有机酸增效光催化降解水中罗硝唑药物研究

发布时间：2018-02-11 09:59

本文关键词： 有机酸罗硝唑光催化协同效应降解机理　出处：《广西大学》2017年硕士论文　论文类型：学位论文

【摘要】：硝基咪唑类药物是一种广泛用于禽畜和人类疾病预防和治疗的抗生素药物,过量使用硝基咪唑类药物导致其在水体和食品中频繁检出。研究表明硝基咪唑类药物具有基因毒性,且能致畸、致癌和致突变,严重威胁着人类健康。因此,对于废水中硝基咪唑药物进行有效的污染控制具有十分重要的意义。光催化技术是一种高效的高级氧化技术,具有反应条件温和,无二次污染等优点,被广泛应用于有机污染物的去除。然而光催化过程中的光生空穴和电子对的快速复合降低了光催化反应效率,同时粉体TiO_2光催化剂难于回收且无法利用可见光限制了光催化技术的实际应用。本文以罗硝唑(RNZ)为硝基咪唑类药物的代表物,系统开展以下研究:为了抑制TiO_2光生空穴和电子对的复合,提高光催化效率,通过在TiO_2体系中加入有机酸作为电子供体的方法有效促进了罗硝唑的降解效率。以紫外灯为光源,以P25为光催化剂,开展了不同有机酸对光催化降解罗硝唑的影响研究,并探讨有机酸的增效机制。研究结果表明,罗硝唑的降解受草酸浓度、溶液pH、有机酸结构的影响。不同有机酸对光催化降解罗硝唑的协同增效作用顺序为:乳酸洒石酸≈苹果酸柠檬酸草酸,仅含有单一羧基或羟基的有机酸或醇作为电子供体不能促进罗硝唑的光催化降解效率。TiO_2+草酸体系中的主要活性物质为(CO2·-和e-,罗硝唑在TiO_2+草酸体系中主要有2条降解途径:一为氮杂环上的双键断裂形成脂肪族化合物;二为杂环支链上的硝基、氨基经过转换聚合生成偶氮化合物,而后C-O键断裂。另外,为了有效解决粉体光催化剂难于回收的问题,且将催化剂的光响应范围扩展至可见光区域,采用溶胶凝胶法制备了Fe2O3@TiO_2@HGMs催化剂,对其进行能谱分析(EDS)、X射线衍射(XRD)、X射线光电子能谱分析(XPS)和紫外可见漫反射(UV-Vis DRS)表征。以氙灯为光源,在有机酸存在下,详细研究了降解条件对罗硝唑去除效率的影响,并对降解机理进行探讨。研究结果表明,Fe和Ti成功地负载在空心玻璃微珠表面,并分别以Fe203和TiO_2的形态存在。Fe203@TiO_2@HGMs复合材料不仅提高了紫外光区域的吸收能力,还拓宽了光的吸收范围。溶液初始pH值对罗硝唑降解的影响较大,随着溶液pH值的升高,罗硝唑的降解速率明显下降。有机酸存在对体系降解罗硝唑具有协同增效作用,则必须满足以下2个条件:(1)所添加的有机酸能与Fe(Ⅲ)形成配合物;(2)Fe(Ⅲ)-有机酸必须在可见光条件下有光反应活性。在草酸和Fe2O3@TiO_2@HGMs体系中,·OH为主要的活性物质,CO2·-起辅助作用。研究发现此体系能自生成H202,同时发生光芬顿和光催化反应,有效提高了罗硝唑的去除效果。有机酸增效Fe2O3@TiO_2@HGMs去除罗硝唑主要有3条降解路径:一为罗硝唑支链上的NH2与杂环上两个N之间的C原子成键形成新的杂环产物(3-乙酰-2-恶唑烷酮);二为罗硝唑杂环上的碳氮双键断裂形成开环产物;三为杂环支链断裂后生成聚合产物。最后中间产物进一步转化生成CO2和H2O。
[Abstract]:Nitroimidazole is a kind of widely used antibiotics in livestock and human disease prevention and treatment, excessive use of nitroimidazole drugs lead to the frequently detected in water and food. The research showed that if nitroimidazole has genetic toxicity and teratogenic, carcinogenic and mutagenic, a serious threat to human health. Therefore, for nitroimidazole drug wastewater for effective pollution control has a very important significance. The photocatalytic technology is an efficient and advanced oxidation technology, has the advantages of mild reaction conditions, no two pollution, has been widely used in the removal of organic pollutants. However, the photocatalytic process of photogenerated electron and hole on the composite reduce the efficiency of photocatalytic reaction, and TiO_2 powder photocatalyst is difficult to recycle and use the actual application limit of visible light photocatalytic technology. This paper take the ornidazole (RNZ As the representative) nitroimidazoles, carried out the following studies: TiO_2 system in order to suppress the photogenerated electron and hole on the composite, improve the photocatalytic efficiency by adding organic acid in the TiO_2 system as the electron donor to effectively promote the degradation efficiency of ronidazole. Under UV light with P25 as a photocatalyst, carried out research on the influence of different organic acids on the photocatalytic degradation of ronidazole, and to investigate the synergistic mechanism of organic acids. The results show that the degradation of ronidazole by oxalic acid concentration, solution pH, influence of organic acid structure. The synergistic effect of different organic acids sequence on the photocatalytic degradation of ronidazole the lactic acid tartaric acid, malic acid and citric acid oxalic acid, organic acid or alcohol containing only a single carboxyl or hydroxyl groups as electron donor cannot promote the main active substances ronidazole the photocatalytic degradation efficiency of.TiO_2+ in oxalic acid system for (CO 2 - and e-, ronidazole has 2 main degradation pathway in TiO_2+ in oxalic acid system: one is breaking on the formation of heterocyclic aliphatic compounds; nitro heterocyclic branched chain amino 2, converted polymerized azo compounds, and the breaking of C-O bonds. In addition, in order to solve the difficulties in the recovery of powder photocatalyst the problem, and the catalyst light response extended to visible light region, Fe2O3@TiO_2@HGMs catalyst was prepared by sol-gel method, the energy spectrum analysis (EDS), X ray diffraction (XRD), X ray photoelectron spectroscopy (XPS) and UV Vis diffuse reflectance (UV-Vis DRS) to characterize. Xenon lamp as light source, in the presence of organic acids, the effects of degradation conditions on the removal efficiency of ronidazole is studied in detail, and the degradation mechanism were discussed. The results show that the Fe and Ti successfully loaded on the surface of hollow glass bead, and using Fe203 and The morphology of TiO_2.Fe203@TiO_2@HGMs composite materials not only improves the ability to absorb ultraviolet region, broaden the range of light absorption. The initial pH value of the solution has great influence on the degradation of ronidazole, with the increasing of pH value, the degradation rate of ronidazole decreased significantly. The organic acid has synergistic effect on the degradation of Luo ornidazole, you must meet the following 2 conditions: (1) organic acid added with Fe (III) complexes; (2) Fe (III) - organic acid must be under visible light. The reaction activity of oxalic acid and Fe2O3@TiO_2@ HGMs system, OH is the main active material CO2, - play a supporting role. It was found that the system can self generate H202, Covington and the photocatalytic reaction occurred at the same time, effectively improve the removal effect of ronidazole. Organic acid enhanced Fe2O3@TiO_2@HGMs removal ronidazole has 3 main degradation paths: Luo nitrate NH2 and the heterocyclic triazole branched between two N C atoms form new heterocyclic products (3- acetyl -2- oxazolidinone); carbon nitrogen double bond fracture for ronidazole on the formation of heterocyclic ring opening products; three is generated after the polymerization product of heterocyclic side chain. Finally, the intermediate product was further transformed into CO2 and H2O.

【学位授予单位】：广西大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X703

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