17 Matching Results

Search Results

Advanced search parameters have been applied.

Computational Design of Metal Ion Sequestering Agents

Description: Organic ligands that exhibit a high degree of metal ion recognition are essential precursors for developing separation processes and sensors for metal ions. Since the beginning of the nuclear era, much research has focused on discovering ligands that target specific radionuclides. Members of the Group 1A and 2A cations (e.g., Cs, Sr, Ra) and the f-block metals (actinides and lanthanides) are of primary concern to DOE. Although there has been some success in identifying ligand architectures that exhibit a degree of metal ion recognition, the ability to control binding affinity and selectivity remains a significant challenge. The traditional approach for discovering such ligands has involved lengthy programs of organic synthesis and testing that, in the absence of reliable methods for screening compounds before synthesis, have resulted in much wasted research effort. This project seeks to enhance and strengthen the traditional approach through computer-aided design of new and improved host molecules. Accurate electronic structure calculations are coupled with experimental data to provide fundamental information about ligand structure and the nature of metal-donor group interactions (design criteria). This fundamental information then is used in a molecular mechanics model (MM) that helps us rapidly screen proposed ligand architectures and select the best members from a set of potential candidates. By using combinatorial methods, molecule building software has been developed that generates large numbers of candidate architectures for a given set of donor groups. The specific goals of this project are: • further understand the structural and energetic aspects of individual donor group- metal ion interactions and incorporate this information within the MM framework • further develop and evaluate approaches for correlating ligand structure with reactivity toward metal ions, in other words, screening capability • use molecule structure building software to generate large numbers of candidate ligand architectures for given sets of donor groups ...
Date: June 15, 2005
Creator: Hay, Benjamin P. & Rapko, Brian M.
Partner: UNT Libraries Government Documents Department

Computational Design of Metal Ion Sequestering Agents

Description: Organic ligands that exhibit a high degree of metal ion recognition are essential precursors for developing separation processes and sensors for metal ions. Since the beginning of the nuclear era, much research has focused on discovering ligands that target specific radionuclides. Members of the Group 1A and 2A cations (e.g., Cs, Sr, Ra) and the f-block metals (actinides and lanthanides) are of primary concern to DOE. Although there has been some success in identifying ligand architectures that exhibit a degree of metal ion recognition, the ability to control binding affinity and selectivity remains a significant challenge. The traditional approach for discovering such ligands has involved lengthy programs of organic synthesis and testing that, in the absence of reliable methods for screening compounds before synthesis, have resulted in much wasted research effort.
Date: June 1, 2006
Creator: Hay, Benjamin P. & Rapko, Brian M.
Partner: UNT Libraries Government Documents Department

Computational Design of Metal Ion Sequestering Agents

Description: Organic ligands that exhibit a high degree of metal ion recognition are essential precursors for developing separation processes and sensors for metal ions. Since the beginning of the nuclear era, much research has focused on discovering ligands that target specific radionuclides. Members of the Group 1A and 2A cations (e.g., Cs, Sr, Ra) and the f-block metals (actinides and lanthanides) are of primary concern to DOE. Although there has been some success in identifying ligand architectures that exhibit a degree of metal ion recognition, the ability to control binding affinity and selectivity remains a significant challenge. The traditional approach for discovering such ligands has involved lengthy programs of organic synthesis and testing that, in the absence of reliable methods for screening compounds before synthesis, have resulted in much wasted research effort.
Date: June 15, 2005
Creator: Hay, Benjamin P. & Rapko, Brian M.
Partner: UNT Libraries Government Documents Department

Computational Design of Metal Ion Sequestering Agents

Description: Organic ligands that exhibit a high degree of metal ion recognition are essential precursors for developing separation processes and sensors for metal ions. Since the beginning of the nuclear era, much research has focused on discovering ligands that target specific radionuclides. Members of the Group 1A and 2A cations (e.g., Cs, Sr, Ra) and the f-block metals (actinides and lanthanides) are of primary concern to DOE. Although there has been some success in identifying ligand architectures that exhibit a degree of metal ion recognition, the ability to control binding affinity and selectivity remains a significant challenge. The traditional approach for discovering such ligands has involved lengthy programs of organic synthesis and testing that, in the absence of reliable methods for screening compounds before synthesis, have resulted in much wasted research effort. This project seeks to enhance and strengthen the traditional approach through computer-aided design of new and improved host molecules. Accurate electronic structure calculations are coupled with experimental data to provide fundamental information about ligand structure and the nature of metal-donor group interactions (design criteria). This fundamental information then is used in a molecular mechanics model (MM3) that helps us rapidly screen proposed ligand architectures and select the best members from a set of potential candidates. By using combinatorial methods, molecule building software has been developed that generates large numbers of candidate architectures for a given set of donor groups. The specific objectives of this project are: to further understand the structural and energetic aspects of individual donor group-metal ion interactions and incorporate this information within the framework of MM3; to further develop and evaluate approaches for correlating ligand structure with reactivity toward metal ions, in other words, screening capability; to use molecule structure building software to generate large numbers of candidate ligand architectures for given sets of donor groups; ...
Date: June 1, 2000
Creator: Hay, Benjamin P.; Dixon, David A. & Rapko, Brian M.
Partner: UNT Libraries Government Documents Department

Computational Design of Metal Ion Sequestering Agents

Description: Organic ligands that exhibit a high degree of metal ion recognition are essential precursors for developing separation processes and sensors for metal ions. Since the beginning of the nuclear era, much research has focused on discovering ligands that target specific radionuclides. Members of the Group 1A and 2A cations (e.g., Cs, Sr, Ra) and the f-block metals (actinides and lanthanides) are of primary concern to DOE. Although there has been some success in identifying ligand architectures that exhibit a degree of metal ion recognition, the ability to control binding affinity and selectivity remains a significant challenge. The traditional approach for discovering such ligands has involved lengthy programs of organic synthesis and testing that, in the absence of reliable methods for screening compounds before synthesis, have resulted in much wasted research effort. This project seeks to enhance and strengthen the traditional approach through computer-aided design of new and improved host molecules. Accurate electronic structure calculations are coupled with experimental data to provide fundamental information about ligand structure and the nature of metal-donor group interactions (design criteria). This fundamental information then is used in a molecular mechanics model (MM3) that helps us rapidly screen proposed ligand architectures and select the best members from a set of potential candidates. By using combinatorial methods, molecule building software has been developed that generates large numbers of candidate architectures for a given set of donor groups. The specific goals of this project are: (1) further understand the structural and energetic aspects of individual donor group-metal ion interactions and incorporate this information within the MM3 framework; (2) further develop and evaluate approaches for correlating ligand structure with reactivity toward metal ions, in other words, screening capability; (3) use molecule structure building software to generate large numbers of candidate ligand architectures for given sets of donor groups; (4) ...
Date: June 1, 2003
Creator: Hay, Benjamin P.; Dixon, David A. & Rapko, Brian M.
Partner: UNT Libraries Government Documents Department

Computational Design of Metal Ion Sequestering Agents

Description: Organic ligands that exhibit a high degree of metal ion recognition are essential precursors for developing separation processes and sensors for metal ions. Since the beginning of the nuclear era, much research has focused on discovering ligands that target specific radionuclides. Members of the Group 1A and 2A cations (e.g., Cs, Sr, Ra) and the f-block metals (actinides and lanthanides) are of primary concern to the U.S. Department of Energy (DOE). Although there has been some success in identifying ligand architectures that exhibit a degree of metal ion recognition, the ability to control binding affinity and selectivity remains a significant challenge. The traditional approach for discovering such ligands has involved lengthy programs of organic synthesis and testing that, in the absence of reliable methods for screening compounds before synthesis, have resulted in much wasted research effort. This project seeks to enhance and strengthen the traditional approach through computer-aided design of new and improved host molecules. Accurate electronic structure calculations are coupled with experimental data to provide fundamental information about ligand structure and the nature of metal-donor group interactions (design criteria). This fundamental information then is used in a molecular mechanics model (MM3) that helps us rapidly screen proposed ligand architectures and select the best members from a set of potential candidates. By using combinatorial methods, molecule building software has been developed that generates large numbers of candidate architectures for a given set of donor groups. The specific objectives of this project are as follows: (1) Further understand the structural and energetic aspects of individual donor group- metal ion interactions and incorporate this information within the framework of MM3. (2) Further develop and evaluate approaches for correlating ligand structure with reactivity toward metal ions, in other words, screening capability. (3) Use molecule structure building software to generate large numbers of candidate ...
Date: June 1, 2002
Creator: Hay, Benjamin P.; Dixon, David A. & Rapko, Brian M.
Partner: UNT Libraries Government Documents Department

Computational Design of Metal Ion Sequestering Agents

Description: Organic ligands that exhibit a high degree of metal ion recognition are essential precursors for developing separation processes and sensors for metal ions. Since the beginning of the nuclear era, much research has focused on discovering ligands that target specific radionuclides. Members of the Group 1A and 2A cations (e.g., Cs, Sr, Ra) and the f-block metals (actinides and lanthanides) are of primary concern to DOE. Although there has been some success in identifying ligand architectures that exhibit a degree of metal ion recognition, the ability to control binding affinity and selectivity remains a significant challenge. The traditional approach for discovering such ligands has involved lengthy programs of organic synthesis and testing that, in the absence of reliable methods for screening compounds before synthesis, have resulted in much wasted research effort. This project seeks to enhance and strengthen the traditional approach through computer-aided design of new and improved host molecules. Accurate electronic structure calculations are coupled with experimental data to provide fundamental information about ligand structure and the nature of metal-donor group interactions (design criteria). This fundamental information then is used in a molecular mechanics model (MM) that helps us rapidly screen proposed ligand architectures and select the best members from a set of potential candidates. By using combinatorial methods, molecule building software has been developed that generates large numbers of candidate architectures for a given set of donor groups. The specific goals of this project are: further understand the structural and energetic aspects of individual donor group- metal ion interactions and incorporate this information within the MM framework; further develop and evaluate approaches for correlating ligand structure with reactivity toward metal ions, in other words, screening capability; use molecule structure building software to generate large numbers of candidate ligand architectures for given sets of donor groups; and screen candidates ...
Date: June 15, 2004
Creator: Hay, Benjamin P. & Rapko, Brian M.
Partner: UNT Libraries Government Documents Department

Contaminant-Organic Complexes: Their Structure and Energetics in Surface Decontamination Processes

Description: The current debate over possible decontamination processes for U.S. Department of Energy (DOE) facilities is centered on disparate decontamination problems, but the key contaminants (uranium [U], plutonium [Pu], and neptunium [Np]) are universally important. There is no single decontamination technique or agent for all metal surfaces and contaminants with which DOE is faced. However, more innovative agents used alone or in conjunction with traditional processes can increase the potential to reclaim for future use some of these valuable resources or, at the least, decontaminate the metal surfaces to allow disposal as nonradioactive, nonhazardous material. This debate underscores several important issues: (1) regardless of the decontamination scenario, metal (Fe, U, Pu, Np) oxide film removal from the surface is central to decontamination; and (2) simultaneous oxide dissolution and sequestration of actinide contaminants against re-adsorption to a clean metal surface will influence the efficacy of a process or agent and its cost.
Date: June 2002
Creator: Ainsworth, Calvin C.; Hay, Benjamin P.; Traina, Samuel J. & Myneni, Satish C. B.
Partner: UNT Libraries Government Documents Department

Contaminant-Organic Complexes, Their Structure and Energetics in Surface Decontamination Processes

Description: There are many compounds that are naturally occurring biodegradable organic chelates (siderophores) and appear to be more effective at oxide dissolution and actinide complexation than ethylenediaminetetraacetic acid (EDTA) or other organic acids currently used in decontamination processes. These chelates bind hard acids [Fe(III) and actinides(IV)] with extraordinarily high affinities. For example, the binding constant for the siderophore enterobactin with iron is about 1050, and its binding constant for Pu(IV) is estimated to be as high. Hence, this project is investigating the efficacy of using siderophores (or siderophore-like chelates) as decontamination agents of metal surfaces. The specific goals of this project are as follows: (1) To develop an understanding of the interactions between siderophores (and their functional moieties), Fe and actinide oxides, their surface chemical properties that foster their dissolution and the conditions that maximize that dissolution. (2) To develop the computational tools necessary to predict the reactivity of different siderophore functional groups toward oxide dissolution and actinide (IV) solubilization. (3) To identify likely candidate chelates for use in decontamination processes. To meet these objectives, the project combines x-ray absorption spectroscopy (XAS) and computational chemistry to provide basic information on the structure and bonding of siderophore functional groups to metal (Fe and U) oxide specimens common to corrosion products and scales on carbon steel and stainless steel encountered in DOE facilities. The project explores fundamental scientific aspects of oxide mineral surface chemistry and dissolution related to chelate-induced solubilization. The spectroscopic and computational aspects of this project are complemented by macroscopic dissolution and solubilization studies of oxides and associated contaminants. From this combination of molecular, macroscopic, and computational studies, structure-function and structure-reactivity relationships will be developed. These tasks are centered on investigative themes: (1) macroscopic dissolution studies (C. Ainsworth, PNNL), (2) optical spectroscopy (C. Ainsworth [PNNL]), (3) x-ray absorption spectroscopy (XAS) (S. ...
Date: June 2000
Creator: Ainsworth, Calvin C.; Hay, Benjamin P.; Traina, Samuel J. & Myneni, Satish C. B.
Partner: UNT Libraries Government Documents Department

Contaminant-Organic Complexes: Their Structure and Energetics in Surface Decontamination Processes

Description: The current debate over possible decontamination processes for DOE facilities is centered on disparate decontamination problems, but the key contaminants (Thorium [Th],uranium [U], and plutonium [Pu]) are universally important. Innovative agents used alone or in conjunction with traditional processes can increase the potential to reclaim for future use some these valuable resources or at the least decontaminate the metal surfaces to allow disposal as nonradioactive, nonhazardous material. This debate underscores several important issues: (1) regardless of the decontamination scenario, metal (Fe, U, Pu, Np) oxide film removal from the surface is central to decontamination; and (2) simultaneous oxide dissolution and sequestration of actinide contaminants against re-adsorption to a clean metal surface will influence the efficacy of a process or agent and its cost. Current research is investigating the use of microbial siderophores (chelates) to solubilize actinides (i.e., Th, U, Pu) from the surface of Fe oxide surfaces. Continuing research integrates (1) studies of macroscopic dissolution/desorption of common actinide (IV) [Th, U, Pu, Np] solids and species sorbed to and incorporated into Fe oxides, (2) molecular spectroscopy (FTIR, Raman, XAS), to probe the structure and bonding of contaminants, siderophores and their functional moieties, and how these change with the chemical environment, (3) and molecular mechanics and electronic structure calculations to design model siderophore compounds to test and extend the MM3 model.
Date: June 2003
Creator: Ainsworth, Calvin C.; Hay, Benjamin P.; Traina, Samuel J. & Myneni, Satish C. B.
Partner: UNT Libraries Government Documents Department

Contaminant-Organic Complexes, Their Structure and Energetics in Surface Decontamination Processes

Description: There are a wide variety of compounds that are naturally occurring biodegradable organic chelates (siderophores) that appear to be more effective at oxide dissolution and actinide complexation than EDTA or other organic acids now used in decontamination processes. These chelates bind hard acids [Fe(III) and actinides(IV)] with extraordinarily high affinities. For example, the binding constant for the siderophore enterobactin with iron is about 1050, and its binding constant for Pu(IV) is estimated to be as high. Hence, this project is investigating the efficacy of using siderophores (or siderophore-like chelates) as decontamination agents of metal surfaces. The specific goals of this project are as follows: 1. develop an understanding of the surface interaction between siderophores (and their functional moieties), iron, and actinide oxides; their surface chemical properties that foster their dissolution; and the conditions that maximize that dissolution 2. develop the computational tools necessary to predict the reactivity of different siderophore functional groups toward oxide dissolution and actinide(IV) solubilization 3. identify likely candidate chelates for use in decontamination processes. To meet these objectives, the project combines molecular spectroscopy and computational chemistry to provide basic information on the structure and bonding of siderophore functional groups to metal (iron and uranium) oxide specimens common to corrosion products and scales on carbon steel and stainless steel encountered in U.S. Department of Energy (DOE) facilities. The project explores fundamental scientific aspects of oxide mineral surface chemistry and dissolution related to chelate-induced solubilization. The spectroscopic and computational aspects of this project are complemented by macroscopic dissolution and solubilization studies of oxides and associated contaminants. From this combination of molecular, macroscopic, and computational studies, structure-function and structure-reactivity relationships will be developed.
Date: June 1999
Creator: Ainsworth, Calvin C.; Friedrich, Donald M.; Hay, Benjamin P.; Myneni, Satish C. B. & Traina, Samuel J.
Partner: UNT Libraries Government Documents Department

Selective Media for Actinide Collection and Pre-Concentration: Results of FY 2006 Studies

Description: In this work, we have investigated new materials for potential use in automated radiochemical separations. The work can be divided into three primary tasks: (1) synthesis of new ligands with high affinity for actinide ions, (2) evaluation of new materials for actinide ion affinity, and (3) computational design of advanced ligand architectures for highly selective binding of actinide ions. Ligand Synthesis Work was conducted on synthesizing Kl?ui ligand derivatives containing functionalized pendant groups on the cyclopentadienyl ring. The functionalized pendent groups would allow these ligands to be attached to organic and inorganic solid supports. This work focused on synthesizing the compound Na[Cp?Co(PO(OC2H5)2)3], where Cp?= C5H4C(O)OCH3. Synthesizing this compound is feasible, but the method used in FY 2006 produced an impure material. A modified synthetic scheme has been developed and will be pursued in FY 2007. Work was also initiated on synthesizing bicyclic diamides functionalized for binding to polymeric resins or other surfaces. Researchers at the University of Oregon are collaborators in this work. To date, this effort has focused on synthesizing and characterizing a symmetrically substituted bicyclic diamide ligand with the ?COOH functionality. Again, this synthetic effort will continue into FY 2007. Separations Material Evaluation Work was conducted in FY 2006 to provide a more extensive set of data on the selectivity and affinity of extraction chromatography resins prepared by sorption of Kl?ui ligand onto an inert macroreticular polymeric support. Consistent with previous observations, it was found that these materials strongly bind tetravalent actinides. These materials also adsorb trivalent actinides at low nitric acid concentrations, but the affinity for the trivalent actinides decreases with increasing nitric acid concentration. These materials have relatively low affinity for U(VI), but they do sorb U(VI) to a greater extent than Am(III) at [HNO3] > 0.3 M. Preliminary results suggest that the Kl?ui resins can ...
Date: November 17, 2006
Creator: Lumetta, Gregg J.; Addleman, Raymond S.; Hay, Benjamin P.; Hubler, Timothy L.; Levitskaia, Tatiana G.; Sinkov, Sergey I. et al.
Partner: UNT Libraries Government Documents Department

Architectural Design Criteria for F-Block Metal Ion Sequestering Agents

Description: The objective of this project is to provide the means to optimize ligand architecture for f-block metal recognition. Our strategy builds on an innovative and successful molecular modeling approach in developing polyether ligand design criteria for the alkali and alkaline earth cations. The hypothesis underlying this proposal is that differences in metal ion binding with multidentate ligands bearing the same number and type of donor groups are primarily attributable to intramolecular steric factors. We propose quantifying these steric factors through the application of molecular mechanics models. The proposed research involves close integration of theoretical and experimental chemistry. The experimental work entails synthesizing novel ligands and experimentally determining structures and binding constants for metal ion complexation by series of ligands in which architecture is systematically varied. The theoretical work entails using electronic structure calculations to parameterize a molecular mechanics force field for a range of metal ions and ligand types. The resulting molecular mechanics force field will be used to predict low energy structures for unidentate, bidentate, and multidentate ligands and their metal complexes through conformational searches. Results will be analyzed to assess the relative importance of several steric factors including optimal M-L length, optimal geometry at the metal center, optimal geometry at the donor atoms (complementarity), and conformation prior to binding (preorganization). An accurate set of criteria for the design of ligand architecture will be obtained from these results. These criteria will enable researchers to target ligand structures for synthesis and thereby dramatically reduce the time and cost associated with metal-specific ligand development.
Date: June 1, 1999
Creator: Hay, Benjamin P.; Roundhill, David M.; Paine Jr., Robert Treat; Raymond, Kenneth N.; Rogers, Robin D.; Hutchison, James E. et al.
Partner: UNT Libraries Government Documents Department

Next Generation Extractants for Cesium Separation from High-Level Waste: From Fundamental Concepts to Site Implementation

Description: This project seeks a fundamental understanding and major improvement in cesium separation from high-level waste by cesium-selective calixcrown extractants. Systems of particular interest involve novel solvent-extraction systems containing specific members of the calix[4]arene-crown-6 family, alcohol solvating agents, and alkylamines. Questions being addressed pertain to cesium binding strength, extraction selectivity, cesium stripping, and extractant solubility. Enhanced properties in this regard will specifically benefit cleanup projects funded by the USDOE Office of Environmental Management to treat and dispose of high-level radioactive wastes currently stored in underground tanks at the Savannah River Site (SRS), the Hanford site, and the Idaho National Environmental and Engineering Laboratory.1 The most direct beneficiary will be the SRS Salt Processing Project, which has recently identified the Caustic-Side Solvent Extraction (CSSX) process employing a calixcrown as its preferred technology for cesium removal from SRS high-level tank waste.2 This technology owes its development in part to fundamental results obtained in this program.
Date: September 1, 2003
Creator: Moyer, Bruce A; Bazelaire, Eve; Bonnesen, Peter V.; Bryan, Jeffrey C.; Delmau, Laetitia H.; Engle, Nancy L. et al.
Partner: UNT Libraries Government Documents Department

Next Generation Extractants for Cesium Separation from High-Level Waste: From Fundamental Concepts to Site Implementation

Description: This project seeks a fundamental understanding and major improvement in cesium separation from high-level waste by cesium-selective calixcrown extractants. Systems of particular interest involve novel solvent-extraction systems containing specific members of the calix[4]arene-crown-6 family, alcohol solvating agents, and alkylamines. Questions being addressed bear upon cesium binding strength, extraction selectivity, cesium stripping, and extractant solubility. Enhanced properties in this regard will specifically benefit applied projects funded by the USDOE Office of Environmental Management to clean up sites such as the Savannah River Site (SRS), Hanford, and the Idaho National Environmental and Engineering Laboratory. The most direct beneficiary will be the SRS Salt Processing Project, which has recently identified the Caustic-Side Solvent Extraction (CSSX) process employing a calixcrown as its preferred technology for cesium removal from SRS high-level tank waste.
Date: June 1, 2002
Creator: Moyer, Bruce A.; Bonnesen, Peter V.; Bryan, Jeffrey C.; Engle, Nancy L.; Keever, Tamara J.; Levitskaia, Tatiana G. et al.
Partner: UNT Libraries Government Documents Department

Science to Support DOE Site Cleanup: The Pacific Northwest National Laboratory Environmental Management Science Program Awards -- Fiscal Year 2002 Mid-Year Progress Report

Description: Pacific Northwest National Laboratory has been awarded a total of 80 Environmental Management Science Program (EMSP) research grants since the inception of the program in 1996. The Laboratory has collaborated on an additional 14 EMSP awards with funding received through other institution. This report describes how each of the projects awarded in 1999, 2000, and 2001 addresses significant U.S. Department of Energy (DOE) cleanup issues, including those at the Hanford Site. The technical progress made to date in each of these research projects is addressed in the individual project reports included in this document. Projects are under way in three main areas: Tank Waste Remediation, Decontamination and Decommissioning, and Soil and Groundwater Cleanup.
Date: June 11, 2002
Creator: Bredt, Paul R.; Ainsworth, Calvin C.; Brockman, Fred J.; Camaioni, Donald M.; Egorov, Oleg B.; Felmy, Andrew R. et al.
Partner: UNT Libraries Government Documents Department