9619885 Hoffmann This is an award to provide support for research on use of titanium dioxide as a catalyst in a photocatalytic process for treatment of aqueous and gaseous waste streams to reduce their pollutional impact on the receiving environment. The goal of this project is to determine whether the rate of the photochemical reaction can be significantly increased in aqueous heterogeneous media to levels comparable to those obtained in application of the photocatalytic process to gas-phase waste streams. The research is designed to address the fundamental basis for this apparent discrepancy by studying the reaction mechanism using a pulsed source of ultraviolet radiation. Two hypotheses are planned to be examined. One is that the difference in reactivities between the process application to liquids and gases relates to differences in the mode of substrate adsorption on the surface of the aatalyst. The other is that water may inhibit oxygen reduction and/or substrate competition for available adsorption sites on the target compound. Results of this project are expected to contribute to a better understanding than now exists of photochemical reactions as they may be applied to decontamination of soil and water. This in turn is likely to result in improvement of the engineering design of processes that can be used reduce the pollutional effect of liquid and gaseous waste discharges on the quality of surface and groundwater and to decontaminate soil.***
