A column study of geochemical factors affecting reductive dechlorination of chlorinated solvents by zero-valent iron
- Oregon Graduate Inst. of Science and Technology, Portland, OR (United States). Dept. of Environmental Science and Engineering
Laboratory and field studies have shown that fillings of metal that are predominantly Fe{sup 0} can rapidly dehalogenate a variety of chlorinated solvents, and several technologies have recently been proposed to use this reaction in remediation of contaminated ground water. This report describes results from a laboratory column designed to model the spatial distribution of chemical conditions when iron is applied as part of an in-situ permeable reactive barrier. The column contains a zone of granular iron located between up-gradient and down-gradient zones of sand, and has received deionized water with varying concentrations of CCl{sub 4} for over 6 months. Aerobic corrosion results in complete consumption of dissolved oxygen and precipitation of ferric hydroxides at the interface where water enters the iron-bearing zone. Within the iron-bearing zone, corrosion continues due to oxidation of the iron by water and carbon tetrachloride, resulting in increased pH and concentration of dissolved iron in the pore water. At the down-gradient interface, pH decreased as the result of precipitation of iron-bearing minerals. Carbon tetrachloride (up to 1.6 mM) was fully dehalogenated by the first sample port within the iron-bearing zone. The chloroform produced was further dechlorinated to dichloromethane, but at a slower rate. First-order disappearance kinetics for chloroform applied across the zone of iron, and k{sub obs} has changed little over several months. No evidence has been found so far for unusual reactivity of the chlorinated solvents at either the up-gradient or down-gradient interfaces.
- OSTI ID:
- 398082
- Report Number(s):
- CONF-941124-; ISBN 0-935470-85-9; TRN: IM9649%%290
- Resource Relation:
- Conference: 33. Hanford symposium on health and the environment: symposium on in-situ remediation--scientific basis for current and future technologies, Richland, WA (United States), 7-11 Nov 1994; Other Information: PBD: 1994; Related Information: Is Part Of In-situ remediation: Scientific basis for current and future technologies. Part 2; Gee, G.W. [ed.] [Pacific Northwest Lab., Richland, WA (United States)]; Wing, N.R. [ed.] [Westinghouse Hanford Co., Richland, WA (United States)]; PB: 605 p.
- Country of Publication:
- United States
- Language:
- English
Similar Records
Oxygen controlled product formation in CCl{sub 4} dechlorination using zero-valent iron
Reductive dechlorination of aliphatic and aromatic compounds by zero-valent metals