Grantee Research Project Results

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 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 will explore 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 is rapidly emerging as a highly promising approach for in situ treatment of groundwater contaminants, but its applicability to vapor phase contaminants has been virtually unexplored. In this project we propose to complement and significantly extend the scope of investigations recently initiated (though funding obtained from other sources) that pertain to use of zero-valent metals for treatment of anoxic landfill gases. Specifically, in this project we intend to test whether similar treatment systems could prove useful for treating organohalides in gas streams that contain O₂. Although it might be anticipated that the presence of O₂ could lead to more rapid passivation of reactive surfaces and hence decreased reactivity, there is also ample reason to believe that the presence of O₂ will not significantly impair treatment system performance, provided that the reactive surface is judiciously selected. If successful, an approach based on zero valent metals or bimetallic reductants could be used to treat offgases obtained from soil vapor extraction (SVE) systems. Results will form the basis of process models that can be used to design aboveground treatment systems for SVE offgases that contain organohalides.

Approach:

We propose to study reactions of selected organohalide contaminants with a variety of bimetallic reductants (or iron alone). Initial work (Task 1) will involve screening reductants for reactivity and selectivity in batch systems containing dissolved oxygen. Once promising candidates are identified, performance and longevity studies will be initiated in column reactors in which contaminants will be introduced to a gas phase containing O₂ (Task 2). Reaction rates and products will be monitored over time for several different metal or bimetallic reductants. Specifically, we will explore the influence of the presence of oxygen on reactivity and selectivity. We will also examine whether reactivity declines over time as the composition of the metal or bimetallic reductant surface evolves. Analytical instrumentation to be purchased with this grant will allow us to assess how the changing composition of the solution phase affects reactivity of the metal or bimetallic reductant. In Task 3, the batch and column studies will be complemented by surface chemical investigations (involving surface infrared spectroscopy, scanning Auger electron spectroscopy, X-ray photoelectron spectroscopy, and in situ scanning electron microscopy). These studies will provide information concerning the composition of the reactive surface.

Expected Results:

It is expected that certain zero-valent metal or bimetallic reductants will degrade halogenated contaminants even in the presence of O₂. This project will provide information needed to assess whether such treatment processes are cost-effective over the projected design life of the treatment process.

Improvements in Risk Management:

The proposed treatment of offgas from SVE systems represents a significant improvement over existing treatment technologies (e.g., adsorption onto granular activated carbon), which merely transfer contaminants from one medium to another.

Publications and Presentations:

Publications have been submitted on this subproject: View all 4 publications for this subproject | View all 108 publications for this center

Journal Articles:

Journal Articles have been submitted on this subproject: View all 2 journal articles for this subproject | View all 20 journal articles for this center

Supplemental Keywords:

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

Progress and Final Reports:

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