| Abstract
| - To address some of the fundamental questions regardingthe kinetics of reduction of contaminants by zero-valentiron (Fe0), we have taken advantage of the masstransportcontrol afforded by a polished Fe0 rotating diskelectrode(RDE) in an electrochemical cell. The kinetics ofcarbontetrachloride (CCl4) dechlorination at an Fe0RDE werestudied in pH 8.4 borate buffer at a potential at which anoxide film would not form. In this system, thecathodiccurrent was essentially independent of electrode rotationrate, and the measured first-order heterogeneous rateconstant for the chemical reaction (kct = 2.3× 10-5 cms-1)was less than the estimated rate constant for masstransferto the surface. Thus, for the conditions of this study,therate of reduction of CCl4 by oxide-free Fe0appears to bedominated by reaction at the metal−water interfaceratherthan by transport to the metal surface. Activationenergiesfor reduction of CCl4 and hexachloroethane byoxide-covered granular Fe0 (measured in batchsystems)also indicate that overall rates are limited by reactionkinetics. Since mass transport rates vary little amongthechlorinated solvents, it is likely that variation inkct isprimarily responsible for the wide range of dechlorinationrates that have been reported for batch and columnconditions.
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