Aqueous oxidation of trichloroethene (TCE): a kinetic analysis

An empirical kinetic rate law appropriate for many ground waters (neutral p H, aerobic) has been determined for the aqueous oxidation of trichloroethen e (TCE), one of the most volumetrically important chlorinated hydrocarbon p ollutants. Mass balances were monitored by measuring both the rate of disap pearance of TCE and the rate of appearance of CO2 and Cl-. Dilute buffer so lutions were used to fix pH and stoichiometrically sufficient amounts of di ssolved O-2 were used to make the reactions pseudo zero-order in O-2 Using a standard chemical kinetic approach, two orders-of-magnitude in initial TC E concentration were spanned and the resulting double-log plot (log concent ration vs. log initial rate) was used to determine the rate constant (k = 5 .77 +/- 1.06x10(-7) s(-1)) and "true" (i.e., with respect to concentration, not time) reaction order (n(c) = 0.85 +/- 0.03) for the rate law. By deter mining rate constants over the temperature interval 343-373 K, the Arrheniu s activation energy (E-a) for the reaction was determined to be 108.0 +/- 4 .5 kJ/mol. The rate law and derived kinetic parameters may be used in react ive transport simulators in order to account for aqueous oxidation of TCE a s a function of temperature. (C) 1999 Elsevier Science Ltd. All rights rese rved.