Quantification\nof the Contribution of Heterogeneous\nSurface Processes to Pollutant Abatement during Heterogeneous Catalytic\nOzonation

Heterogeneous\nsurface processes such as adsorption and oxidation\nwith surface-adsorbed reactive oxygen species (ROS<sub>ad</sub>, e.g.,\nadsorbed oxygen atom (*O<sub>ad</sub>) and hydroxyl radicals (<sup>•</sup>OH<sub>ad</sub>)) have been suggested to play an important\nrole in pollutant abatement during heterogeneous catalytic ozonation\n(HCO). However, to date, there is no reliable method to quantitatively\nevaluate the contribution of heterogeneous surface processes to pollutant\nabatement (<i>f</i><sub>S</sub>) during HCO. In this study,\nwe developed a method by combining probe compound-based experiments\nwith kinetic modeling to distinguish heterogeneous surface processes\nfrom homogeneous bulk reactions with aqueous O<sub>3</sub> and ROS\n(<sup>•</sup>OH and superoxide radicals (O<sub>2</sub><sup>•–</sup>) in the abatement of various pollutants (e.g.,\natrazine, ibuprofen, tetrachloroethylene, and perfluorooctanoic acid)\nduring HCO with reduced graphene oxide. The results show that the\npollutants that have a low affinity for the rGO surface (e.g., ibuprofen\nand tetrachloroethylene) were essentially abated by homogeneous bulk\nreactions, while the contribution of heterogeneous surface processes\nwas negligible (<i>f</i><sub>S</sub> < 5%). In contrast,\nheterogeneous surface processes played an important or even dominant\nrole in the abatement of pollutants that have a high surface affinity\n(e.g., <i>f</i><sub>S</sub> = 32–82% for atrazine\nand perfluorooctanoic acid). This study is a critical first step in\nquantitatively evaluating the role of heterogeneous surface processes\nfor pollutant abatement during HCO, which is crucial to understanding\nthe mechanism of HCO and designing catalysts for effective pollutant\nabatement.