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Title: Interfacial Reduction-Oxidation Mechanisms Governing Fate and Transport of Contaminants in the Vadose Zone

Abstract

The mobility of many contaminants is redox sensitive and thus related to the reduction oxidation characteristics of the environment. Immobilization of certain contaminants (e.g., chromium, uranium, and technetium) can be achieved by reducing the contaminant. One remediation approach to achieving this is the application of diluted hydrogen sulfide gas mixtures, which may have particular value in vadose zone applications. Previous work has shown this approach to be viable for Cr(VI) remediation of soil waste sites. The primary objective of the current research is to assess the potential of in situ gaseous treatment to the immobilization of U(VI) and Tc(VII). This work also addresses basic science aspects of understanding the redox-related aspects of the mobility of these contaminants in the natural environment, thus providing a mechanistic-based understanding needed to successfully achieve remediation.

Authors:
; ; ;
Publication Date:
Research Org.:
Pacific Northwest National Laboratory (PNNL), Richland, WA; University of Missouri, CO; Illinois Institute of Technology, Chicago, IL
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
895721
Report Number(s):
ERSD-90100-2006
R&D Project: ERSD 90100; TRN: US0700517
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
12 MANAGEMENT OF RADIOACTIVE WASTES, AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES; 54 ENVIRONMENTAL SCIENCES; 38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY; CHROMIUM; HYDROGEN SULFIDES; MIXTURES; OXIDATION; SOILS; TECHNETIUM; TRANSPORT; URANIUM; WASTES

Citation Formats

Thornton, Edward C., Baolin Deng, Jurisson, Silvia Sabine, and Terry, Jeff. Interfacial Reduction-Oxidation Mechanisms Governing Fate and Transport of Contaminants in the Vadose Zone. United States: N. p., 2006. Web. doi:10.2172/895721.
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Thornton, Edward C., Baolin Deng, Jurisson, Silvia Sabine, & Terry, Jeff. Interfacial Reduction-Oxidation Mechanisms Governing Fate and Transport of Contaminants in the Vadose Zone. United States. doi:10.2172/895721.
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Thornton, Edward C., Baolin Deng, Jurisson, Silvia Sabine, and Terry, Jeff. Thu . "Interfacial Reduction-Oxidation Mechanisms Governing Fate and Transport of Contaminants in the Vadose Zone". United States. doi:10.2172/895721. https://www.osti.gov/servlets/purl/895721.
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@article{osti_895721,
title = {Interfacial Reduction-Oxidation Mechanisms Governing Fate and Transport of Contaminants in the Vadose Zone},
author = {Thornton, Edward C. and Baolin Deng and Jurisson, Silvia Sabine and Terry, Jeff},
abstractNote = {The mobility of many contaminants is redox sensitive and thus related to the reduction oxidation characteristics of the environment. Immobilization of certain contaminants (e.g., chromium, uranium, and technetium) can be achieved by reducing the contaminant. One remediation approach to achieving this is the application of diluted hydrogen sulfide gas mixtures, which may have particular value in vadose zone applications. Previous work has shown this approach to be viable for Cr(VI) remediation of soil waste sites. The primary objective of the current research is to assess the potential of in situ gaseous treatment to the immobilization of U(VI) and Tc(VII). This work also addresses basic science aspects of understanding the redox-related aspects of the mobility of these contaminants in the natural environment, thus providing a mechanistic-based understanding needed to successfully achieve remediation.},
doi = {10.2172/895721},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Thu Jun 01 00:00:00 EDT 2006},
month = {Thu Jun 01 00:00:00 EDT 2006}
}
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DOI:  10.2172/895721
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  • ; ; ; ...
    Immobilization of toxic and radioactive metals in the vadose zone by In Situ Gaseous Reduction (ISGR) using hydrogen sulfide (H2S) is a promising technology for soil remediation. Earlier laboratory and field studies have shown that Cr(VI) can be effectively immobilized by treatment with dilute gaseous H2S. The objective of this project is to characterize the interactions among H2S, the metal contaminants, and soil components. Understanding these interactions is needed to assess the long-term effectiveness of the technology and to optimize the remediation system.

  • ; ; ; ...
    Immobilization of toxic and radioactive metals (e.g., Cr, Tc, and U) in the vadose zone by in situ gaseous reduction using hydrogen sulfide (H2S) is a promising technology the U.S. Department of Energy (DOE) is developing for soil remediation. Earlier laboratory studies have shown that Cr(VI) in a number of soil samples can be effectively immobilized by treatment with dilute gaseous H2S. A field test has also been completed that resulted in 70% immobilization of Cr(VI). The objective of this project is to characterize the interactions among H2S, the metal contaminants, and soil components. Understanding these interactions is needed tomore » assess the long-term effectiveness of the technology and to optimize the remediation system.« less

  • ; ; ; ...
    Immobilization of toxic and radioactive metals (e.g., Cr, Tc, and U) in the vadose zone by In Situ Gaseous Reduction (ISGR) using hydrogen sulfide (H2S) is a promising technology for soil remediation. Earlier laboratory and field studies have shown that Cr(VI) can be effectively immobilized by treatment with dilute gaseous H2S. The objective of this project is to characterize the interactions among H2S, the metal contaminants, and soil components. Understanding these interactions is needed to assess the long-term effectiveness of the technology and to optimize the remediation system. Proposed research tasks include: (A) Evaluation of the potential catalytic effect ofmore » mineral surfaces on the rate of Cr(VI) reduction by H2S and the rate of H2S oxidation by air; (B) Identification of the reactions of soil minerals with H2S and determination of associated reaction rates; (C) Evaluation of the role of soil water chemistry on the reduction of Cr(VI) by H2S; (D) Assessment of the reductive buffering capacity of H2S reduced soil and the potential for emplacement of long-term vadose zone reactive barriers; (E) Evaluation of the potential for immobilization of Tc and U in the vadose zone by reduction and an assessment of the potential for remobilization by subsequent reoxidation. Through a collaborative effort in the last three years, Tasks A, B, C, and E have been completed, resulting in a much improved understanding of reaction kinetics and mechanisms involved in the Cr(VI)-H2S-O2-Soil System and the treatability for Tc and U. Research on Task C will continue in the one-year period of no-cost extension granted to this project. The result will be submitted to the Department of Energy by October 2003 as a supplement to this report.« less

  • ; ; ; ...
    Immobilization of toxic and radioactive metals (e.g., Cr, Tc, and U) in the vadose zone by the In Situ Gaseous Reduction (ISGR) using hydrogen sulfide (H2S) is a promising technology for soil remediation. Earlier laboratory studies have shown that Cr(VI) in soil samples can be effectively immobilized by treatment with dilute gaseous H2S. A field test completed in 1999 at White Sand Missile Range, New Mexico, has shown a 70% immobilization of Cr(VI). The objective of this EMSP project is to characterize the interactions among H2S, the metal contaminants, and soil components. Understanding these interactions is needed to optimize themore » remediation system and to assess the long-term effectiveness of the technology. Proposed research tasks included: (A) Evaluation of the potential catalytic effect of mineral surfaces on the rate of Cr(VI) reduction by H2S and the rate of H2S oxidation by air; (B) Identification of the reactions of soil minerals with H2S and determination of associated reaction rates; (C) Evaluation of the role of soil water chemistry on the reduction of Cr(VI) by H2S; (D) Assessment of the reductive buffering capacity of H2S-reduced soil and the potential for emplacement of long-term vadose zone reactive barriers; and (E) Evaluation of the potential for immobilization of Tc and U in the vadose zone by reduction and an assessment of the potential for remobilization by subsequent reoxidation.« less

  • Many soil contamination sites at Department of Energy installations contain radionuclides and toxic metals such as technetium (Tc), uranium (U) and chromium (Cr). In Situ Gaseous Reduction (ISGR) using dilute hydrogen sulfide (H2S) as reductant is a technology uniquely suitable for the vadose zone soil remediation to reduce and immobilize these contaminants. It is conceivable that the ISGR approach can be applied either to immobilize pre-existing contaminants or to create a reductive permeable reactive barrier (PRB) through hydrogen sulfide gas treatment of soils for contaminant interception. This project aims to improve our understanding of the complex interactions among the contaminantsmore » (U and Tc), H2S, and various soil constituents. The collaborative effort involving the University of Missouri-Columbia, Pacific Northwest National Laboratory, and Illinois Institute of Technology will provide the knowledge needed to further develop and optimize the ISGR technology. Specific research tasks include: (a) examine the reduction kinetics of Tc(VII) and U(VI) by H2S; (b) measure the reduction kinetics of Tc(VII) and U(VI) by iron sulfides; (c) characterize the speciation of immobilized Tc and U and investigate the immobilization mechanisms; (d) assess the long-term stability of the contaminants immobilized by the ISGR treatment; and (e) validate the pure phase experimental results under natural soil conditions.« less