| 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.
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