Revisiting the role of reactive oxygen species for pollutant abatement during catalytic ozonation: The probe approach versus the scavenger approach

This study evaluated the role of reactive oxygen species (ROS) for pollutant abatement during catalytic ozonation by the conventional scavenger approach and a proposed probe approach. Results show that the addition of high-concentration ROS scavengers (2 mM tert-butanol or 0.63 mM para-benzoquinone) fundamentally changes the reaction mechanisms of catalytic ozonation. Therefore, the conventional scavenger approach actually cannot realistically reflect the role of ROS (•OH and O2•–) for pollutant abatement during water treatment by catalytic ozonation. In contrast, spiking low-concentration ROS probes (0.64 μM p-chlorobenzoic acid and 0.42 μM chloroform) to measure ROS exposures during catalytic ozonation would not noticeably influence the reaction mechanisms. Based on the measured ROS exposures, pollutant abatement could be satisfactorily simulated using chemical kinetic models. Furthermore, the respective contribution of various ROS for pollutant abatement could be quantitatively evaluated. Therefore, the probe approach can provide a more useful method to reveal catalytic ozonation mechanisms.