【作者】 王群；

【导师】 马军；

【作者基本信息】 哈尔滨工业大学 ， 市政工程， 2010， 博士

【摘要】 臭氧催化氧化深度处理工艺是一种有效地分解水中高稳定性有机物的方法,它在水处理领域有很好的应用前景,影响其应用的关键因素在于高效催化剂的研制以及氧化过程中溴酸盐的生成控制问题,同时缺乏系统的设计参数(如停留时间、催化剂加入量等)以指导工程实际。研究利用催化剂强化臭氧氧化的作用机理与途径,是研制高效催化剂并将其应用于工程实际的基础。论文中选择了几种有代表性的催化剂；氧化铈、羟基氧化铁、氧化镁、氧化铝以及高硅沸石等,它们在臭氧催化氧化有机物时所遵循的作用机理有很大差别。本研究以氧化铈作为主要催化剂,从以下几方面考察不同催化剂对臭氧分解有机物和控制溴酸盐的催化氧化规律：(1)考察了不同条件下氧化铈催化臭氧氧化有机物的效能,并论证氧化铈催化臭氧氧化水中有机物的作用机理；(2)以滤后水为对象,研究不同催化剂强化臭氧氧化前后水中有机物分子量分布以及官能团的变化情况,并考察了单独臭氧氧化与催化剂联用的可能性；(3)考察了不同条件下氧化铈催化臭氧氧化控制水中溴酸盐的效能,初步探讨了氧化铈催化臭氧氧化控制水中溴酸盐生成的机理；(4)通过连续流试验,考察了不同条件下催化剂对臭氧分解的促进效能,并讨论了相同催化剂在不同条件下以及不同催化剂之间臭氧分解与催化剂强化臭氧氧化有机物之间的关系。在本研究中选择了两种比较典型的目标物—对氯硝基苯和邻苯二甲酸(PA),这两种有机物与臭氧分子的氧化速率都非常慢,对氯硝基苯通常被用作臭氧氧化过程中羟基自由基的指示性有机物,它的络合能力较差；而邻苯二甲酸具有很好的络合能力。试验过程中发现,氧化铈的存在并没有提高臭氧对水中对氯硝基苯的去除率,与单独臭氧氧化相比,对氯硝基苯的去除率反而有所降低,为了更好地研究其作用机理,通过向O3/CeO2反应体系中加入过氧化氢来激发臭氧产生羟基自由基,虽然对氯硝基苯的去除率有所提高,但仍然远小于相同条件O3/H2O2反应过程中对氯硝基苯的去除率。推断在氧化铈催化臭氧氧化对氯硝基苯的过程中,羟基自由基的产生受到了一定的抑制。氧化铈催化臭氧氧化PA时,有很好的去除效果,通过不同条件下氧化铈催化臭氧氧化PA的效果可做出如下推断：由于氧化铈表面的Ce4+是较强的Lewis酸,很容易吸附溶液中的PA和臭氧,PA与氧化铈形成Ce(Ⅳ)-PA中间体,而臭氧与氧化铈形成氧化能力比臭氧更强的表面键O·-自由基,表面键O-·自由基与PA和氧化铈形成的中间体反应,从而达到去除水中PA的目的。这个推断可以解释不同条件下氧化铈催化臭氧氧化PA时所表现出的特点,在此过程中PA在氧化铈表面上的络合吸附以及臭氧在催化剂表面的转化成为影响氧化铈催化臭氧效能的关键因素。天然水体中的有机物绝大部分是天然有机物(NOM),常规水处理工艺对NOM的去除非常有限,NOM的存在会在消毒过程中产生消毒副产物,同时使管网内细菌二次繁殖,严重影响饮用水水质。为了深入地研究不同臭氧催化氧化工艺对水中NOM的作用规律,测定了氧化过程中UV254和DOC的变化、分子量分布的变化,并用荧光技术考察了滤后水氧化前后NOM组分结构和官能团变化。O3/FeOOH氧化滤后水的矿化程度比较明显,O3/FeOOH与O3/MgO氧化滤后水的A型EEM荧光基团强度显著降低,臭氧催化氧化可以有效地降低滤后水中芳环或共轭键有机物的数量,同时将腐殖酸类物质氧化成小分子有机物。虽然O3/CeO2氧化NOM的效果较差,但是其与单独臭氧氧化联用可以显著地提高水中DOC的去除率,多种臭氧催化氧化工艺联用将是以后的发展方向。为了进一步研究CeO2控制臭氧氧化过程中BrO3的生成机理,考察了不同影响因素对CeO2控制BrO3生成的影响,同时对不同煅烧温度条件下生成的CeO2进行了表征。通过研究讨论推断,CeO2控制臭氧氧化过程中BrO3的生成主要是由于CeO2吸附了水中一些含氧负离子(如HO2、O2·等),从而抑制了羟基自由基的产生,进而控制了水中BrO3的生成。用二氧化铈催化臭氧氧化虽然不能提高对氯硝基苯的去除,但可以很好地催化臭氧氧化水中一些有机酸类物质,同时可以有效地控制溴酸盐生成。在工程应用时,二氧化铈催化臭氧氧化可以与单独臭氧氧化联用,从而进一步将单独氧化或是其它臭氧催化氧化过程中产生的有机酸类物质进一步降解,同时二氧化铈催化剂也可以在臭氧氧化或消毒过程中应用,具有很好的应用前景。更多还原

【Abstract】 Catalytic ozonation process in water treatment is an effective method for removal of stable organic pollutants, which are promising in water treatment. The key factors affecting its application are the preparation of effective catalysts and the formation of bromate during oxidation process. At the same time, there are few clear design parameters for the application guidance of catalytic ozonation (such as residence time, catalyst amount, etc).Understanding on the catalytic ozonation mechanism is the key step to develop efficient catalysts and providing sound basis for engineering applications. Some typical catalysts were selected such as cerium dioxide, hydroxy iron oxide, magnesium oxide, alumina and high silica zeolite. There are different catalytic ozonation mechanism in the presence of different types of catalysts. Cerium dioxide was selected as the major catalyst. The influence of different catalytic ozonation on the removal of organic pollutants and control bromate was discussed:1. The effectiveness and mechanism of ozone oxidation of organic pollutants with cerium oxide under different conditions were discussed; 2. The molecular weight distribution and functional group changes of organic matter after catalytic ozonation of the filtered water were investigated, the possibility of combined ozonationation alone and catalytic ozonation was also discussed;3. Bromate formation and control method in catalytic ozonation of bromide containing water in the presence of cerium oxide under different conditions were investigated, and the mechanism of bromate reduction in catalytic ozonation in the presence of cerium oxide was discussed; 4. Ozone decomposition catalysed by different catalysts was investigated and the relationship between ozone decomposition and the oxidation of organic matter in continuous flow reactor were also discussed.Two typical target-chloronitrobenzene and phthalic acid (PA) were selected in this study, which have very low oxidation rate by ozone molecules. Chloronitrobenzene with poor complexing ability were often used as indicative organic compounds of hydroxyl radical oxidation during ozonation, and PA has a good complexing ability with catalysts. The removal rate of chloronitrobenzene did not increase but decrease during catalytic ozonation in the presence of cerium oxide. In order to further study the mechanism of catalytic ozonation by cerium oxide, peroxide was added into reaction O3/CeO2 to induce hydroxyl radicals. Although the removal rate of chloronitrobenzene increased after adding cerium oxide and peroxide, it still far less than than the case achieved by O3/H2O2 under the same conditions. So it is deduced that the production of hydroxyl radicals was inhibited during the catalytic ozonation of chloronitrobenzene after adding cerium oxide.There was a good catalytic ozonation effect on PA in the presence of cerium dioxide, from which we infered that Ce(Ⅳ) of cerium oxide surface was a strong Lewis acid and it easily absorbed PA and ozone in the solution, leading to the formation of complex intermediates of PA and the formation of O·-free radicals, then O·-free radicals reacted with complex intermediates of PA. The entire reaction processes improved the removal of PA. The inference above could be used to explain the responding characteristics of catalytic ozonation of PA in the presence of cerium oxide. During entire reaction processes, the complex adsorption of PA and the conversion of ozone on the catalyst surface were the key factor of catalytic ozonation in the presence of cerium oxide.The major organic matter in natural waters was natural organic matter(NOM), which was difficult to be removed during conventional water treatment processes. The oxidation of NOM made the formation of disinfection by-products during disinfection. NOM could also cause the regrowth of bacterial in water supply networks, which seriously affect the quality of drinking water. In order to study the catalytic ozonation of NOM in water, the parameters such as UV254, DOC and SUVA changes and the structural and functional group variation of NOM illustrated by EEM of filtered water treated by catalytic ozonation were measured. The obvious mineralization of filtered water was achieved after the oxidation by O3/FeOOH, the A-EEM fluorescent intensity was significantly lower after the oxidation by O3/FeOOH and O3/MgO. Catalytic ozonation could effectively reduce the number of aromatic ring and conjugated organics in the filtered water, and oxidize humic substances into small molecular organic compounds. Although cerium oxide behave poor effective oxidation efficiency of NOM, but the use of cerium oxide in catalytic ozonation after ozone alone could significantly increase the removal of DOC. The combined process of ozonation and catalytic ozonation would be a promising process for future water treatment.To further study the mechanism of bromate reduction in catalytic ozonation by cerium oxide, the influence of different factors on bromate formation and control in catalytic ozonation was investigated and meanwhile CeO2 generated under different calcination temperatures were characterized. Based on the results of this study, and the discussion on the process of O3/CeO2 for controling the formation of BrO3-, the adsorption on CeO2 was mainly due to a number of oxygen ions in water (such as the HO2-, O2·-, etc.) on the catalyst surface, thereby inhibiting the production of hydroxyl radicals, and then control the formation of BrO3-. The mechanism of bromate reduction in catalytic ozonation in the presence of cerium oxide may be explained as follows:the adsorption of some oxygen ions(such as the HO2-, O2·-, etc.) in water which inhibited the production of hydroxyl radicals, therefore, the formation of bromate was reduced in catalytic ozonation in the presence of cerium oxide.更多还原