【作者】 许银；

【导师】 孙德智；

【作者基本信息】 北京林业大学 ， 生态环境工程， 2012， 博士

【摘要】 为了解决传统湿式催化氧化(简称CWAO)工艺中存在反应条件苛刻、处理成本高和对设备要求严格等问题,本文通过对催化剂的改性研究,实现了可在常温常压条件下通过CWAO工艺有效处理阳离子红GTL染料废水。本文首先对催化剂的载体进行了遴选,采用浸渍方法制备出以Al203、拟薄水铝石、类水滑石和分子筛(4A、5A、13X)为载体、Fe、Mn或者Mo为活性成分的系列催化剂,考察了系列催化剂对阳离子红GTL染料废水的催化活性,优选出以Zn-Al类水滑石为载体、Mo为活性组分的Mo-Zn-Al-O负载型催化剂。XRD和XPS的分析表明,该催化剂中的钼一部分以M002形式存在、一部分与Zn形成ZnMoO4复合金属氧化物,而Al未形成晶体形态,以AlOx形式存在。为了研究载体类水滑石中的二价金属与三价金属的比例对催化剂性能的影响,本文首先采用共沉淀法制备出不同Zn-Al摩尔比的类水滑石,然后采用浸渍法制备出Mo-Zn-Al-O催化剂,并采用多种分析方法对其进行了表征,探讨了不同ZnAl摩尔比对该催化剂的结构及对阳离子红GTL催化活性的影响。研究结果表明,该催化剂中Zn/Al比为1：1时,对阳离子红GTL的脱色率和TOC去除率可分别达90.9%和65.8%,表明具有较好的催化活性,此时,该催化剂具有较低的Zeta电位(-17.5eV)、较大的比表面积(147m2/g)和特殊的晶体结构(ZnMoO4、ZnO和M002)、性质较活泼的Mo=O键、丰富的氧吸附活性位点(31.5a.u./g)及较强的氧化还原性能(Mo6+到Mo5+和Mo5+到Mo4+还原峰)。采用筛选试验设计方法研究了常温常压条件下使用Mo-Zn-Al-O催化剂CWAO降解阳离子红GTL染料废水的影响因素。实验结果表明,在催化降解过程中,影响阳离子红GTL染料降解的主要因素是pH值、阳离子红GTL初始浓度和催化剂用量。在此基础上,分别采用中心组合设计(CCD)、箱线图设计(BBD)、D-最优设计等实验设计方法对CWAO工艺的主要因素pH值、阳离子红GTL初始浓度、催化剂用量等进行优化,实验所得数据进行方差分析后得到相应的二次方程模型,在试验水平范围内,该二次方程模型方差分析得到CCD、D-最优设计和BBD三种设计方法的R2分别为0.97,0.94和0.99,其中经BBD设计优化出的数值更接近实际值,实验操作的最优条件是：pH值为4.5,阳离子红染料GTL初始浓度为284mg/L,催化剂用量为0.97g/L。此条件下阳离子红GTL染料脱色率可达97%。本文以阳离子红GTL染料浓度为284mg/L的废水作为处理对象,研究Mo-Zn-Al-O负载催化剂常温常压下湿式催化氧化过程的动力学。结果表明,该体系反应活化能为-312.36J/mol,反应速率常数为9×10-5。本文利用密度泛函理论方法和GC/MS、FT-IR、挥发酸的测定、自由基的抑制实验和ESR检测等实验手段研究了废水中阳离子红GTL染料经CWAO工艺的降解历程。结果表明,阳离子红GTL首先被吸附在催化剂表面,而催化剂中的活性组分钼离子可催化水中溶解氧生成羟自由基和单线态氧,吸附于催化剂表面的阳离子红GTL染料中的N=N偶氮键在可被羟自由基或单线态氧攻击而断裂,然后苯环结构被破坏,随着反应的进行,中间产物被氧化成已酸、乙醇和碳氢化合物。更多还原

【Abstract】 Catalytic wet air oxidation process requires high temperature and high pressure which lead to high installation costs. In order to solve this problem, the catalyst was prepared and modified, which has ability to treat cationic red GTL dye wastewater under room temperature and atmospheric pressure.Firstly, the carrier of catalyst was selected. Al2O3、pseudoboehmite、LDHs or molecular sieve was as the carrier and Fe, Mn or Mo was as active compound to prepare the catalysts using impregnation method. The results show that Mo-Zn-Al-O catalyst prepared with Zn-Al as the carrier and Mo as active compound had a better catalytic activity. The XRD and XPS characterization results show that a part of Mo was present as MoO2and a part as ZnMoO4. Al was not in the crystal and was present as AlOx.The effect of Zn and Al molar ratio on the catalytic activity was studied to investigate the effect of M2+/M3+ratio in LDHs on the structure of the catalyst. A series of Zn-Al LDHs with different Zn/Al molar ratios were prepared using copreicipitation and Mo-Zn-Al-O catalyst was obtained. The structure of the catalysts was characterized using ICP-OES, Zeta potential, XRD, BET, FT-IR, H2-TPR, and O2-TPD. The catalytic activity of these catalysts on the degradation of cationic red GTL wastewater under room condition was investigated. The experimental results show that the highest color removal efficiency and TOC removal efficiency of cationic red GTL can reach90.9%and65.8%by the Mo-Zn-AI-O catalyst with1:1of Zn/Al molar ratio respectively. Associated with the characterization results of these catalysts, Mo-Zn-Al-O catalyst with1:1of Zn/Al molar ratio with highest catalytic activity could be contributed to its lowest zeta potential (-17.5eV), largest specific surface area (146.98m2/g), special crystalline phases (ZnMoO4, ZnO and MoO2), special Mo valences (reducibility from Mo6+to Mo5+and from Mo5+to Mo4+), largest number of active adsorption sites (31.5a.u./g).The factors in CWAO process on degradation of cationic red GTL were investigated. Application of Plackett-Burman Design and its following statistical analysis indicated that pH value of system, initial cationic red GTL concentration, the amount of catalysts were the three key factors significantly influencing catalytic activity. Considering decolorization efficiency as the response objective, a quadratic model was respectively obtained by Central Composite Design, Box-Behnken Design and D-optimal Design. Base on the analysis of variance, the coefficient of determination of three models were0.97,0.99and0.94repectively. This means that BBD model is closer to reality and97%of decolorization of cationic red GTL in CWAO over Mo-Zn-Al-O mixed oxide achieved. The optimal catalytic conditions were:pH value was4.5, the initial concentration of cationic red was284mg/L and the amount of catalysts was0.97g/L.The kinetic of the CWAO process on the degradation of284mg/L cationic red GTL dye wastewater was investigated. The results showed that the activation energy is-312.36J/mol, Reaction rate constant is9×10-5.The degradation mechanism of cationic red GTL was studied by density fuctional theory and electron spin resonance (ESR), FT-IR, GC-MS, acid measuring through GC, inhibit of radicals experiments and ESR technique. The results show that dye pollutants are adsorbed on the surface of catalysts by a hydrogen bonding interaction between hydroxyl groups and O atoms. The Mo-Zn-Al-O catalyst can efficiently react with adsorbed oxygen/H2O to produce·OH and’O2. Azo bond of cationic red GTL adsorbed on the surface of catalyst is relatively easier to be attacked by free radicals in CWAO process. Once the-N=N-bond is broken, the color of dye is removed. After azo bond were attacked, the free radicals continued to react with the intermediates. With the continuous oxygen and the reaction time, these intermediates can be oxidized to acid, aldehyde, alcohol and hydrocarbons.更多还原