Grantee Research Project Results
Kinetics and Pathways of Chlorinated Ethylene and Chlorinated Ethane Reaction With Zero-Valent MetalsEPA Grant Number: U915160
Title: Kinetics and Pathways of Chlorinated Ethylene and Chlorinated Ethane Reaction With Zero-Valent Metals
Investigators: Arnold, William A.
Institution: Johns Hopkins University
EPA Project Officer: Jones, Brandon
Project Period: January 1, 1997 through January 1, 2000
Project Amount: $102,000
RFA: STAR Graduate Fellowships (1997)
Research Category: Engineering and Environmental Chemistry , Academic Fellowships , Fellowship - Civil/Environmental Engineering
The objective of this research project is to determine the kinetics and pathways of chlorinated ethylene and ethane reaction with zero-valent metals to develop a model for use in process optimization. The degradation of chlorinated solvents through the use of zero-valent metals as reductants represents a promising new approach for treating groundwater contaminated with such solvents. In order to successfully design treatment systems, information is needed concerning the kinetics and pathways through which transformations occur. The principal objective of this project is to determine the kinetics and pathways of chlorinated ethylene and ethane reaction with zero-valent metals in order to develop a model for use in process optimization.Approach:
Experiments are conducted in both batch and column reactors using a deoxygenated buffer solution that is spiked with the contaminant of interest. Reactions are runconducted over a range of initial concentrations in order to determine the influence of concentration on reaction rate. At specified intervals, aqueous samples are removed from the batch reactors by injection of an equivalent volume of deoxygenated buffer solution or from the columns via ports in the side of the reactor. The aqueous samples are equilibrated with air, and headspace samples are analyzed using gas chromatography (GC) with a flame ionization detector (FID). In this manner, the disappearance of the parent compound and production of daughter species are monitored. Using the concentration versus time data, rate constants are calculated. When calculating the rate constants for a given species, the rate constants for reactions of intermediates detected in a given experiment are constrained to be equal to those determined in independent experiments in which the intermediates were introduced as the starting material. The rate of parent disappearance and product distribution data then are then used to determined the relative magnitudes of the competing reactions for the parent species.Supplemental Keywords:
fellowship, kinetics, chlorinated ethylene, chlorinated ethane, zero-valent metals, chlorinated solvents, groundwater, gas chromatography, GC, flame ionization detector, FID, rate constant.