Quantification of the Contribution of Heterogeneous Surface Processes to Pollutant Abatement during Heterogeneous Catalytic Ozonation

Heterogeneous surface processes such as adsorption and oxidation with surface-adsorbed reactive oxygen species (ROS_ad, e.g., adsorbed oxygen atom (*O_ad) and hydroxyl radicals (^•OH_ad)) have been suggested to play an important role in pollutant abatement during heterogeneous catalytic ozonation (HCO). However, to date, there is no reliable method to quantitatively evaluate the contribution of heterogeneous surface processes to pollutant abatement (f_S) during HCO. In this study, we developed a method by combining probe compound-based experiments with kinetic modeling to distinguish heterogeneous surface processes from homogeneous bulk reactions with aqueous O₃ and ROS (^•OH and superoxide radicals (O₂^•-) in the abatement of various pollutants (e.g., atrazine, ibuprofen, tetrachloroethylene, and perfluorooctanoic acid) during HCO with reduced graphene oxide. The results show that the pollutants that have a low affinity for the rGO surface (e.g., ibuprofen and tetrachloroethylene) were essentially abated by homogeneous bulk reactions, while the contribution of heterogeneous surface processes was negligible (f_S < 5%). In contrast, heterogeneous surface processes played an important or even dominant role in the abatement of pollutants that have a high surface affinity (e.g., f_S = 32-82% for atrazine and perfluorooctanoic acid). This study is a critical first step in quantitatively evaluating the role of heterogeneous surface processes for pollutant abatement during HCO, which is crucial to understanding the mechanism of HCO and designing catalysts for effective pollutant abatement.