Photochemical oxidation of o-dichlorobenzene in aqueous solution by hydroxyl radicals from nitrous acid

The mechanism and kinetic parameters of the photochemical reaction of o-dichlorobenzene (o-DCB) in the presence of nitrite were studied by steady-state irradiation and laser flash photolysis. The degradation efficiency of o-DCB was observed to be influenced by N(III) (H2ONO+, HONO, NO2-) concentration, initial concentration of o-DCB and pH value. The hydroxyl radicals generated by the photolysis of N(III) attacked the benzene ring of o-DCB to form an o-DCB-OH adduct with the second-order reaction rate constant of (2.69 +/- 0.3) x 10(9) L mol(-1) s(-1). Subsequently, the o-DCB-OH adduct reacts with molecular oxygen, (NO2)-N-center dot, H2ONO+ and HONO with rate constants of (1.28 +/- 0.3) x 10(8) L mol(-1) s(-1), (1.5 +/- 0.4) x 10(8) L mol(-1) s(-1), (1.3 +/- 0.2) x 10(7) L mol(-1) s(-1) and (1.0 +/- 0.3) x 10(7) L mol(-1) s(-1), respectively. The main products of the OH-initiated reaction of o-DCB were identified by gas chromatograph and mass spectrometer (GC-MS) to be o-chlorophenol, 2-chloro-3-nitrophenol, 1,2-dichloronitrobenzene, 2,3-dichlorophenol, 2,3-dichlom-1,4-benzoquinone and 2,3-dichloro-4-nitrophenol and the reaction mechanism leading to these products is discussed.

Automated summary

The study on the photochemical reaction of o-dichlorobenzene in the presence of nitrite revealed that the degradation efficiency is influenced by the concentration of N(III), initial concentration of o-DCB, and pH value. The hydroxyl radicals generated by the photolysis of N(III) attack the benzene ring of o-DCB to form a new compound, leading to the formation of different products.