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

在一项为期一年的研究中，研究小组提出研究氯化苯酚和取代苯酚的氧化动力学——在紫外线和TiO2的存在下——这两类化合物包括EPA列出的129种优先污染物中的24种。研究结果将有助于环境工程师开发用于水和废水处理的光催化氧化技术。提案研究的目的是：1。光催化氧化动力学或三种不同类别的有机物，即氯化芳烃，取代芳烃，他们之间的竞争氧化将进行研究。每个有机类别中的模型化合物将被广泛研究吸附和氧化。氧化动力学将用Langmuir- Hinshelwood方程进行数学建模。获得的动力学参数将用于根据给定水质下的分子结构-反应性关系估计该类中其他有机物的氧化参数。2. 研究了pH值、溶解氧、碱度和硬度等水质对Hammett地块的影响。温度和光强度对不同类型有机污染物的影响也将被研究。3. 当溶液中同时存在超过一种底物时，就会形成竞争性氧化动力学。根据分子参数、水质、温度、光照强度等因素建立数学模型，预测给定水质和有机混合物下给定有机化合物的氧化速率。4. 以pH为主变量，通过Hammett图区分不同实验条件下不同有机化合物的羟基自由基攻击和正空穴氧化等基本机理。

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.