Determination of Hydroperoxyl/superoxide Anion Radical (HO₂¤y/O₂¤y-) Concentration in the Decomposition of Ozone Using a Kinetic Method

摘要

A novel kinetic method for determination of HO₂·/O₂·- in ozone decomposition in water is described. In this study, potential interferences of O₃ and the hydroxyl radicals, ·OH_(O3), are suppressed by HSO₃-/SO₃2-. HO₂·/O₂·- formed in ozone decomposition reduces Fe3+-EDTA into Fe2+-EDTA and subsequently the well-known Fenton-like (FL) reaction of H₂O₂ and Fe2+-EDTA produces the hydroxyl radicals, ·OH_(FL). Benzoic acid (BA) scavenges ·OH_(FL) to produce OHBA, which are analyzed by fluorescence detection (ルex = 320 nm and ルem = 400 nm). The concentration of HO₂·/O₂·- in ozone decomposition has been determined by the novel kinetic method using the experimentally determined half-life (t_1/2). The steady-state concentration of HO₂·/O₂·- is proportional to the O₃ concentration at a given pH. However, the steady-state concentration of HO₂·/O₂·- in ozone decomposition is inversely proportional to pH values. This pH dependence is due to significant loss of O₂·- by O₃ at higher pH conditions. The steady-state concentrations of HO₂·/O₂·- are in the range of 2.49 (【 0.10) 】 10-9 M (pH = 4.17) ~ 3.01 (【 0.07) 】 10-10 M (pH = 7.59) at [O₃]_o = 60 レM.