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Title: Overcoming Barriers to the Remediation of Carbon Tetrachloride through Manipulation of Competing Reaction Mechanisms-Final Technical Report

Abstract

The premise of this project was that if we understood the fundamental chemistry that controls the branching among product formation pathways for the degradation of CCl₄, we could design remediation strategies that minimize the formation of CHCl₃ and thereby provide badly needed alternatives for remediation of the large plumes of CCl₄ that contaminate several DOE sites. To this end, we performed a series of coordinated batch, spectroscopic, and modeling experiments, to study the effect of a variety of factors on the yield of CHCl₃ from CCl₄ during reduction with zero-valent iron (Fe⁰). The factors studied include those with direct implications for field performance (e.g., the concentration of CCl₄ relative to the amount of iron surface area) and others chosen for diagnosis of the reaction mechanism (e.g., incorporation of deuterium into CCl₄ reduction products in the presence of D₂O). The key mechanistic findings of this study are (i) that CCl₃• probably is not an intermediate in the formation of CF, but CCl₃⁻ probably is, (ii) the high reductive capacity of the Fe⁰ core favors the concerted 2e⁻ reduction, and (iii) magnetite on Fe⁰ favors the benign product formation pathway. The latter conclusion is based on the observation that one type ofmore » nano-sized Fe⁰ that is coated with magnetite shell produces low yields of chloroform (0-40%), whereas others produce the higher yields of chloroform (60-100%) that are typical of most methods for reducing CCl₄ (including biodegradation). Since nano-Fe⁰ can, in principle, be introduced into the deep subsurface by injection, our results would suggest that the right type of nano-Fe⁰ introduced in the right way might be highly effective at dechlorinating CCl₄ with minimal formation of CHCl₃ or other undesirable by-products. This conclusion may offer a breakthrough in the search for remediation technologies that are suitable for the deep CCl₄-contamination at DOE sites such as the 200-W area of Hanford.« less

Authors:
; ;
Publication Date:
Research Org.:
Oregon Health & Science University; Pacific Northwest National Laboratory
Sponsoring Org.:
USDOE - Office of Environmental Management (EM)
OSTI Identifier:
900346
Report Number(s):
ER63485-F
TRN: US200717%%70
DOE Contract Number:  
FG07-02ER63485
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; BIODEGRADATION; CAPACITY; CARBON TETRACHLORIDE; CHEMISTRY; CHLOROFORM; DESIGN; DEUTERIUM; DIAGNOSIS; IRON; MAGNETITE; PERFORMANCE; PLUMES; REACTION KINETICS; SIMULATION; SURFACE AREA; Carbon Tetrachloride, Chloroform, Groundwater, Remediation, In Situ Chemical Reduction, Dechlorination, Zerovalent Iron Metal, Nanoparticles

Citation Formats

Tratnyek, Paul G, Amonette, James E, and Bylaska, Eric J. Overcoming Barriers to the Remediation of Carbon Tetrachloride through Manipulation of Competing Reaction Mechanisms-Final Technical Report. United States: N. p., 2007. Web. doi:10.2172/900346.
Tratnyek, Paul G, Amonette, James E, & Bylaska, Eric J. Overcoming Barriers to the Remediation of Carbon Tetrachloride through Manipulation of Competing Reaction Mechanisms-Final Technical Report. United States. doi:10.2172/900346.
Tratnyek, Paul G, Amonette, James E, and Bylaska, Eric J. Wed . "Overcoming Barriers to the Remediation of Carbon Tetrachloride through Manipulation of Competing Reaction Mechanisms-Final Technical Report". United States. doi:10.2172/900346. https://www.osti.gov/servlets/purl/900346.
@article{osti_900346,
title = {Overcoming Barriers to the Remediation of Carbon Tetrachloride through Manipulation of Competing Reaction Mechanisms-Final Technical Report},
author = {Tratnyek, Paul G and Amonette, James E and Bylaska, Eric J},
abstractNote = {The premise of this project was that if we understood the fundamental chemistry that controls the branching among product formation pathways for the degradation of CCl₄, we could design remediation strategies that minimize the formation of CHCl₃ and thereby provide badly needed alternatives for remediation of the large plumes of CCl₄ that contaminate several DOE sites. To this end, we performed a series of coordinated batch, spectroscopic, and modeling experiments, to study the effect of a variety of factors on the yield of CHCl₃ from CCl₄ during reduction with zero-valent iron (Fe⁰). The factors studied include those with direct implications for field performance (e.g., the concentration of CCl₄ relative to the amount of iron surface area) and others chosen for diagnosis of the reaction mechanism (e.g., incorporation of deuterium into CCl₄ reduction products in the presence of D₂O). The key mechanistic findings of this study are (i) that CCl₃• probably is not an intermediate in the formation of CF, but CCl₃⁻ probably is, (ii) the high reductive capacity of the Fe⁰ core favors the concerted 2e⁻ reduction, and (iii) magnetite on Fe⁰ favors the benign product formation pathway. The latter conclusion is based on the observation that one type of nano-sized Fe⁰ that is coated with magnetite shell produces low yields of chloroform (0-40%), whereas others produce the higher yields of chloroform (60-100%) that are typical of most methods for reducing CCl₄ (including biodegradation). Since nano-Fe⁰ can, in principle, be introduced into the deep subsurface by injection, our results would suggest that the right type of nano-Fe⁰ introduced in the right way might be highly effective at dechlorinating CCl₄ with minimal formation of CHCl₃ or other undesirable by-products. This conclusion may offer a breakthrough in the search for remediation technologies that are suitable for the deep CCl₄-contamination at DOE sites such as the 200-W area of Hanford.},
doi = {10.2172/900346},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Wed Mar 07 00:00:00 EST 2007},
month = {Wed Mar 07 00:00:00 EST 2007}
}

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