【作者】 朱遂一；

【导师】 霍明昕；

【作者基本信息】 东北师范大学 ， 环境科学与工程， 2011， 博士

【摘要】 光催化技术能够有效解决水中多种人工合成有机物的持久性污染问题,其与生物处理技术的联合应用在污水处理领域展现出明显的优势。然而,受粉体光催化剂使用过程中回收困难,且光催化氧化耗时长、能耗大等问题,限制了其在实际工程中的应用。众多研究显示,难降解有机物经过光催化处理后,其出水仍具有一定的微生物抑制性。据此,本项目以典型化工原料喹啉为研究对象,利用光催化技术与生物处理技术相结合,系统研究了光催化材料制备、喹啉的光催化降解行为及其出水对活性污泥的影响,主要成果如下:以制备磁分离型粉体催化剂为目标,采用沉积-沉淀法在纳米Fe₃O₄表面负载Au颗粒,制备了系列FeO_x/Au催化剂。经过煅烧后部分Fe₃O₄被氧化生成α-Fe₂O₃提高了光催化活性,但仍具有良好的磁分离效果。表面负载Au能够增强FeO_x/Au的光催化活性,但其对水中喹啉的降解速率明显低于Deguessa P25 TiO₂。在不加粘结剂的前提下采用浸渍涂布法在多孔镍基片上负载P25 TiO₂,制备成一种多孔镍基P25薄膜。保持负载浓度为10 wt.%时制备的P25薄膜具有最佳的光催化活性,其原因是薄膜具有大比表面积和多孔结构,表面存在大量微裂痕,而且热处理并没有明显改变P25 TiO₂的晶相,并促使基片上Ni以金属镍和氧化镍共存体（比例为12 at.%）扩散到薄膜表面。相应地,以10 wt.%浓度制备的P25薄膜为光催化组件,设计并制作了一种连续流内循环光催化反应器,分别考察了初始浓度、光照时间、光强、曝气量等条件下对水中喹啉去除效果的影响。结果表明:增大光照强度、曝气量和延长反应时间能够明显提高水中喹啉的光催化降解率,反应温度和初始浓度不是主要的控制步骤。保持初始溶液pH=4时水中喹啉的去除效率最高。水中喹啉的光催化降解符合Langmuir- Hinshelwood动力学模型,这说明水中喹啉的光催化氧化过程主要发生在P25薄膜的表面,光生电子-空穴派对的直接还原和氧化是水中喹啉初步降解的主要步骤。增大初始浓度有助于提高水中有机物的去除率,但会降低喹啉的去除速率,这主要是受产物竞争吸附和竞争氧化自由基的影响;水中喹啉的降解活化能为16.9kJ/mol,表观吸附常数为0.024 L/mg。水中喹啉光催化降解动力学的表达式为: r_a=0.35×10^-3exp（-16906/RT）I_a^0.53×1.29C₍o2_/(1+1.29C_o2)×0.024C_q/(1+0.024C_q0)HPLC和GC/MS分析结果显示喹啉光催化降解产物中包括2-和3-吡啶甲醛、2-和3-乙酰吡啶以及2-羟基喹啉。在有氧条件下TiO₂表面的喹啉存在一条可能的降解途径:首先是TiO₂吸附氧分子的接受光生电子生成O₂^-,其在水相中具有一定的存活时间从而可以参与喹啉的光催化过程,其吸收的光生电子向TiO₂表面活性点位释放时,也会出现向相邻吸附位置的喹啉分子中-2位释放,从而在-2位引入氧基并在氧化物种作用下生成2-羟基喹啉,这样增大了吡啶环上-3位电荷密度促使该点位被氧化,最终导致吡啶环在2,3-位开环,生成一系列苯系物。以活性污泥为受试物,检验了喹啉光催化降解30min和60min时,对可培养细菌和酶活性的影响,结论显示光催化降解30min出水不利于活性污泥中可培养细菌的生长,受总生物量降低的影响,脱氢酶、蛋白酶活性明显下降。喹啉水溶液经过60min光催化降解后,并没有抑制水中细菌的生长,活性污泥中存在土著菌群具有专性降解或共代谢降解喹啉及其中间产物的特性。进一步构建连续流光催化-生物处理组合实验模型,研究了喹啉水溶液的降解过程,当光催化降解时间为60min时,组合系统出水中CODCr值保持在50mg/L左右,具有稳定的去除效率。当降解时间调整为30min时,出水CODCr值上升到90mg/L,且出水呈现粉红色。最后利用PCR-DGGE技术分析了喹啉水溶液光催化氧化后对活性污泥中微生物群落结构的影响,结果显示光催化30min的喹啉水溶液对活性污泥中微生物具有抑制性,微生物物种多样性下降,未培养细菌Clostridium sp.适应低营养基质条件使种群数量增大,而Sphingopyxis granuli sp.能够优先利用或共代谢喹啉水溶液光催化出水中的有机物从而发育成为新的优势种群,其作为可培养土著细菌可以直接从活性污泥中筛选并获得具有高效降解性的纯菌株。更多还原

【Abstract】 Persistent pollution of multiple artificially synthesized organic compounds could be effectively solved by photocatalytic technology, while its combined with biological treatment technique shows a optimum advantage in the wastewater treatment. However, there exist some problems limit its application in practice, such as the difficult of recycled powder catalyst, the long time oxidation and high energy consumption, and so on. A great deal of lab-scale research proved that the wastewater contained many refractory organic matter still has inhibitory effect on microorganism after photocatalytic oxidation. Therefore, this research present an introduction of two photocatalysts, a newly three-dimensional photocatalytic reactor and a combined treatment of photocatalysis and biological technology. As a typical chemical raw material, quinoline, which contains a fused-ring result in hardly biodegradation, was selected for the research target. The research mainly aimed at the preparation of photocatalyst, photocatalytic degradation behavior and the biological effect of photocatalytic effluent. The main results are summarized as follow:In order to synthesize a segragative powder photocatalyst, nanomater Au was coated on the surface of superparamagnetic iron oxide （SPIN） to prepare a FeO_x@Au photocatalyst by a facile deposition-precipitation method. Although part of SPIN was oxidized intoα-Fe₂O₃ after calcination, the FeO_x@Au also remains a favorable effect of magnetic separation. What’s more, it displays a high photocatalytic activity for the degradation of quinoline aqueous solutions. Nano-Au loaded on the surface of SPIN could enhance the photocatalytic activity, while the degradation efficiency of quinoline was also lower than Deguessa P25 TiO₂.A kind of P25 TiO₂ films was synthesized by dip-coating/calcination route in situ without any binder. The porous nickel coated with 10 percent of P25 sol （named Ti-10） had an optimal photocatalytic activity for the degradation of quinoline aqueous solutions, which was attributed to porous surface structure fabricated by nano-sized titanium dioxide consisted of two crystal phase and incorporated with a NiO interlayer formed during calcination.Accordingly, Ti-10 film was used to fabricated a newly continuous-flow three-phase photocatalytic reactor. The effect of initial concentration, reaction time, light flux and aeration on the efficiency of photodegradation were also investigated. The result indicated that the photocatalytic efficiency could be significantly enhanced by increacing the light intensity, aeration and reaction time. The optimum pH value for quinoline degradation was at 4 and neither the initial concentration nor temperature was the primarily factors for the photocatalytic reaction.The second-order decomposition rate of quinoline may be approximately expressed in the terms of Langmuir-Hinshelwood kinetics, which indicated that the photooxidation of quinoline mainly occured on the surface of P25 film. So, the direct reduction and oxidation of photo-induced electron and hole were the predominant process of the innitial degradation of quinoline. Increasing the initial concentration of quinoline in water may led to the enhancement of decomposition efficiency of organic matter and the decrease of photooxidation rate of quinoline in water, which was mainly attributed to the influence of competitive sorption between the product and quinoline or free radicals on the film surface. The photocatalytic kinetics was obtain with the follow equation: r_a=0.35×10^-3exp（-16906/RT）I_a^0.53×1.29C₍o2_/(1+1.29C_o2)×0.024C_q/(1+0.024C_q0)Here, the overall apparent activation energy was 16.9 kJ/mol, while the rate constant of apparent adsorption was 0.024 L/mg.A number of intermediates were identified by the combined method of HPLC and GC/MS techniques during the photooxidation process of quinoline, include 2- and 3-Pyridinecarboxaldehyde, 2- and 3-Acetylpyridine and 2-（1H）-Quinolinone. A possible photooxidation pathways can be observed in aerobic conditions. At first, photo-induced electron quickly reduced the oxygen molecules absorbed on the TiO₂ surface with the formation of O₂-. The activated oxygen species generated on the TiO₂ surface can participate the photo-reduction process of quinoline just because it remains active for some time in water, and then released the photo-induced electron to the active sites on the TiO₂ surface. Considering the reaction between quinoline and O₂- an addition to the position -2 of quinoline may take place the same way as for an ordinary deprotonation. Thus, the product derived from deprotonation at position 2 is 2-hydroxyquinoline, which cause the increasement the electrostatic charge density of quinoline and led to easily oxidation by active radicals at position 3. Finaly, it led to ring opening process via quinoline（2,3）dion with the formation of organic compounds with aromatic ring.The effluent from photocatalytic reactor, which photooxidated at 30min and 60 min reaction time seperately, was directly biodegradated by activated sludge with the flask culture method for the determination of the influence on the culturable microbial and enzyme activity. The result showed that the effluent photooxidated for 30 min inhaibited the growth of culturable bacteria in activated sludge and the activity of dehydrogenase and protease was significantly inhabited by the decrease of the total biomass. However, the effluent was not affected the growth of bacteria after photocatalytic oxidation for 60 min, indicated that quinoline and intermediates could be biogradated by native bacteria in activated sludge.An integrated photocatalystic oxidation and biodegradation reactor was successful designed to study the biodegradation of photooxidated effluent from photocatalytic reactor. When the photooxidation reaction lasted for 60 minutes, the chemical oxygen demand of effluent from the intergrated reator remained at about 50mg/L, indicated the stable remove efficency. However, the water becomes pink when the photooxidation reaction time reduced to 30 minutes, and then the chemical oxygen demand of effluent rised to about 90 mg/L.The effect of microbial community structure caused by quinoline aqueous solutions photooxidated for 30 min was analyzed by polymerase chain reaction-denaturing gradient gel electrophoresis technology （PCR-DGGE）. The result showed that the effluent inhibited the microbial activity in activated sludge and led to the decrease of species diversity. Thereafter, in activated sludge, due to the adaptability of low nutrition medium, the community number of uncultured Clostridium sp. increased significantly and becomes one of dominant microflora. Accordingly, Sphingopyxis granuli sp. was believed to preferentially biodegradate or co-metabolish quinoline or it’s by-products and then multiply advantage bacterium group to be a dominant microflora, which is a culturable bacteria with high biodegradation ability could be isolated from sewage activated sludge.更多还原