RIMI: Photocatalytic Oxidation Kinetics of Priority OrganicPollutants by TiO2 - A Molecular Structure and Reactivity Study

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In a one-year study, the research term proposed to study the kinetics of the oxidation--in the presence of UV light and TiO2--of chlorinated phenols and substituted phenols which are two classes of compounds that include 24 of the 129 priority pollutants listed by EPA. The intent is that the results will aid environmental engineers in the development of photocatalytic oxidation techniques for water and wastewater treatment. Objectives of the proposal research are: 1. Photocatalytic oxidation kinetics or organics for three different classes, namely, chlorinated aromatics, substituted aromatics, competitive oxidation between them will be investigated. A model compound in each organic class will be extensively studied for both adsorption and oxidation. The oxidation kinetics will be mathematically modeled by Langmuir- Hinshelwood equation. The kinetic parameters obtained will be used to estimate the oxidation parameters of other organics in the class according to molecular structure-reactivity relations at a given water quality. 2. The effects of water quality such as pH, dissolved oxygen, alkalinity, and hardness on the Hammett plot will be studied. The effect of temperature and light intensity will also be investigated for different classes of organic pollutants. 3. When more than on substrate coexist in the solution, a competitive oxidation kinetics will be established. A mathematic model will be constructed according to molecular parameters, water qualities, temperature, and light intensity to predict the oxidation rate for a given organic compound at a given water quality and organic mixture. 4. Fundamental mechanisms such as hydroxyl radical attack and positive hole oxidation will be differentiated under different experimental conditions for different organic compounds through Hammett plots by using pH as the master variable.