【作者】 张占梅；

【导师】 郑怀礼；

【作者基本信息】 重庆大学 ， 市政工程， 2009， 博士

【摘要】 染料合成过程中排放的废水成分复杂,浓度高、色度大、难生物降解物质多,且含有多种具有生物毒性或三致性能(致癌、致畸、致突变)的有机物。此外,由于染料生产品种逐渐增多,并且逐步向抗氧化、抗光解、抗生化方向发展,使得染料废水处理的难度加大。未经严格处理的染料废水不但造成受纳水体的严重污染,而且给人体及生态环境也造成潜在的危害。针对染料废水化学结构稳定,对微生物有毒害的特点,常规的物化法和生化法无法取得理想的处理效果,有必要开发针对这类废水治理行之有效的处理新工艺,来满足越来越严格的环保排放标准,达到综合治理的目的。超声波降解技术是近年来水污染控制领域一个研究热点,它集高温热解、自由基氧化和超临界水氧化于一身,降解条件温和、适用范围广、操作简单。超声波技术可以单独使用,也可以与其它技术联合使用,是一种很有发展潜力和应用前景的技术。论文以偶氮染料酸性绿B为研究对象,在单因素试验设计、正交试验设计、Plackett-Burman试验设计、Box-Behnken设计和中心组合设计等试验设计的基础上,并结合响应面分析,研究了超声及超声组合技术对酸性绿B的降解效果、试验条件优化、反应过程动力学及降解机理。旨在探索偶氮染料废水降解的新途径,拓宽超声化学在水处理领域的应用范围,从而为丰富、深化超声氧化技术理论研究提供一定的数据和基础。论文的主要研究结论如下:(1)单独超声辐射降解酸性绿B,试验结果表明,单独超声处理酸性绿B效果并不理想。在优化试验条件下,酸性绿B的脱色率仅为41.8%。酸性绿B在单独超声辐射下,其降解效果受多种因素的影响,其中超声频率和功率密度是影响酸性绿B降解效果的两个重要因素。酸性绿B降解率随功率密度的增大而增大,而当超声频率由28 kHz增大为45 kHz时,降解率反而降低。此外,废水浓度、初始pH值、饱和气体和无机盐溶液对酸性绿B降解也有一定的影响。在反应体系中投加自由基清除剂,降解效果大大降低,说明酸性绿B超声降解反应以自由基氧化为主。通过分析降解前后的紫外-可见光谱图,初步推断在超声辐射下,酸性绿B并没有完全降解为CO2和H2O,而仅仅是生色基团受到自由基攻击而被破坏。反应过程符合表观一级反应动力学。(2)在双频超声降解酸性绿B的试验中,研究发现,在给定试验条件下,双频超声波对酸性绿B的降解效果优于两种单频超声波的脱色效果之和,双频超声存在一定的协同效应。在优化试验条件下,即在28 kHz+40 kHz组合的双频超声复合模式下,调节废水pH = 4.0,控制超声输入功率为490 W,反应时间为165 min,废水浓度为100 mg/L时,酸性绿B脱色率为64.6%。通过对双频超声系统中?OH产额的测定和分析空化泡的Rayleigh-Plesset运动方程,初步探讨了双频超声协同效应产生的原因和机理。(3)在超声-H2O2降解酸性绿B的试验中,以酸性绿B脱色率为目标响应值,采用响应面法中的Box-Behnken设计建立酸性绿B降解反应的数学模型。在模型确定的优化试验条件下,酸性绿B降解率的理论预测值为96.82%,而验证试验表明酸性绿B的实际脱色率为93.34%,试验值与模型预测值偏差仅为3.48%,表明该模型具有高度显著性,回归模型预测值与实验值拟合性好,可用该模型对酸性绿B降解反应进行预测。由响应面及等高线图分析,染料初始pH值、H2O2投加量、超声功率三因素对酸性绿B降解的影响不是简单的线性关系,两两间亦有一定的交互作用。此外,研究发现,在反应体系中加入自由基清除剂正丁醇对酸性绿B的降解有明显的抑制作用,且反应体系中?OH自由基浓度与酸性绿B脱色率成正比例关系,说明酸性绿B在超声-H2O2体系中的主要降解途径是通过?OH自由基使酸性绿B氧化的过程。反应遵循表观一级反应动力学规律。(4)在超声-Fenton降解酸性绿B的试验中,为获得超声-Fenton降解酸性绿B的优化试验条件,设计5因素3水平的L27(35)正交试验。结果表明:因素对酸性绿B脱色反应影响的大小次序为:pH>反应时间>Fe2+投加量>功率密度>H2O2投加量>交互作用。酸性绿B脱色反应的优化工艺为:Fe2+投加量为7 mmol/L;H2O2投加量为140mmol/L;废水pH值为3.5;功率密度为1.00 W/mL;反应时间为30 min。而对酸性绿B的COD去除率影响的大小次序为:反应时间> H2O2投加量>pH>Fe2+投加量>功率密度>交互作用。酸性绿B的COD去除反应的优化工艺:Fe2+投加量为6 mmol/L;H2O2投加量为120mmol/L;废水pH值为4.0,功率密度为1.00 W/mL;反应时间为40 min。酸性绿B在超声-Fenton体系中的降解反应主要是基于羟基自由基的氧化反应为主,酸性绿B在羟基自由基的攻击下,首先生成苯和萘的衍生物,而随着反应的继续进行进一步为降解为小分子中间体。(5)以Al2O3为载体制备Fe-Ni-Mn/Al2O3催化剂,并对催化剂的性能进行表征。采用正交试验设计考察负载溶液浓度、负载时间和焙烧温度对催化剂性能的影响。试验结果表明,当负载溶液浓度、负载时间和焙烧温度分别为0.1mol/L,12 h和550℃时,催化剂的活性最好。以Fe-Ni-Mn/Al2O3为催化剂、H2O2为氧化剂,考察超声催化氧化酸性绿B的降解效果。首先采用Plackett-Burman设计对影响酸性绿B降解反应的8个因素,即催化剂投加量、催化剂使用次数、H2O2投加量、反应时间、废水初始浓度、废水pH值、超声功率和超声频率,外加三个虚拟变量,进行初步筛选。然后根据中心组合设计对Plackett-Burman筛选出的三个主要因素:催化剂投加量、H2O2投加量、溶液pH值进行响应面优化设计,从而得到酸性绿B催化氧化反应的优化条件。试验得到酸性绿B的脱色率平均值为96.76%,而由回归模型预测的酸性绿B的脱色率为94.11%,预测值和试验值较接近,偏差仅为2.65%,说明试验值与预测值之间拟合性良好,证明用此模型对超声降解染料酸性绿B优化实验条件进行分析和预测准确可靠,预测结果充分、可信,具有一定实用价值。由降解反应后酸性绿B的紫外-可见光谱图、离子色谱图和GC-MS扫描图知酸性绿B已被完全降解,并对酸性绿B的反应历程进行了推断。研究认为,酸性绿B在Fe-Ni-Mn/Al2O3催化剂存在下超声降解反应机理是超声效应使催化剂Fe-Ni-Mn/Al2O3表面得到不断的摩擦、清洗和更新,不仅使得催化剂有效表面积增加,可保持较多的催化活性位,而且可加速酸性绿B分子在催化剂表明的物质传输,强化降解效果。更多还原

【Abstract】 Dye wastewater from dye synthesis process has characteristics of complex constituents, high concentration and high colority. Moreover, it contains many biorefractory compounds and carcinogenic or teratogenic organic matters. With the increase of the variety of dye, the dye wastewater is becoming more difficult to treat since dyes are designed to be resistant to chemical oxidation, photochemical degradation and biodegradation. If the dye wastewater cannot be processed properly, they will not only pollute seriously the receiving water but also have the potential danger to the public health and ecologicalenvironment. Generally, azo dyes have the stable chemical structure and they are toxic to microorganism, as a result, the common physicochemical processes and biochemical processes can not achieve the sastisfactory results. In order to follow the environmental standard and achieve the purpose of comprehension treatment, it is necessary to develop a new and effective process aiming at treating this kind of dye wastewater. The ultrasound irradiation technology has been a study focus in the water pollution control field in recent years. It has the characteritis of the advanced oxidation processes including thermolysis, radical oxidation and supercritical oxidation. The ultrasound irradiation technology can be operated under the mild condition and the reaction is rapid. In addition, it can be applied alone or with other treatment technologies, so the ultrasound irradiation is considered a potential and promising technology.In this dissertation, azo dye Acid Green B was choosed as the model contaminant. Based on single parameter design, orthogonal design, Plackett-Burman design, Box-Behnken design and central composite design and response surface method, the degradation efficiency, the optimal experimental conditions, reaction kinetics and degradation mechanism of Acid Green B by ultrasound irradiation and ultrasound in combination with other treatment methods were investigated in detail. The purpose of this study is to expand the application range of sonochemistry in the field of wastewater treatment and to explore the new method to degrade the azo dye wastewater. At the same time, this study will provide experimental data for azo dye wastewater treatment and fundamental theory for the mechanism study of sonochemistry. Main results in this dissertation are summarized as follows:(1) In the case of degradation of Acid Green B by the single frequency ultrasonic irradiation, the experimental results showed that the degradation efficiency of Acid Green B was not satisfactory. The decolourity ratio of Acid Green B was just 41.8% under the optimal experimental conditions. The degradation efficieny was influenced by many factores, especially ultrasonic frequency and power density. the degradation efficiency of Acid Green B increased with the increase of power density, but it decreased when the ultrasonic frequency changed from 28 kHz to 45 kHz. In addition, the degradation efficiency was affected by Acid Green B concentration, initial pH value, bubbling gas and inorganic salts. The degradation efficiency of Acid Green B reduced greatly when the radical scavenger was added into the reaction system, which indicated the degradation of Acid Green B was achieved mainly through the radical oxidation reaction. The UV-Vis spectra of Acid Green B before and after degradation were analyzed and the following conclusions cound be drawn: Acid Green B was not completely mineralized to CO2 and H2O by the single frequency ultrasonic irradiation, instead, the chromophore in Acid Green B molecular structure was just destroyed under the attack of radicals. The degradation reaction of Acid Green B by single ultrasonic irradiation followed the first-order kinetics reaction.(2) In the case of degradation of Acid Green B by dual-frequency ultrasonic irradiation, the results showed that the degradation efficiency of Acid Green B by dual frequency ultrasound irradiation was proved to be superior to the total value of two single frequency ultrasound irradiation at the given experimental conditions, which indicated there was the synergistic effect in the dual frequency ultrasonic irradiation system. The decolouration ratio of 64.6% could be achieved when pH value was 4.0, input power was 490 W, the reaction time is 165 min and the initial concentration of dye wastewater is 100 mg/L. The detailed reasons and machanisms of the synergistic effect in the dual frequency ultrasonic irradiation system were studied on the base of the measurement of the quantity relationship of ?OH and analyzing the Rayleigh-Plesset equation of. the wall of cavitation bubbles.(3) In the case of degradation of Acid Green B by ultrasonic irradiation and H2O2. The decolourity ratio of Acid Green B was the objective response value, and the response surface methodology based on Box-Behnken design was employed to build the predictive mathematical model of Acid Green B degradation reaction. Under the optimum experimental conditions obtained by the predictive model, the predictive value of Acid Green B decolourity ratio is 96.82% according to the predictive model. The adequacy of the model equation for predicting the optimum response values was verified under the same experimental conditions and the experimental value is 93.34%, which was fitted to the predicted value by polynomial quadratic model with the deviation of just 3.48%. The confirmatory test showed that the predictive model has a significant difference and the experimental values agreed with the predicted values by the model. So the model can be used to the degradation reaction of Acid Green B. The response surface and contour plot was analyzed and the result showed that three factors: pH value, H2O2 dosage and ultrasonic power, were not linear relation, there is interaction reaction among these factors. The radical scavenger n-butanol was proved to inhibit the degradation reaction of Acid Green B. Moreover, there is proportional relationship between ?OH concentration and Acid Green B degration efficiency. So it can be drawn that the main degradation mechanism of Acid Green B was radical oxidation ?OH, and the reaction followed the apparent first-order kinetics reaction.(4) In the case of degradation of Acid Green B by ultrasonic irradiation and Fenton reaction, an orthogonal design L27(35) including 5 factors with 3 levels was applied in order to obtain the optimal experimental condtions of Acid Green B degradation by ultrasonic irradiation in combination with Fenton reation. The results showed that the effects order of 5 factors on decolourity were pH >reaction time > Fe2+ dosage > power density > H2O2 dosage > interaction effect of Fe2+ and H2O2. The optimal experimental conditions of Acid Green B decolouration reaction were as followed: Fe2+ dosage 7 mmol/L, H2O2 dosage 140mmol/L, pH value 3.5, power density 1.00 W/mL and reaction time 30 min. The effects orders of 5 factors on COD removal were reaction time> H2O2 dosage > pH > Fe2+ dosage > power density > interaction effect of Fe2+ and H2O2. The optimal experimental conditions of Acid Green B COD removal reaction were as followed: Fe2+ dosage 6 mmol/L, H2O2 dosage 120mmol/L, pH value 4.0, power density 1.00 W/mL and reaction time 40 min. The degradation mechanism is mainly radical oxidation of ?OH. The degradation path of Acid Green B by ultrasonic irradiation and Fenton reaction was explored. Firstly,. Acid Green was degraded into derivatives of benzene and naphthalene under the attack of ?OH, and then some small molecular organic intermediates were produced.(5) Fe-Ni-Mn/Al2O3 catalyst was prepared using Al2O3 as the carrier and the properties of Fe-Ni-Mn/Al2O3 catalyst were characterized. The effects of loaded solution concentration, loaded time and roast temperature on catalyst property were investigated by using an orthogonal experimental design. The experimental results showed that the best catalytic activity was obtained when loaded solution concentration, loaded time and roast temperature were 0.1mol/L,12 h and 550℃, respectively. The degradation efficiency of Acid Green B by ultrasonic irradiation was explored in the presence of catalyst Fe-Ni-Mn/Al2O3 and the oxidizer H2O2. The Plackett-Burman design was applied to study the effects of eight variables including catalyst dosage, the used times of catalyst, H2O2 dosage, reaction time, initial concentration and pH value of Acid Green B, power density and ultrasonic frequency and three pseudo variables. The Plackett-Burman design results gave three most important variables for Acid Green B degradation including catalyst dosage, H2O2 dosge and pH value. Then, the response surface methodology based on central composite disign was used to optimize the experimental conditions of Acid Green B degradation. UV-Vis spectra、ion chromatogram and GC-MS before and after reaction showed that Acid Green B had been completely decomposed, and the degradation path of Acid Green B was also inferred. It is deduced that the degradation mechanism of Acid Green B: The surface of Fe-Ni-Mn/Al2O3 catalyst was rubbed, rinsed and refreshed under the ultrasonic irradiation, as a result, the superficial area and the catalytic spot increased on the surface of Fe-Ni-Mn/Al2O3 catalyst, moreover, the mechanical effect of ultrasonic irradiation could speed up the transmitance of Acid Green B on the surface of catalyst and enhance the reaction efficiency.更多还原