Evaluation of the Efficiency of Photodegradation of Nitroaromatics Applying the UV/H2O2 Technique
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- 作者：Fernando S. Garcí ; a Einschlag ; Jorge Lopez ; Luciano Carlos ; Alberto L. Capparelli ; André ; M. Braun ; and Esther Oliveros
- 刊名：Environmental Science & Technology
- 出版年：2002
- 出版时间：September 15, 2002
- 年：2002
- 卷：36
- 期：18
- 页码：3936 - 3944
- 全文大小：242K
- 年卷期：v.36,no.18(September 15, 2002)
- ISSN：1520-5851
文摘
Photolysis of nitroaromatic compounds in aqueoussolution is a very slow and inefficient process. As alreadyobserved for a variety of organic pollutants, considerablyfaster degradation rates of nitrobenzene (NBE), 1-chloro-2,4-dinitrobenzene (CDNB), 2,4-dinitrophenol (DNP), and4-nitrophenol (PNP) could be achieved, when the oxidativedegradation of these compounds was initiated by hydroxylradicals produced by UV-C photolysis of H2O2. Analysisof intermediate products formed during irradiation by HPLCand IC showed that cleavage of the aromatic ringshould occur at an early stage of the oxidation processand that organic nitrogen was almost completely convertedto nitrate. The optimal initial concentration of hydrogenperoxide ([H2O2]OPT) leading to the fastest oxidation rate,which depends on the initial substrate concentration ([S]0),could be evaluated using a simplified expression basedon the main reactions involved in the first stages of thedegradation process. Using only a minimum of kinetic andanalytical information, this expression shows that theratio ROPT (= [H2O2]OPT/[S]0) is related to the bimolecularrate constants for the reactions of hydroxyl radicals withsubstrate (kS) and H2O2 (kHP) and to the corresponding molarabsorption coefficients (
S, HP). Competition experimentsbetween selected pairs of the substrates showed that theirrelative reactivity toward hydroxyl radicals could becorrectly predicted using the same simplified approach.The results of our investigations as well as literature datasupport the general validity of the proposed procedurefor optimizing oxidation rates of the UV/H2O2 process.
S, HP). Competition experimentsbetween selected pairs of the substrates showed that theirrelative reactivity toward hydroxyl radicals could becorrectly predicted using the same simplified approach.The results of our investigations as well as literature datasupport the general validity of the proposed procedurefor optimizing oxidation rates of the UV/H2O2 process.