVA载体更大且生物活性更高。在固定生物量相同的条件下,CPVAF载体固定化硝化菌的硝化速率更高,这是由于基质和氧气在载体和溶液间具有更加优异的传质能力所致。通过向载体中加入致孔剂(碳酸钙)改进的传统聚乙烯醇-硼酸法,制备大孔PVA球状载体(MPC),并与戊二醛交联,研究不同交联度载体的孔体积,孔结构,孔隙率和持水倍率。根据载体的溶胀性,应用Flory方程计算载体的交联度。MPC载体显示出较高的溶胀性,比表面积,渗透系数,以及化学和机械强度。高交联度载体固定的生物量较高但活性低,反之亦然。MPC载体的优良特性使得其在微生物固定化领域具有巨大的应用潜力。同时,本论文提供了一个固定化载体设计和优化的科学方法。更多还原

【Abstract】 The preparations of poly(vinyl alcohol) (PVA) carrier for microorganism immobilization and their improved methods are introduced. The processes on immobilized microorganism by PVA carrier for wastewater treatment is reviewed. The research orientation of PVA carrier preparation and development prospects in wastewater treatment are pointed out. Nanoscale Fe0 was immobilized in and on PVA microspheres by the inverse suspension crosslinked method. Two different sizes of Fe0/PVA microspheres were synthesized in the presence and absence of dispersant. The nitrobenzene (NB) reduction reactions followed pseudo-first-order kinetics. The normalized surface rate constants (kSA) values were determined to be 0.162 L h-1m-2 for L-Fe0/PVA microspheres,0.098 L h-1m-2 for S-Fe0/PVA microspheres, and 0.023 L h-1m-2 for nanoscale Fe0 particles. Furthermore, with the analysis of the products by GC-MS, possible reductive pathways of NB by Fe0/PVA microspheres were suggested. The recovery rates of iron in microspheres were determined to be 81.17% for large Fe0/PVA and 60.31% for small Fe0/PVA。Macroporous PVA foam using epichlorohydrin as crosslinking agent was investigated. The average molecular weight among crosslinks, crosslinking density, and mesh size was determined through the equilibrium swelling theory. The characterization of foams with different crosslinking ratios was also investigated by testing thermal properties, specific surface areas, and diffusion coefficients. The biomass densities and activity yields were measured by detecting protein concentration and oxygen uptake rate. TG and DSC tests showed an increase in thermal stability and a decrease in polymeric crystallinity with increasing crosslinking ratio. The biomass densities increase along with the increase in the crosslinking ratio,with the highest value shown at 0.0638±0.0093 g VSS g-1 carrier. However, the activity yields decrease with the increase in the crosslinking ratio, showing the highest value at 69.38%.The crosslinked PVA foam (CPVAF) carrier demonstrated better chemical and thermal stability, as well as larger specific surface area and diffusion coefficients than the traditional PVA (TPVA) carrier. Nitrifying bacteria were used to test the suitability of CPVAF and TPVA carriers for immobilized microorganisms. CPVAF carriers supported higher biomass density and microbial activity than TPVA carriers. At the same biomass density, the higher nitrification rate of CPVAF carriers was attributed to excellent mass transfer of the substrate (and oxygen) between the bulk solution and the immobilized microorganisms.The traditional PVA-boric acid method was modified using calcium carbonate as a pore-forming agent to form the macroporous structure and formulated macroporous carrier (MPC) post crosslinked with glutaraldehyde. The pore volumes, pore structure, porosity, and swelling behavior of MPCs were evaluated. The crosslinking density of MPCs with four different crosslinker dosages was calculated from their swelling properties using the modified Flory equation. MPCs demonstrated high swelling capacity, large specific surface area, high diffusion coefficient, as well as chemical and mechanical strength. The high crosslinking degree MPCs resulted in high biomass densities and low activity yield and vice versa. The characterizations of MPC suggest significant potential of its use for microbial immobilization and provide a scientific basis for immobilized carrier design and optimization.更多还原