【作者】 赵彬侠；

【导师】 金奇庭；

【作者基本信息】 西安建筑科技大学 ， 环境工程， 2007， 博士

【摘要】 吡虫啉以其高效、低毒、低残留的特点，成为新一代农药的代表，其生产废水中含有大量丙烯腈、甲苯、DMF及少量的2-氯-5-氯甲基吡啶等，属于典型的高浓度难降解毒性有机废水，直接排放会严重污染环境。采用传统的生物或物化工艺处理该废水效率低、效果差，因而，成为困扰农药企业的一项环保难题。本文以吡虫啉农药生产废水为研究对象，采用湿式氧化技术进行污染物降解反应的基础及应用研究，为该工业废水处理提供理论和工艺依据。在2L高温高压间歇式反应釜中考察了湿式空气氧化工艺（WAO）处理吡虫啉废水中主要操作条件对处理效果的影响，发现在所考察的反应温度、供氧量、进水浓度、搅拌强度和进水pH等诸多因素中，温度是影响WAO效率的关键因素。供氧不足时氧化反应受到明显限制，而氧分压高于理论需氧量时，氧对处理效果影响不显著。进水pH对WAO处理吡虫啉农药废水影响较小。供氧量充足条件下，WAO在较宽污染物浓度范围内具有良好的处理效果，最大COD去除率达62％。以H₂O₂为氧化剂替代气态氧开发了湿式过氧化氢氧化工艺（WPO），研究表明，WPO处理效果受温度、pH和H₂O₂用量影响，在130℃、总压0.6 MPa、反应55min条件下，能取得相当WAO 210℃、总压8 MPa、反应120min下的60％的COD去除率。催化湿式空气氧化工艺（CWAO）能在较温和条件下提高处理效果。实验显示，使用均相催化剂可大大改善COD去除率，铜盐的催化性能优于铁盐和铈盐，而铜盐中硝酸铜则优于硫酸铜。使用硝酸铜作催化剂时，反应30 min COD去除率可达97.5％。固体催化剂较之均相催化剂能避免重金属二次污染产生。本文采用共沉淀法制备了Cu／Mn、Cu／Ni、Mn／Ce复合氧化物固体催化剂，以CWAO处理吡虫啉农药废水检测催化剂活性，研究并优选了催化剂制备工艺条件，如沉淀剂种类、沉淀物沉淀温度、干燥和焙烧温度及时间、活性组分配比等。焙烧温度及活性组分配比是影响催化剂活性的主要因素；催化剂最优制备条件为：沉淀剂NaOH，沉淀温度80℃，干燥条件110℃12h；焙烧时间8h，对Cu／Mn催化剂，焙烧温度800℃，Cu-Mn比1：2：对Cu／Ni催化剂焙烧温度700℃，Cu-Ni比2：1；对Mn／Ce催化剂焙烧温度300℃，Mn-Ce比为7：3。XRD分析表明，三系列催化剂中都有固溶体的形成，这提高了催化剂的活性和稳定性。重点研究了Mn／Ce催化剂活性组分配比与活性的关系，在催化剂表面Ce以Ce⁴⁺存在，而Mn有多种价态，Mn的氧化价态随组成的变化而变化，催化剂的活性位点归于呈高氧化态的Mn氧化物；分析催化机理证实Mn／Ce复合氧化物催化剂具有较高的催化活性。以Mn／Ce为催化剂研究了CWAO处理吡虫啉农药废水的操作参数，如反应温度、氧分压、进水pH对催化剂活性及稳定性的影响，确定了最优工艺条件，即温度190℃、总压4.8MPa、氧分压为1.6 MPa、pH 6.21，反应时间120min；COD去除率达93.1％，废水BOD₅／COD由0.19提高到0.65以上，Mn、Ce的溶出量最小，分别为0.0299 mg／L、0.0316 mg／L。采用浸渍法制备了Cu-Ni-Ce／SiO₂催化活性良好的负载型催化剂，通过CWPO评价并优化了制备工艺。综合考虑活性和稳定性，优化的制备条件为：总负载量4％，Ce添加量0.16％，焙烧温度700℃。以10g／LCu-Ni-Ce／SiO₂催化剂加入量，进行CWPO处理吡虫啉农药废水，在温度110℃、pH 7.0、总压0.6 Mpa、反应时间60 min下，COD去除率达89.1％，与CWAO相比反应条件大为缓和。以多种表征方法对不同焙烧温度和不同Ce添加量的Cu-Ni-Ce／SiO₂催化剂结构进行了分析表征，探讨了适量添加Ce提高催化剂活性机理。SEM分析证明，Ce的添加促进了催化剂表面Cu-Ni的分散性；BET测定证明，Ce添加量为0.16％时，Cu-Ni-Ce／SiO₂比表面积最大；XRD测定了催化剂的晶相结构，Cu以CuO物种存在，同时监测到铜镍复合氧化物的衍射峰；XPS分析了催化剂表面元素Cu、Ni、Ce、O的化学态，证明催化剂表面存在三种状态的氧，即晶格氧、羟基氧和吸附氧，测定了不同化学态氧的含量。降低焙烧温度并适量添加Ce都能增加吸附氧占总氧的比例，促进氧在催化剂表面的吸附，从而形成强氧化物种O₂^-，这有利于催化剂活性的提高。论文对湿式氧化处理吡虫啉农药废水的动力学进行了探讨，建立了一级两阶段动力学模型，较好地解释、关联了WAO、WPO、CWAO、CWPO四种工艺的实验数据。得出了四种工艺每个反应阶段的反应速率常数k及表观活化能E_a，为湿式氧化处理吡虫啉农药废水工艺放大设计提供了理论依据。更多还原

【Abstract】 Imidacloprid becomes a typical representative of the new generation pesticide with higher efficiency, lower toxicity and residue. Liquid effluents from imidacloprid production containing high acrylonitrile, toluene and DMF concentrations are difficult of degradation organic wastewater. It will pollute the environment seriously if discharged directly. However, the conventional processes, such as biological systems are inefficient. By taking the actual-producing wastewater of imidacloprid pesticide as the subject, study on base and application of organic contamination degradation were carried out by wet oxidation technology roundly in this paper in order to solve the problem for enterprise and to provide a effective way for the treatment of high concentrated wastewater.Oxidation experiments were conducted in a 2L autoclave which can withstand high temperature and high pressure. The various factors, such as reaction temperature, oxygen partial pressure, concentration and pH influent, intensity of stir on the wastewater treatment efficiency were investigated. The reaction temperature was a key factor of influence on the efficiency of the WAO. Oxidation reaction was limited notably when oxygen was insufficient, but as oxygen partial pressure exceeded to a certain value, treatment efficiencies were less significant. The influence of the pH in influent on the WAO was relatively small. As long as the amount of oxygen is enough, WAO still had a good processing effect within the range of wider concentration in influent.Wet peroxide oxidation （WPO） which totally used hydrogen peroxide as oxidant was developed. The results showed that the efficiency of WPO was influenced by temperature, pH and dosage of hydrogen peroxide. WPO was found to attain the same COD removal efficiency 60% as compared to WAO but with the reaction temperature lowered from 210℃to 130℃, and the total pressure from 8MPa to 0.6MPa.The homogeneous catalyst can improve the COD removal efficiency greatly. Among all the homogeneous catalysts tested, copper salt was found to be more effective in treatment of imidacloprid production wastewater. Cupric nitrates were more active than the copper sulfates. While using cupric nitrate as the catalyst, the COD removal efficiency was reached to 97.5% after reacting 30 min.The complex oxide catalysts of Cu/Mn, Cu/Ni, Mn/Ce were prepared by the co-precipitation method and applied to the treatment of pesticide wastewater of imidacloprid production by catalytic wet air oxidation. The preparation processes including the types of precipitator, aging temperature of precipitator, the drying temperature, the calcination temperature and time, active component proportion conditions which might effect on the activity of the bi-metal catalysts, were optimized. Among all preparation conditions, calcination temperature and active component composition were more important influences on catalytic activity than others, and results were as follows. NaOH was the precipitator, aging temperature was 80℃, drying temperature was 110℃for 12h, calcination time was 8h. For Cu/Mn catalyst, calcination temperature was 800℃and the Cu/Mn molar ratio was 1:2; For Cu/Ni catalyst, calcination temperature was 700℃and Cu/Ni was 2:1; For Mn/Ce catalyst, calcination temperature was 300℃and Mn/Ce was 7:3.XRD data revealed that the ’solid solutions’ were formed in all the three series catalysts that improved greatly activity and stability of the catalysts. Mn/Ce composition-activity relationship was investigated mainly. XPS analysis indicated that Ce existed of Ce⁴⁺ on the surface of catalyst, and Mn had several oxide phases, which varies with the composition of Mn/Ce. Catalytic active sites have been ascribed to manganese oxide species exhibiting higher oxidation state. The analysis of catalytic mechanism showed that Mn/Ce complex oxide catalyst had higher catalytic activity. The effect of operation parameters of CWAO including reaction temperatures, oxygen partial pressure and pH value of wastewater on the activity and stability of Cu/Mn catalyst were studied, and the optimum condition of CWAO was confirmed, which was temperature of 190℃, oxygen partial pressure of 1.6MPa, total pressure 4.8MPa, pH of 6.21. Using Mn/Ce catalyst, 93.1% COD removal was obtained in CWAO of wastewater from imidacloprid production after 120min under the optimized reaction conditions. BOD₅/COD of the wastewater increased from 0.19 to more man 0.65, the concentration of leached Mn and Ce were 0.0299mg/L and 0.0316mg/L, respectively.A type of CWPO catalysts, Cu-Ni-Ce/SiO₂ prepared by the impregnation method was found to have high catalytic activity. The preparation process were optimized by CWPO, considering the activity and stability synthetically, the optimum conditions were total loading amount of 4%, 0.16% of Ce content and calcination temperature of 700℃. CWPO process was carried out with 5g Cu-Ni-Ce/SiO₂ catalyst to deal with the imidacloprid wastewater under 110℃, pH =7.0, total pressure of 0.6Mpa which were gentler greatly than that of CWAO process, 89.1 %COD removal was obtained after 60min.All catalysts of Cu-Ni-Ce/SiO₂ prepared under different calcination temperature and Ce content were characterized by XPS, XRD, SEM and nitrogen adsorption techniques. It was discussed that the mechanism of that adding certain amount of Ce improved the catalyst activity. SEM image revealed that addition of Ce promoted the dispersion of Ni and Ce particles on the surface of catalyst It was proved by BET that the surface area of Cu-Ni-Ce/SiO₂ was the largest when the Ce content was 0.16%. The catalyst structure was analyzed by XRD. CuO and complex oxide were observed on the catalyst surface. XPS was used to analyze the composition and the chemical state of the catalyst surface elements of Cu, Ni, Ce and O. Moreover the percentage of the three kinds oxygen, the lattice oxygen, hydroxy oxygen and chemisorbed oxygen, to total oxygen was obtained. The amounts of chemisorbed oxygen were increased on the surface of Cu-Ni-Ce/SiO₂ catalysts with decreasing calcination temperature and adding feasible Ce content, and the oxygen absorbing on the catalyst surface was promoted. Therefore, the oxygen reactive specie O₂^- was produced. This was favorable to improve the catalyst activity.The reaction dynamics for wet oxidation of imidacloprid wastewater in four react systems which were WAO, CWAO （added with Mn/Ce catalyst）, WPO, CWPO （added with Cu-Ni-Ce/SiO₂ catalyst） were studied in the batch slurry reactor. The rate of chemical oxygen demand （COD） reduction was described by two steps first-order kinetics. The specific react rate coefficient and activation energies were determined for WAO, WPO, CWAO and CWPO, respectively. The kinetic model was found to agree well with experimental results. It is useful for the application of wet oxidation in industrial wastewater treatment更多还原