Atmospheric heterogeneous reaction of chlorobenzene on mineral α-Fe2O3 particulates: a chamber experiment study

Despite the large emission of chlorinated volatile organic compounds (CVOCs) into the atmosphere, the ultimate fate of these compounds remains largely unknown. Herein, we explore the photochemical conversion of an important class of CVOCs, namely chlorobenzene (CB), on mineral a-Fe2O3 particulates under atmospheric relevant conditions. A series of chamber reactions composed of the CB with/without SO2 or NO2 are performed, followed by in situ diffuse reflectance infrared Fourier transform spectroscopy measurements and density functional theory calculations. We show that CB can be considerably degraded by a-Fe2O3 under light irradiation, whereas the reaction is markedly suppressed by adding SO2 or NO2 owing to their competitive adsorption and surface acidification. In particular, we discover that CB can be ultimately converted into polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) under dark state or light irradiation, suggesting a possible origin of atmospheric PCDD/Fs from this overlooked photochemical source.

Automated summary

This study explores the photochemical conversion of chlorobenzene (CB), an important class of chlorinated volatile organic compounds (CVOCs), on mineral a-Fe2O3 particulates under atmospheric relevant conditions. It is found that CB can be significantly degraded by a-Fe2O3 under light irradiation, but the reaction is suppressed by the addition of SO2 or NO2 due to competitive adsorption and surface acidification. Additionally, CB can ultimately be converted into polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) under dark or light conditions, providing a possible origin of atmospheric PCDD/Fs from this overlooked photochemical source.