【作者】 王萌；

【导师】 王遵尧； 耿金菊；

【作者基本信息】 南京大学 ， 环境工程（专业学位）， 2014， 硕士

【摘要】 偶氮活性染料在整个印染行业中占据重要地位,活性黑5(RB5)染料是其中最具代表性的黑色染料之一,并由于其被大量应用而广泛存在于各类水体环境中,不仅影响水体色度等表观指标,还可能对人体及水生生物造成毒性危害。臭氧氧化技术作为高级氧化技术(AOPs)能通过臭氧分子的分解等反应生成以羟基自由基为主要反应物种的各种强氧化性自由基来去除水体中的有机污染物。本文进行了水溶液中臭氧氧化降解活性黑5染料过程中包括染料初始浓度、臭氧投入剂量以及反应体系pH值在内的各种操作参数对降解速率的影响研究。依此确定了后续鉴定降解产物与降解途径的实验所采用的主要反应条件：染料初始浓度200mg/L,臭氧剂量3.2g/h,最佳反应pH值为8.0,反应温度为25℃。采用反相高效液相色谱与质谱联用(离子阱质量检测器-负离子模式下的电喷雾离子化)技术鉴定主要降解产物。在质谱检测的同时,利用DAD检测器对产物进行了UV-vis光谱扫描。根据保留时间,质谱谱图,UV-vis光谱扫描以及染料母体分子结构等相关信息,确定了臭氧降解RB5过程中主要降解产物的结构,推断出可能的降解路径。主要的降解产物包括生成的检出质荷比m/z为281,546,201,350,286以及222的化合物等,这些降解产物的生成也表明了偶氮键断裂以及随后发生在相应位置的羟基基团加成反应是最为主要的降解机制,同时,长链硫酸酯基及萘环处磺酸基的脱离也是臭氧降解过程中非常重要的反应途径之一。另一方面,本文还进行了以分子轨道模拟为基础的前线电子密度(FEDs)的理论计算研究工作,以期进一步解释水溶液中臭氧降解RB5的降解机制。其中前线电子密度计算是依托于Gaussian09软件程序,利用了DFT/B3LYP方法结合6-31G*基组而完成的。根据前线轨道理论,分子中具有最高FED2HOMO+FED2LUMO值的原子所处位点是最有可能受到羟基自由基进攻的位点,依此推测臭氧降解RB5降解产物的具体分子结构与降解路径。理论计算的预测结果能够很好得解释LC-MS等实验检出结果,表明利用本文所采用的理论计算方法来解释臭氧降解RB5整过程的主要反应途径具有可行性与可操作性。此外,在本文中还进行了利用离子交换色谱通过与标准品对比分析反应前后溶液中硫酸根离子、硝酸根离子以及三种有机酸离子(草酸根、甲酸根以及醋酸根离子)含量变化的相关工作。为评估经臭氧降解后反应体系的矿化程度,测定了反应不同时间后溶液的总有机碳(TOC)含量,为评估臭氧处理后染料溶液的毒性变化情况,根据国家标准(GB/T15441-1995)中规定的发光细菌法测定化合物的急性毒性标准,测定了发光细菌在染料溶液中的相对发光强度抑制率。更多还原

【Abstract】 Azo dyes play an important role in the printing and dyeing industry, C.I. Reactive Black5(RB5) is one of the most representative black dyes. Because of the extensive applications, RB5widely exist in all kinds of the aquatic environment, may cause toxicity to human body and aquatic organism. Ozonation treatment of RB5as advanced oxidation processes (AOPs) which is characterized with the ability to use the high reactivity of hydroxyl radicals in driving oxidation process was investigated in aqueous solution at the initial pH8.0with an initial RB5concentration of200mg/L, using ozone dose of3.2g/h with reaction temperature of25℃, by our study of the influence of various operating parameters on the degradation rate. Reversed-phase high performance liquid chromatography coupled with negative-ion electrospray ionization mass spectrometry is applied for the identification of the major ozone degradation products. In addition, a diode-array detector (DAD) was placed before the mass analyzer to provide UV-vis spectra of the products in the same run. With retention times, mass spectra, UV-vis spectra and the knowledge of the structure of the original dye, it is feasible to propose probable structures of the degradation products by the ozonation treatment. RB5degradation pathways mainly included the conversion of the initial dye to simpler molecules with m/z281,546,201,350,286and222, indicating that the cleavage of the azo bond and introduction of OH groups in the corresponding positions are the predominant reaction mechanism, meanwhile, suggesting the loss of sulfate esters or sulfonic acid groups is a common reaction during the ozonation treatment. The probable degradation mechanism of RB5in aqueous solution was proposed on the basis of the experimental results and verified by the molecular orbital calculation of frontier electron densities (FEDs) by DFT/B3LYP method with6-31G*basis set using Gaussian09program package. According to frontier orbital theory, those atoms with the highest FED2HOMO+FED2LIMO value were the most vulnerable to hydroxyl radical attack, thus we were able to conjecture the configuration of the degradation products and furthermore the ozone oxidation pathway of RB5. The theoretical prediction is in satisfactory agreement with the LC-MS results, indicating there is the feasibility and operability to predict the major events during the whole ozone oxidation of RB5, no longer just the initial oxidation stage. Moreover, sulfate ion, nitrate ion and three carboxylic acids, i.e., oxalic acid, formic acid, and acetic acid were identified using ion exchange chromatography by comparison with authentic standards. In order to assess the extent of mineralization, the reduction of total organic carbon (TOC) during ozone degradation of RB5was also investigated. In order to evaluating the toxicity change of dye solution after ozone treatment, we measured the luminescent bacteria inhibition rate in the dye solution, in accordance with the national standard of determination of acute toxicity by luminescent bacteria method (GB/T15441-1995).更多还原