Using gas chromatography with electron capture detection (GC/ECD) to predict dehalogenation rates of environmental contaminants by zerovalent iron

The use of zerovalent iron (Fe⁰) in permeable reactive barriers (PRB) is a promising technology for remediating groundwater contaminated with halogenated hydrocarbons. A study was carried out to determine internally consistent sets of kinetic data by treating chlorinated alkanes, e.g., trichloromethane, dichloromethane, 1,2,3-trichloropropane, and 1,4-dichlorobutane, with Fe⁰ in aqueous solution under strictly controlled conditions; measure the vertical attachment energies (VAE) and dissociative electron attachment (DEA) cross-sections using electron scattering apparatus; and measure the ECD equimolar response function using GC/ECD. Good correlations were observed between the surface area normalized rate constants (KSA) with ECD response, VAE, and thermal DEA crosssections. The lower the VAE and the higher the near zero energy DEA cross-sections of chloroalkanes, the greater the ECD response and KSA of the compounds. ECD response, as well as descriptors determined from electron scattering techniques, might be potentially useful in predicting the dehalogenation rates of chlorinated contaminants treated with zerovalent iron. This is an abstract of a paper presented at the 228th ACS National Meeting (Philadelphia, PA 8/22-26/2004).