Study on the role of hydroperoxyl radical in degradation of p-nitrophenol attacked by hydroxyl radical using photolytical technique

In order to investigate the possible role of hydroperoxyl radical (HO2) in the degradation of p-nitrophenol (p-NP) attacked by hydroxyl radical (OH), a series of experiment have been elaborately designed using UV light photolysis, pulse radiolysis and intermediate analysis. It has been demonstrated that OH is the dominant reactive oxygen specie, meanwhile both O2 and HO2 can enhance the degradation efficiency of p-NP. The accelerative effect of HO2 has firstly been distinguished from that of O2 by identifying the products in the systems of p-NP + OH, p-NP + OH + O2 and p-NP + OH + O2 + HO2. The possible reaction mechanism involved in the degradation of p-NP has been proposed, especially in the presence and absence of HO2. The ring open of phenoxy-type radical may be the key step in the accelerative effect of HO2.

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► Hydroperoxyl radicals play an important role in VUV photolysis.
► Pulse radiolysis is used to study degradation mechanism of p-NP attacked by OH, OH + O2, OH + O2 + HO2.
► The relative amount of HO2 to that of OH matters to the observed phenomenon.
► The synergic effect of O2 and HO2 on the degradation of p-NP can be distinguished from each other.
► Hydroperoxyl radicals promote the ring open of p-NP intermediates.