Different Behavior of H2O2 in Aldicarb and Hexazinone Oxidized By O3/H2O2

Different Behavior of H₂O₂ in Aldicarb and Hexazinone Oxidized by O₃/H₂O₂

Abstract: The degradation of hexazinone and aldicarb by direct ozonation and an advanced oxidation process (AOP) of O₃/H₂O₂ were investigated in this study with the focus on the oxidation mechanism by identifying the hydrogen peroxide consumption during the oxidation process of the two chemicals. The results show H₂O₂ could enhance the removal rate of the triazine herbicide hexazinone, and it consumes along with the variation of removal rate in the light of different pH levels. The addition of H₂O₂ contributes little to the removal of the thiocarbamate herbicide aldicarb and the H₂O₂ content kept constant throughout the degradation process. Tert-butyl alcohol (TBA) effectively scavenges the OH radical effectively for hexazinone, but had no effect on the removal rate of aldicarb. Aldicarb removal mainly attribute to direct oxidation of the ozone molecule in both O₃ (97% ) and O₃/H₂O₂ (96.76%) systems .Moreover, sole O₃ could hardly oxidize hexazinone whereas OH radicals contribute respectively 74.7% and 97.5% of removal in O₃ system and O₃/H₂O₂ AOP. All of these findings which are contrast to the conclusions of formers suggest that the mechanism of OH radical generation and the chain reaction in O₃/H₂O₂ AOP should be further discussed.

Key words: hexazinone; aldicarb; O₃/H₂O₂; direct and indirect oxidation; H₂O₂ consumption