Influence of nitrite on the degradation of halogenated phenols in sulfate radical oxidation processes
The influence of nitrite(NO2)on the degradation of bromophenol and chlorophenol by sulfate radical(SO4·-)oxidation was systematically investigated in this work.Results showed that the presence ofNO2 accelerated the degradation of bromophenol,while posed a weak effect on the degradation of chlorophenol.Meanwhile,NO2 led to a series of toxic nitrated byproducts.Upon SO4·-oxidation,halophenols underwent dehalogenation and the released halides can be further oxidized by SO4·-to form reactive halogen species,which rapidly react with some intermediates and the parent compounds to form halogenated byproducts,such as haloform and haloacetic acid.Once NO2-was co-present,these reactive halogen species can be scavenged by NO2-to form a strong oxidizing agent,nitryl halide.Then nitryl halide reacts with the parent halophenol,promoting their degradation and resulting in the formation of nitrated byproducts.Besides,NO2 can be oxidized to nitrogen dioxide radicals(NO2·)by SO4·-,which further couple with phenoxy radicals generated from the oxidation of halophenols by SO4·-,yielding nitrated byproducts as well.Note that,the formation of nitrated byproducts from bromophenol(9.2 μmol/L)was significantly higher than those generated from chlorophenol(5.7μmol/L)with 200 μmol/L NO2 present.In SO4·-oxidation process,bromophenol is more prone to dehalogenation than chlorophenol.Therefore,the influence of NO2 on the transformation of bromophenol was more drastic than that of chlorophenol by SO4·-.These findings reveal potential risks of the application of SO4·-oxidation technologies for the remediation of halogenated contaminants in the subsurface environment,and provide new insights into the interaction of nitrogen and halogen in SO4·-oxidation processes.
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维普
