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Title: Reductive Immobilization of Toxic Metals and Radionuclides by Hydrogen Sulfide

Abstract

No abstract prepared.

Authors:
; ; ;
Publication Date:
Research Org.:
University of Missouri-Columbia, MO; Pacific Northwest National Laboratory (PNNL), Richland, WA; Illinois Institute of Technology (IIT), Chicago, IL
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
894367
Report Number(s):
CONF-ERSP2006-19
TRN: US0700154
Resource Type:
Conference
Resource Relation:
Conference: Annual Environmental Remediation Sciences Program PI Meeting, April 3-5, 2006, Warrenton, VA
Country of Publication:
United States
Language:
English
Subject:
38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY; 54 ENVIRONMENTAL SCIENCES; HYDROGEN SULFIDES; RADIOISOTOPES; NUCLEAR CHEMISTRY

Citation Formats

Baolin Deng, Jurisson, Silvia, Thornton, E.C., and Terry, Jeff. Reductive Immobilization of Toxic Metals and Radionuclides by Hydrogen Sulfide. United States: N. p., 2006. Web.
Baolin Deng, Jurisson, Silvia, Thornton, E.C., & Terry, Jeff. Reductive Immobilization of Toxic Metals and Radionuclides by Hydrogen Sulfide. United States.
Baolin Deng, Jurisson, Silvia, Thornton, E.C., and Terry, Jeff. Wed . "Reductive Immobilization of Toxic Metals and Radionuclides by Hydrogen Sulfide". United States. doi:. https://www.osti.gov/servlets/purl/894367.
@article{osti_894367,
title = {Reductive Immobilization of Toxic Metals and Radionuclides by Hydrogen Sulfide},
author = {Baolin Deng and Jurisson, Silvia and Thornton, E.C. and Terry, Jeff},
abstractNote = {No abstract prepared.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Wed Apr 05 00:00:00 EDT 2006},
month = {Wed Apr 05 00:00:00 EDT 2006}
}

Conference:
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  • 'The purpose of the authors research is to provide an improved understanding and predictive capability of the mechanisms that allow metal-reducing bacteria to be effective in the bioremediation of subsurface environments contaminated with toxic metals and radionuclides. The research findings of the work plan will (1) provide new insights into the previously unexplored areas of competing geochemical and microbiological oxidation/reduction reactions that govern the fate and transport of redox sensitive contaminants in subsurface environments and (2) provide basic knowledge to define the optimum conditions for the microbial reduction and concomitant immobilization of toxic metals and radionuclides in the subsurface. Strategiesmore » that use in situ contaminant immobilization can be efficient and cost-effective remediation options. This project will focus on the following specific objectives. Develop an improved understanding of the rates and mechanisms of competing geochemical and microbiological oxidation/reduction reactions that govern the fate and transport of uranium (U), chromium (Cr), and cobalt-EDTA (Co-EDTA) in the subsurface. Quantify the conditions that optimize the microbial reduction of toxic metals and radionuclides for the purpose of contaminant containment and remediation in heterogeneous systems that have competing geochemical oxidation, sorption, and organic ligands.'« less
  • Department of Energy (DOE) facilities within the weapons complex face a daunting challenge of remediating huge below inventories of legacy radioactive and toxic metal waste. More often than not, the scope of the problem is massive, particularly in the high recharge, humid regions east of the Mississippi river, where the off-site migration of contaminants continues to plague soil water, groundwater, and surface water sources. As of 2002, contaminated sites are closing rapidly and many remediation strategies have chosen to leave contaminants in-place. In situ barriers, surface caps, and bioremediation are often the remedial strategies of chose. By choosing to leavemore » contaminants in-place, we must accept the fact that the contaminants will continue to interact with subsurface and surface media. Contaminant interactions with the geosphere are complex and investigating long term changes and interactive processes is imperative to verifying risks. We must be able to understand the consequences of our action or inaction. The focus of this manuscript is to describe recent technical developments for assessing the performance of in situ bioremediation and immobilization of subsurface metals and radionuclides. Research within DOE's NABIR and EMSP programs has been investigating the possibility of using subsurface microorganisms to convert redox sensitive toxic metals and radionuclides (e.g. Cr, U, Tc, Co) into a less soluble, less mobile forms. Much of the research is motivated by the likelihood that subsurface metal-reducing bacteria can be stimulated to effectively alter the redox state of metals and radionuclides so that they are immobilized in situ for long time periods. The approach is difficult, however, since subsurface media and waste constituents are complex with competing electron acceptors and hydrogeological conditions making biostimulation a challenge. Performance assessment of in situ biostimulation strategies is also difficult and typically requires detailed monitoring of coupled hydrological, geochemical/geophysical, and microbial processes. In the following manuscript we will (1) discuss contaminant fate and transport problems in humid regimes, (2) efforts to immobilize metals and radionuclides in situ via bioremediation, and (3) state-of-the-art techniques for assessing the performance of in situ bioreduction and immobilization of metals and radionuclides. These included (a) in situ solution and solid phase monitoring, (b) in situ and laboratory microbial community analysis, (c) noninvasive geophysical methods, and (d) solid phase speciation via high resolution spectroscopy.« less
  • At the D.O.E. Hanford Reservation, accelerated migration of radionuclides has been observed in the vadose zone underlying the tank farms. Our goal is to provide an improved understanding and predictive capability of the coupled hydrogeochemical mechanisms responsible for observed migration. Our approach is to perform a suite of experiments ranging from novel surface interrogation techniques (e.g., XAS) to miscible displacement experiments on disturbed and undisturbed sediments from the Hanford, Plio-Pleistocene and Ringold formations. Results indicate during unsaturated conditions hydrologic processes governing transport are a strong function of sediment layering in the Hanford and Ringold formations. The transport of radionuclides andmore » toxic metals (U, Cr(VI), Cs, Sr and Co) is influenced by reactive geochemical nonequilibrium, sedimentary mineralogy and solution chemistry. This research will provide new insights into how physical and mineralogical heterogeneities (e.g. stratification, pore regime connectivity, mineral composition along flowpaths) influence contaminant retardation and degree of geochemical nonequilibrium during transport.« less
  • Bioremediation stabilizes and reclaims radionuclide or toxic metal-contaminated materials, soils, sediments, or wastes; it then recovers the contaminating radionuclides and metals. Waste materials are stabilized and reduced in volume using anaerobic bacteria; or alternatively, materials are treated with citric acid before bioremediation begins. Photolysis is used after bioremediation to release radionuclides.
  • A process has been developed at Brookhaven National Laboratory (BNL) for the removal of metals and radionuclides from contaminated materials, soils, and waste sites (Figure 1). In this process, citric acid, a naturally occurring organic complexing agent, is used to extract metals such as Ba, Cd, Cr, Ni, Zn, and radionuclides Co, Sr, Th, and U from solid wastes by formation of water soluble, metal-citrate complexes. Citric acid forms different types of complexes with the transition metals and actinides, and may involve formation of a bidentate, tridentate, binuclear, or polynuclear complex species. The extract containing radionuclide/metal complex is then subjectedmore » to microbiological degradation followed by photochemical degradation under aerobic conditions. Several metal citrate complexes are biodegraded and the metals are recovered in a concentrated form with the bacterial biomass. Uranium forms binuclear complex with citric acid and is not biodegraded. The supernatant containing uranium citrate complex is separated and upon exposure to light, undergoes rapid degradation resulting in the formation of an insoluble, stable polymeric form of uranium. Uranium is recovered as a precipitate (uranium trioxide) in a concentrated form for recycling or for appropriate disposal. This treatment process, unlike others which use caustic reagents, does not create additional hazardous wastes for disposal and causes little damage to soil which can then be returned to normal use.« less