Sulfate radical-induced incorporation of NO2 group into chlorophenols

Abstract

Sulfate radical ( $${\text{SO}}_{4}^{ \cdot - }$$ )-based advanced oxidation processes (SR-AOPs) are promising in situ chemical oxidation technologies that received increasing interest recently. The application of SR-AOPs for decontamination may, however, generate unexpected toxic by-products. This contribution reports that $${\text{SO}}_{4}^{ \cdot - }$$ can incorporate nitrite (NO2−) nitrogen into chlorophenols, resulting in the formation of chloronitrophenols which pose greater environmental concerns. Nitrogen dioxide radical ( $${\text{NO}}_{2}^{ \cdot }$$ ) and phenoxy radical are important precursors responsible for the formation of chloronitrophenols. High concentrations of NO2− inhibited the transformation of chlorophenol but promoted the formation of chloronitrophenol. This study underscores a need for caution in the application of SR-AOPs in the presence of NO2−, because chloronitrophenols can be more genotoxic and mutagenic than chlorophenols.