(215b) 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