Degradation pathway of three chloronitrobenzenes isomers by ozone in the aqueous

The ozonation of three chloronitrobenzene isomers (p-, m-, o-chloro-nitrobenzene, CNB) were investigated. CNBs was effectively degraded by ozone but cloud not be mineralized completely. During the ozonation of CNBs process, the inorganic carbon, Cl^- and NO₃^- increased gradually, and chloro-(-Cl) and nitro-(-NO₂) group all turn to Cl^- and NO₃^- calculated by stoichiometry. The degradation products of CNBs mainly contained phenolic and carboxylic. In the process of pCNB degradation, -Cl and -NO₂ could be replaced by -OH, chlorophenol and nitrophenol were formed meanwhile. However, in the process of the degradation of oCNB and mCNB, neither nitrophenol nor chlorophenol was detected. The hydrogen on the phenyl of all these three CNBs could be replaced by -OH, thus nitrochlorophenol was produced, and ten different nitrochlorophenols were detected by GC/LC-MS. The reaction pathways of CNBs were oxidized by -OH similar to the tlectrophilic substitution reaction of aromatic ring, which -Cl and -NO₂ group or -H of phenyl ring are replaced to form free radical intermediate of cyclohexadien, and they were oxidized to hydroxybenzene group which get to lose -Cl, -NO₂ or -H forming phenols or polyhydroxy phenols. Then opened the ring or the phenyl directly opened to form low molecule carboxylic acid and CO₂.