Photocatalytic - Ozone Technology In Environmental Engineering,

Recently, the technique of photocatalysis combined with ozone has revealed wide prospect in application for the treatment of organic wastewater and has become focuses of advanced oxidation processes.The properties of organics degradation by photocatalysis combined with ozone was studied in this article. The experimental results show that the synergic degradation by photocatalysis combined with ozone is far more efficient than either of them above, and there should be a synergic effect in the degradation of organics. The essential reason for the synergic effect is that more hydroxy radicals are formed when ozone captures the electrons in the process of photocatalysis. The kinds of organics have some influence on the synergic effect by photocatalysis combined with ozone. Especially, the synergic effect is remarkable when the organic reacts with ozone slowly. Also concentration of the organic influences the synergic effect. The synergic effect strengthens when concentration of the organic becomes higher. At the mean time, the flow rate of ozone has influence on the synergic effect. When the flow rate grows, the synergic effect is reverse. The mechanism of degradation of organics by photocatalysis combined with ozone is confirmed by the experiments.The degradation behavior of typical organics in environment by photocatalysis combined with ozone was studied in this article, too. These organics include aromatic compounds, dyes, dye intermediates, carboxylic acids, alcohols and amines.?The degradation of aromatic compounds The study of aniline degradation indicates that the initial pH value has little influence on the degradation of aniline by photocatalysis combined with ozone. Aniline can be completed degraded by the technique regardless of the concentration of aniline. The degradation effect is better and the degradation time is shorten with the growth of the ozone flow. However, when the ozone flow increases to some degree, the degradation efficiency is not obvious any more. The degradation of nitrobenzene has the same condition with that of aniline. And in the process of nitrobenzene degradation, GC-MS found the main intermediates, which include 2-nitrophenol, 3-nitrophenol, 4-nitrophenol, 1,3-nitrobenzene or 1,4-nitrobenzene and Azobenzene. In addition, the influence of structures of aromatic compounds on efficiency of photocatalysis combined with ozone was also studied, which indicates that the properties and positions of substitutive radicals have some influence on the degradation reactivity.㏕he degradation of dyes and dye intermediates The pretreatment of bromamine acid of middle-level COD value or lower and dye intermediate H-acid were conducted by photocatalysis combined with ozone. The experimental resultsAbstractindicate that after short time of catalytic degradation of bromamine acid, the decolorization efficiency reaches over 70% and the value of COD is decreased at certain degree. At the same time, the value of BOD5/COD increases from 3.0%-4.3% to 32.0%-36.8%, which means that biodegradability of the wastewater is largely raised. After 4h oxidation of H-acid, the COD value of H-acid decreases from 920mg/L to 230mg/L, and the value of BOD5/COD increases from 0.014 to 0.26, and the biodegradability of wastewater is improved obviously, too. The experiment results of decolorization of 17 kinds of soluble dye solution indicate that the technique of photocatalysis combined with ozone has strong ability of decolorization. Also there is a quite close relationship between decolorization efficiency and dye structure. The length of dye conjugated chain, electron density, existence of hydrogen bond formation of nitrogen atom in the azo double bond with near group, and the level of negative electricity of substitutive radical can influence the decolorization.(3)The technique was also applied to the degradation of carboxylic acids, alcohols and amines which provide a large number of useful data for theory research and practical application.The technique is used to treat industrial wastewater, suc...