Aqueous oxidation of trichloroethene (TCE): a kinetic analysis

An empirical kinetic rate law appropriate for many ground waters (neutral pH, aerobic) has been determined for the aqueous oxidation of trichloroethene (TCE), one of the most volumetrically important chlorinated hydrocarbon pollutants. Mass balances were monitored by measuring both the rate of disappearance of TCE and the rate of appearance of CO2 and Cl−. Dilute buffer solutions were used to fix pH and stoichiometrically sufficient amounts of dissolved O2 were used to make the reactions pseudo zero-order in O2. Using a standard chemical kinetic approach, two orders-of-magnitude in initial TCE concentration were spanned and the resulting double-log plot (log concentration vs. log initial rate) was used to determine the rate constant (k=5.77±1.06×10−7 s−1) and “true” (i.e., with respect to concentration, not time) reaction order (nc=0.85±0.03) for the rate law. By determining rate constants over the temperature interval 343–373 K, the Arrhenius activation energy (Ea) for the reaction was determined to be 108.0±4.5 kJ/mol. The rate law and derived kinetic parameters may be used in reactive transport simulators in order to account for aqueous oxidation of TCE as a function of temperature.