Rate-limiting mechanisms for carbon tetrachloride and trichloroethylene reactions at iron surfaces

The rate limiting mechanisms for reductive dechlorination of carbon tetrachloride (CT) and trichloroethylene (TCE) involve electron transfer were studied. The temperature dependencies of the transfer coefficients and reaction rates were used to assess whether the rate limiting mechanisms for TCE and CT reduction involved electron transfer. The transfer coefficient for CT reduction was independent of temperature, while that for TCE reduction was temperature dependent, indicating that the rate of CT reduction was limited by an electron transfer step, while that for TCE was limited by chemical dependent factors. The apparent activation energies for CT reduction decreased with increasingly negative electrode potentials. This suggested that the rate of CT dechlorination is controlled by an electron transfer step. The rate-limiting step for TCE dechlorination did not involve electron transfer. This is an abstract of a paper presented at the 221st ACS National Meeting (San Diego, CA 4/1-5/2001).