Sulfate radical-induced incorporation of NO2 group into chlorophenols

Sulfate radical (SO4-)-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 SO4- can incorporate nitrite (NO2-) nitrogen into chlorophenols, resulting in the formation of chloronitrophenols which pose greater environmental concerns. Nitrogen dioxide radical (NO2) 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.