Modeling Tetrachloroethylene Decomposition in Photosonolysis Reactor

A mathematical model was developed for the decomposition of halogenated compounds in water and applied for tetrachloroethylene (PCE) in a flow-through photosonolysis reactor. To develop the model, a series of differential equations were formulated based on the principles of conservation of mass and mass action for hypothetical parent and daughter species, which were then solved analytically. The model sensitivity analysis was performed to determine if the model gives intuitive results. In support of the modeling effort, experiments were conducted. In a flow-through bench-scale reactor, simulated groundwater contaminated with PCE was irradiated with ultraviolet light and ultrasound concurrently in the presence of titanium dioxide (TiO2). The model was calibrated against the concentrations of PCE, trichloroethylene, methylene chloride, and chloride ion, obtained from the experiments. The proposition for the rate constants is based on fitting the model result to the experimental data. The model was further verified by comparing the model results against a different set of experimental data. The model results against available data indicated good agreement within experimental variations. The modeling suggests that PCE is more susceptible to the C-C double bond cleavage than the C-Cl bond cleavage. The results also support the assumptions that chlorinated methane compounds can be degraded at higher rates than chlorinated ethylene and that the values of the degradation rate constants increase with a decreasing number of chlorine atoms attached to the hydrocarbon compound.