Photodegradation of nitroaromatic compounds in aqueous solutions in the UV/H_2O_2 process

Article type: Research Article

Authors: CHEN, Bing | YANG, Chun | GOH, Ngoh Khang

Affiliations: Division of Chemistry, Nanyang Technological University, 1 Nanyang Walk, Singapore 637616

Note: [] Corresponding author. E-mail: [email protected]

Abstract: Photodegradation of nitrobenzene and nitrophenols in aqueous solutions by means of UV/H_2O_2 process was studied in the Rayox batch reactors. Three nitrophenol isomers were identified as main photoproducts in the irradiated NB aqueous solutions. The distribution of nitrophenol isomers follows the order p-> m-> o-nitrophenol. Other intermediates detected include nitrohydroquinone, nitrocatechol, catechol, benzoquinone, phenol, nitrate/nitrite ions, formic acid, glyoxylic acid, maleic acid, oxalic acid and some aliphatic ketones and aldehydes. The degradation of nitrobenzene and nitrophenols at initial stages follows the first-order kinetics and the decay rate constants for nitrobenzene(NB) are around 10^{-3}–10^{-2}s^{-1} and for nitrophenols are around 10^{-2}s^{-1}. The decomposition of H_2O_2 in the presence of NB and each nitrophenol isomers follows zero-order kinetics. The quantum yields at initial stages for NB decay were estimated around 0.30 to 0.36, and for NPs decay is around 0.31–0.54.

Keywords: photodegradation, nitrobenzene, nitrophenols, UV/H[TeX:] _2O[TeX:] _2 process

Journal: Journal of Environmental Sciences, vol. 17, no. 6, pp. 886-893, 2005