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Nano-titanium dioxide photocatalytic degradation of organic matter

2014-01-24 by seoer8

The main one is the water of organic pollutants . It is many kinds of toxicity . EPA published 129 kinds of basic contaminants , many organic pollutants studied, the results showed that : In addition , nitrobenzene, carbon tetrachloride , trichlorethylene slow degradation , other materials can be degraded rapidly . The final product is an inorganic substance such as HCl and CO2 . Currently , there may be a titanium dioxide range of major organic pollutants in water have been tried with nano-titanium dioxide decomposition Photocatalytic Oxidation , these experimental results show that the nano-titanium dioxide photocatalytic degradation of organic pollutants in the field of good governance organic matter in water applications.
( A ) they consider the photocatalytic oxidation of aliphatic hydrocarbons is gradually oxidized to the corresponding alcohols , aldehydes, hydroxy acid intermediate , and then through the Kolbe reaction of hydroxy acid is decomposed into lower hydrocarbons and H2 and CO2. Aromatics can also be TiO2 photocatalytic oxidation to CO2, but there will be a small amount of intermediate generation, such as catechol, hydroquinone , and muconic acid and other phenols . Okamoto , etc. By tracking analysis during the reaction of phenol original , intermediates and products observed reaction into three stages: the first stage mainly benzene hydroxy compound , which is detected between hydroquinone , o hydroquinone, pyrogallol 2 - hydroxy-1 ,4 - benzoquinone , 1,4 - benzoquinone. The second phase of polar hydroxy acids and aldehydes , mainly in about ten minutes after the complete removal of phenol , aromatic hydroxy compounds are also disappearing . The third stage is gradually increased CO2 production , three hours after the reaction , 80% conversion of phenol to CO2. Phenol can be inferred photocatalytic degradation reactions , mainly through hydroxylation process completed . First with phenol hydroxyl radical reaction of the dihydroxy cyclohexadiene radicals further oxidized quinone dehydration and finally degraded to CO2.
( 2 ) halogenated organic compounds are widely distributed range of halogenated organic compounds in water , a class of toxic pollutants. 114 kinds of basic pollutants listed in the U.S. Environmental Protection Agency , more than 50% of such contaminants . Such materials include the halogenated aliphatic hydrocarbons , halogenated aromatic hydrocarbons, halogenated fatty acids , used as pesticides, insecticides and the like. Priority hazardous substances controlled by countries such substances in the " blacklist" occupies a large proportion. Therefore, the study of halogenated organics management is an important issue of water pollution treatment . Photocatalytic technology in the treatment of organic halide display a good prospect that the current research in this regard have been many reports . ① halogenated aliphatic hydrocarbons and halogenated carboxylic acids in the city water in the purification process using the commonly used method of chlorination , thereby resulting in water containing a small amount of chlorinated hydrocarbons and chlorinated carboxylic acid , such as chloroform , dichloroacetic acid and the like. 1983 , DF Ollis photocatalyst TiO2 as such by irradiation with near ultraviolet 300-400 nm, a halogenated hydrocarbon or a halogenated carboxylic acids can be substantially completely degraded into HCl and CO2.

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