Grantee Research Project Results

2003 Progress Report: Zero-Valent Metal Treatment of Halogenated Vapor-Phase Contaminants in SVE Offgas

EPA Grant Number: R828771C006
Subproject: this is subproject number 006 , established and managed by the Center Director under grant R828771
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
Center: Center for the Study of Childhood Asthma in the Urban Environment
Center Director: Hansel, Nadia
Title: Zero-Valent Metal Treatment of Halogenated Vapor-Phase Contaminants in SVE Offgas
Investigators: Roberts, A. Lynn , Fairbrother, D. Howard
Institution: The Johns Hopkins University
EPA Project Officer: Aja, Hayley
Project Period: October 1, 2001 through September 30, 2002
Project Period Covered by this Report: October 1, 2002 through September 30, 2003
Project Amount: Refer to main center abstract for funding details.
RFA: Hazardous Substance Research Centers - HSRC (2001) Recipients Lists
Research Category: Hazardous Waste/Remediation , Land and Waste Management

Objective:

This research explores the use of zero-valent metals and bimetallic reductants for treating vapor-phase organohalides found in offgas from soil vapor extraction systems. Zero-valent metal technology has emerged as a highly promising approach for in situ treatment of groundwater contaminants, but its applicability to vapor-phase contaminants previously had been virtually unexplored. This project significantly extended the scope of investigations that were carried out in parallel to this study (with funding obtained from other sources) that pertained to the use of zero-valent metals for treatment of anoxic landfill gases. Specifically, in this project we tested whether similar treatment systems could prove useful for treating organohalides in gas streams that contained O2 (as would be anticipated for soil vapor extraction [SVE] offgas, but not within typical landfill gas).

Progress Summary:

During the first year of this project, preliminary work focused on screening the reactivity of various iron-based, bimetallic reductants. The rates of reaction of cis-1,2-dichloroethylene (cis-DCE), employed as a "model" organohalide, were studied in batch reactors as a function of the identity of the catalytic metal in bimetallic systems. Initial experiments compared the rates of Ni/Fe, Co/Fe, and Cu/Fe reductants to that of Fe alone. These studies revealed significant differences between the various reductants. Although Co/Fe and Cu/Fe exhibited slightly accelerated rates of reaction as compared to Fe alone, the reaction rates with Ni/Fe were significantly faster.

Subsequent batch experiments during the remainder of the first year of effort emphasized Ni/Fe reductants. In additional batch experiments, we investigated the effect of nickel loading on the overall rate of reaction. Reaction products also were quantified. Displacement plating methods were used to vary the surface loading of the catalytic metal. Auger electron spectroscopy was used to determine the average, surficial, nickel loading on the iron particles. Comparison of the reaction rate data from the batch reactor studies with the surface composition information indicates that the nickel loading has a significant impact on the rate of reduction of cis-DCE. At low Ni loadings, the rate of cis-DCE removal increases quickly with nickel concentration, but at higher Ni loadings the rate increases more slowly. At the highest nickel loading attained, the Ni/Fe system exhibited rates of cis-DCE reduction 20 times greater than those attained with Fe alone. Note that pure Ni powder was found to be unreactive with cis-DCE. Higher nickel loadings also were found to favor the generation of more fully dechlorinated products, and to result in a lower yield of vinyl chloride.

Efforts during the second year of this project focused on testing the applicability of the Fe and Ni/Fe bimetallic reductants to the treatment of gas-phase contaminants in column reactors. Plexiglas columns, fitted with a series of gas sampling ports along their lengths, were packed with either iron or nickel-plated iron, filled with water, and allowed to drain gravimetrically. cis-DCE was introduced to the gas phase by bubbling either a 50:50 mix of CO2/N2 (to simulate anaerobic landfill gas) or compressed air (to simulate aerobic SVE offgas) through a saturated solution of the organohalide. Two columns were packed with Fe alone, and two were packed with a Ni/Fe (40 percent Ni) bimetallic reductant. One Fe and one Ni/Fe column were used to treat cis-DCE in an aerobic gas stream, and the other two columns were used to treat an anaerobic gas stream. The concentration of the organohalide could be accurately manipulated by varying the ratio of the cis-DCE containing gas stream with a second, water saturated gas stream.

Samples periodically were removed from the ports for gas chromatographic analysis of parent compounds and reaction products. The columns were continuously exposed to cis-DCE for an extended period of time to allow us to study the reactivity and longevity of the Ni/Fe and Fe(0) reductants. The Ni/Fe columns initially performed much better than the Fe columns, with 100 percent cis-DCE initial removal in the former, versus 0-60 percent in the latter. Over time, however, the performance of all of the columns deteriorated. Eventually the performance of the Ni/Fe columns deteriorated to a level comparable to that of the iron columns. This occurred more rapidly under aerobic conditions (approximately 7 days) than under anaerobic conditions (approximately 32 days). The initial reactivity could largely be regenerated, at least on a temporary basis, by passing a 1 M HCl solution through the columns, then rinsing them with deionized water.

Future Activities:

This project has been completed. We will revise manuscripts as needed for publication.

Journal Articles on this Report : 2 Displayed | Download in RIS Format

Publications Views

Other subproject views:	All 4 publications	2 publications in selected types	All 2 journal articles
Other center views:	All 108 publications	22 publications in selected types	All 20 journal articles

Publications

Type	Citation	Sub Project	Document Sources
Journal Article	McGuire MM, Carlson DL, Vikesland PJ, Kohn T, Grenier AC, Langley LA, Roberts AL, Fairbrother DH. Applications of surface analysis in the environmental sciences: dehalogenation of chlorocarbons with zero-valent iron and iron-containing mineral surfaces. Analytica Chimica Acta. 2003;496(1-2):301-313.	R828771C006 (2003) R828164 (Final)	not available
Journal Article	Grenier AC, McGuire MM, Fairbrother DH, Roberts AL. Treatment of vapor-phase organohalides with zero-valent iron and Ni/Fe reductants. Environmental Engineering Science. 2004;21(4):421-435.	R828771C006 (2003)	not available

Supplemental Keywords:

adsorption, chemical detection techniques, chemical kinetics, chemical releases, contaminant dynamics, contaminant transport, contaminated sediment, electrochemical technology, fate and transport, fate and transport, groundwater, hazardous waste treatment, heavy metal contamination, heavy metals, offgas, soil extraction, soil vapor extraction, SVE, soil vapor phase contaminants, vapor phase organohalides, waste reduction, pollution prevention, environmental engineering., RFA, Scientific Discipline, Waste, Water, Hydrology, Chemical Engineering, Contaminated Sediments, Geochemistry, Health Risk Assessment, Environmental Chemistry, Analytical Chemistry, Hazardous Waste, Ecology and Ecosystems, Ecological Risk Assessment, Hazardous, Environmental Engineering, Engineering, Chemistry, & Physics, fate and transport, hazardous waste treatment, soil vapor phase contaminants, electrochemical technology, vapor phase organohalides, contaminant transport, fate and transport , contaminant dynamics, contaminated sediment, soil extraction, adsorption, chemical detection techniques, chemical kinetics, zero valent metal treatment, chemical releases, offgas, heavy metal contamination, soil vapor extraction, groundwater

Relevant Websites:

http://www.jhu.edu/hsrc/ Exit

Progress and Final Reports:

Original Abstract

Final

Main Center Abstract and Reports:

R828771    Center for the Study of Childhood Asthma in the Urban Environment

Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
R828771C001 Co-Contaminant Effects on Risk Assessment and Remediation Activities Involving Urban Sediments and Soils: Phase II
R828771C002 The Fate and Potential Bioavailability of Airborne Urban Contaminants
R828771C003 Geochemistry, Biochemistry, and Surface/Groundwater Interactions for As, Cr, Ni, Zn, and Cd with Applications to Contaminated Waterfronts
R828771C004 Large Eddy Simulation of Dispersion in Urban Areas
R828771C005 Speciation of chromium in environmental media using capillary electrophoresis with multiple wavlength UV/visible detection
R828771C006 Zero-Valent Metal Treatment of Halogenated Vapor-Phase Contaminants in SVE Offgas
R828771C007 The Center for Hazardous Substances in Urban Environments (CHSUE) Outreach Program
R828771C008 New Jersey Institute of Technology Outreach Program for EPA Region II
R828771C009 Urban Environmental Issues: Hartford Technology Transfer and Outreach
R828771C010 University of Maryland Outreach Component
R828771C011 Environmental Assessment and GIS System Development of Brownfield Sites in Baltimore
R828771C012 Solubilization of Particulate-Bound Ni(II) and Zn(II)
R828771C013 Seasonal Controls of Arsenic Transport Across the Groundwater-Surface Water Interface at a Closed Landfill Site
R828771C014 Research Needs in the EPA Regions Covered by the Center for Hazardous Substances in Urban Environments
R828771C015 Transport of Hazardous Substances Between Brownfields and the Surrounding Urban Atmosphere