Development of Ozone Self-Decomposition Model for Engineering Design

Abstract

Recently, due to the advancement of O3/H2O2 treatment processes, it has been necessary to further develop the ozone self-decomposition radical model, which includes a variety of radical reactions, because the hydroxyl radical concentration as well as the ozone concentration must be taken into consideration. In this study, an ozone self-decomposition model that is meaningful for environmental engineering design under the practically encountered pH condition in the time scale of water treatment is proposed. First, an overall description model of ozone self-decomposition is developed based on the experimental results. The evaluation clarifies that the ozone self-decomposition can be formulated by a second-order reaction and the rate constant is enhanced 5 times and 2.2 times with increase of one pH unit and 5°C increase of temperature, respectively. Then a radical reaction model was developed. All of the reaction rate constants included in the model are obtained from the literature review except for the reaction rate constant of ozone with hydroxyl radical, which is obtained as 9.0 × 105 M−1s−1 based on experimental data. Good agreements of calculated results by the model with experimental results under the pH range from 2.7 to 7.8 over 10 minutes are obtained. This radical model of ozone self-decomposition will be applicable in analyzing other reactions, such as the effect of bicarbonate/carbonate ion on ozone self-decomposition, reaction with organic matter, the fate of micropollutants and by-products with ozone as well as hydroxyl radical.