NITRATION OF NITROBENZENE IN FENTON?S PROCESSES

LUCIANO CARLOS; DANIELA NICHELA; JUAN M. TRISZCZ; JUAN I. FELICE; FERNANDO S. GARCÍA EINSCHLAG

CHEMOSPHERE

PERGAMON-ELSEVIER SCIENCE LTD

Año: 2010 vol. 80 p. 340 - 345

0045-6535

Previous studies of nitrobenzene (NB) degradation by Fenton and photo-Fenton technologies have demonstrated the formation and accumulation of 1,3-dinitrobenzene (1,3-DNB) as a highly toxic reaction intermediate. In the present study, we analyze the conditions that favor 1,3-DNB formation during NB degradation by Fe+2/H2O2, Fe+3/H2O2, UV/Fe+3/H2O2  or UV/H2O2 processes. Nitration yields in Fenton, Fenton-like and photo-Fenton techniques were much higher than those observed in UV/H2O2  systems. Besides, several tests showed that 1,3-DNB formation increases with the initial iron concentration, and decreases as the initial H2O2 concentration increases.In order to asses the key species involved in NB nitration mechanisms, additional experiments were performed in the presence of NO2- or NO3-. In dark systems, 1,3-DNB yield significantly increased with increasing [NO2-]0, while it was not affected by the presence of NO3-. In contrast, 1,3-DNB yields were higher and more strongly affected by the additive concentration in UV/NO3- systems than in UV/HNO2/NO2-systems. The addition of 2-propanol in irradiated systems markedly decreased 1,3-DNB production, thereby suggesting that NB molecule does not react with the nitrating agents ONOOH, ?NO or ?NO2. The results suggest that, in the experimental domain tested, the prevailing NB nitration pathway involves the reaction between the ?OH-NB adduct and ?NO2 radicals.