Mark Dietz - Academia.edu (original) (raw)

Papers by Mark Dietz

Ion Exchange and Solvent Extraction Series, 2009

RSC Advances, 2019

Organic solute partitioning between a hydrophobic deep eutectic solvent and water is directly rel... more Organic solute partitioning between a hydrophobic deep eutectic solvent and water is directly related to the corresponding Pow values.

ACS Symposium Series, 2003

ABSTRACT With few exceptions, research in the field of room-temperature ionic liquids (RTILs) has... more ABSTRACT With few exceptions, research in the field of room-temperature ionic liquids (RTILs) has sought to understand and exploit the " unconventional" aspects of these solvents, among them their wide electrochemical window, ionicity, and near absence of vapor pressure. The resemblance of certain families of RTILs to various well-known liquid ion-exchangers or ionic surfactants, however, raises a question as to the extent to which the behavior of these neoteric solvents can be understood on the basis of the known properties of these more conventional compounds. In this report, we examine this question as it relates to the development of novel, nanostructured media comprising ionic liquids and RTIL-based methods for metal ion separation and preconcentration. The results presented demonstrate that in certain respects, RTILs can be regarded as conventional chemical reagents.

ACS Symposium Series, 2005

The rational design of ionic liquid-based metal ion separation systems requires either that the i... more The rational design of ionic liquid-based metal ion separation systems requires either that the ion transfer properties of these systems be predictable from the known behavior of conventional organic solvents or that the mechanism(s) of ion transfer be understood at a fundamental level. With this in mind, we have examined the transfer of selected metal ions from acidic aqueous media into a series of N,N'dialkylimidazolium-based room-temperature ionic liquids (RTILs) in the presence of crown ethers, neutral organophosphorus extractants, or β-diketones. The results obtained indicate that although certain aspects of metal ion extraction into RTILs parallel the behavior of conventional solvents, ionic liquids frequently play a more active role in the partitioning process, with ion exchange involving the cationic or anionic constituents of the ionic liquid comprising an important mode of ion transfer. The implications of this observation for the application of ILs as extraction solvents are described.

ACS Symposium Series, 1999

Extraction chromatography provides a simple and effective method for the analytical and preparati... more Extraction chromatography provides a simple and effective method for the analytical and preparative-scale separation of a variety of metal ions. Recent advances in extractant design, particularly the development of extractants capable of metal ion recognition or of strong complex formation in highly acidic media, have significantly improved the utility of the technique. Advances in support design, most notably the introduction of functionalized supports to enhance metal ion retention, promise to yield further improvements. Column instability remains a significant obstacle, however, to the process-scale application of extraction chromatography. Extraction chromatography (EXC) is a type of liquid-liquid chromatography that couples the selectivity of solvent extraction (I) with the multistage character of a-_ _ _ .-. The submitted manuscript has been created by the University of Chicago as operator of Argonne National Laboratory ("Argonne') under Contract No. W-31-109-ENG-38 with the U.S. Department 01 Energy. The U.S. Government retains tor itself. and others acting on its behalf. a paid-up, nonexclusive. irrevocable worldwide license in said article to reproduce, prepare derivative works, distribute copies to the public, and perform publicly and dtsplay publicly, by or on behalf of the Government. DISCLAIMER Thii report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or impIied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any sptcific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, mommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.

The pairing of a Lindqvist or Keggin polyoxometalate (POM) anion with an appropriate tetraalkylph... more The pairing of a Lindqvist or Keggin polyoxometalate (POM) anion with an appropriate tetraalkylphosphonium cation, [R 3 R P] + , has been shown to yield an original family of ionic liquids (POM-ILs), among them salts liquid at or near ambient temperature. The physicochemical properties of several such "inorganic liquids", in particular their thermal properties, suggests the possible application of these compounds as robust, thermally-stable solvents for liquid-liquid extraction. A preliminary evaluation of the potential of POM-ILs in this application is presented.

The purpose of this task is to undertake the design, synthesis, and characterization of the next ... more The purpose of this task is to undertake the design, synthesis, and characterization of the next generation of crown ethers for metal-ion separations applicable to USDOE's environmental needs. Target problems include: Li + ions leaching from burial sites at the Oak Ridge Y-12 Plant; fission products 90 Sr and 137 Cs contaminating high-level tank wastes at Hanford, INEEL, and Savannah River; and radium in wastes at the Niagara Falls Storage Site. Unfortunately, the technologies needed to address these problems either do not exist or exhibit substantial deficiencies. Separation techniques such as solvent extraction and ion exchange promise to play a strong role, especially as enhanced with highly selective crown ethers and calixarenes.

The Journal of Physical Chemistry B, 2011

Nuclear magnetic resonance (NMR) spectroscopy has been used to study hydrogen-bonding interaction... more Nuclear magnetic resonance (NMR) spectroscopy has been used to study hydrogen-bonding interactions between water, associated and dissociated acids (i.e., nitric and methanesulfonic acids), and the constituent ions of several water-immiscible room-temperature ionic liquids (ILs). In chloroform solutions also containing a crown ether (CE), water molecules strongly associate with the IL ions, and there is rapid proton exchange between these bound water molecules and hydronium associated with the CE. In neat ILs, the acids form clusters differing in their degree of association and ionization, and their interactions with the CEs are weak. The CE can either promote proton exchange between different clusters in IL solution when their association is weak or inhibit such exchange when the association is strong. Even strongly hydrophobic ILs are shown to readily extract nitric acid from aqueous solution, typically via the formation of a 1:1:1 {H(3)O(+)•CE}NO(3)(-) complex. In contrast, the extraction of methanesulfonic acid is less extensive and proceeds mainly by IL cation-hydronium ion exchange. The relationship of these protic equilibria to the practical application of hydrophobic ILs (e.g., in spent nuclear fuel reprocessing) is discussed.

The Journal of Physical Chemistry B, 2011

Crown ethers (CEs) are macrocyclic ionophores used for the separation of strontium-90 from acidic... more Crown ethers (CEs) are macrocyclic ionophores used for the separation of strontium-90 from acidic nuclear waste streams. Room temperature ionic liquids (ILs) are presently being considered as replacements for traditional molecular solvents employed in such separations. It is desirable that the extraction efficacy obtained with such solvents should not deteriorate in the strong radiation fields generated by decaying radionuclides. This deterioration will depend on the extent of radiation damage to both the IL solvent and the CE solute. While radiation damage to ILs has been extensively studied, the issue of the radiation stability of crown ethers, particularly in an IL matrix, has not been adequately addressed. With this in mind, we have employed electron paramagnetic resonance (EPR) spectroscopy to study the formation of CE-related radicals in the radiolysis of selected CEs in ILs incorporating aromatic (imidazolium and pyridinium) cations. The crown ethers have been found to yield primarily hydrogen loss radicals, H atoms, and the formyl radical. In the low-dose regime, the relative yield of these radicals increases linearly with the mole fraction of the solute, suggesting negligible transfer of the excitation energy from the solvent to the solute; that is, the solvent has a "radioprotective" effect. The damage to the CE in the loading region of practical interest is relatively low. Under such conditions, the main chemical pathway leading to decreased extraction performance is protonation of the macrocycle. At high radiation doses, sufficient to increase the acidity of the IL solvent significantly, such proton complexes compete with the solvent cations as electron traps. In this regime, the CEs will rapidly degrade as the result of H abstraction from the CE ring by the released H atoms. Thus, the radiation dose to which a CE/IL system is exposed must be maintained at a level sufficiently low to avoid this regime.

The Journal of Physical Chemistry B, 2007

Pairing of a Keggin or Lindqvist polyoxometalate (POM) anion with an appropriate tetraalkylphosph... more Pairing of a Keggin or Lindqvist polyoxometalate (POM) anion with an appropriate tetraalkylphosphonium cation is shown to yield the first members of a new family of ionic liquids (ILs). Detailed characterization of one of them, an ambient-temperature "liquid POM" comprising the Lindqvist salt of the trihexyl(tetradecyl) phosphonium cation, by voltammetry, viscometry, conductimetry, and thermal analysis indicates that it exhibits conductivity and viscosity comparable to those of the one previously described inorganic-organic POM-IL hybrid but with substantially improved thermal stability.

Talanta, 2006

The predominant mode of strontium ion transfer from aqueous nitrate media into a series of 1-fluo... more The predominant mode of strontium ion transfer from aqueous nitrate media into a series of 1-fluoroalkyl-3-methylimidazolium bis[(trifluoromethylsulfonyl)]imides containing dicyclohexano-18-crown-6 (DCH18C6) is shown to shift from cation exchange to strontium nitratocrown ether complex partitioning as the length of the fluoroalkyl substituent is increased. Fluoroalkyl substituents are shown to be only slightly more effective than their non-fluorous analogs at inducing this shift. At the same time, the fluorinated ionic liquids (ILs) yield strontium distribution ratios as much as an order of magnitude lower than the corresponding 1-alkyl-3-methylimidazolium (C n mim +) salts. Fluorous ILs thus appear to offer no compelling advantages over C n mim + ionic liquids as extraction solvents.

Talanta, 2007

Significant solubilization of ostensibly water-immiscible ionic liquids (ILs) in acidic aqueous p... more Significant solubilization of ostensibly water-immiscible ionic liquids (ILs) in acidic aqueous phases is induced by the presence of any of a variety of neutral extractants, the apparent result of the formation of the protonated form of the extractant and its subsequent exchange for the cationic component of the IL. The extent of this solubilization is shown to diminish with increasing hydrophobicity of the IL cation and decreasing extractant basicity. These observations raise concerns as to the viability of ILs as "drop in replacements" for traditional organic solvents in the solvent extraction of metal ions.

Separation Science and Technology, 2011

An approach directed at rapid sequestration and disposal of technetium-99 from UREX (uranium extr... more An approach directed at rapid sequestration and disposal of technetium-99 from UREX (uranium extraction) liquid waste streams is presented. This stream is generated during reprocessing of light-water-reactor spent fuel to recycle the actinides and separate fission products for waste disposal. U and Tc are co-extracted from a nitric acid solution using tri-n-butylphosphate in dodecane, so that Tc(VII) is present in

Separation Science and Technology, 2012

The extraction of trivalent lanthanides from an aqueous phase containing 1 M NaClO4 into the room... more The extraction of trivalent lanthanides from an aqueous phase containing 1 M NaClO4 into the room temperature ionic liquid 1-butyl-3-methylimidazolium nonafluoro-1-butanesulfonate by the β-diketone extractant 2-thenoyltrifluoroacetone (Htta) was studied. Radiotracer distribution, absorption spectroscopy, time-resolved laser-induced fluorescence spectroscopy, and X-ray absorption fine structure measurements point to the extraction of multiple lanthanide species. At low extractant concentrations, fully hydrated aqua cations of the

Reactive and Functional Polymers, 1998

The extraction of alkaline earth cations by xylene solutions of dinonylnaphthalenesulfonic acid (... more The extraction of alkaline earth cations by xylene solutions of dinonylnaphthalenesulfonic acid (HDNNS) from aqueous hydrochloric acid solutions containing various aqueous-soluble unsubstituted crown ether ligands (15-crown-6 (15C5), 18-crown-6 (18C6) and 21-crown-7 (21C7)) has been investigated. The extraction results indicate that the extraction of the larger alkaline earth cations by HDNNS is strongly synergized by the presence of the crown ethers in the aqueous phase. Promising results for intra-Group-IIa cation separations have been obtained with each of the three crown ethers investigated. 2 Separation factors for the radium-calcium couple of at least 10 are obtained under a number of conditions, while the separation factors within the radium-barium-strontium series are much lower. Possible problems in developing an extraction chromatographic resin for radium separation and preconcentration based on the extraction data are discussed.

Journal of the American Chemical Society, 2002

Journal of Radioanalytical and Nuclear Chemistry Articles, 1992

A simple method for the separation and preconeentmtion of radiostrontium from acidic nuclear wast... more A simple method for the separation and preconeentmtion of radiostrontium from acidic nuclear waste solutions forsubsequent determination is described. The method involves passage of the waste solution, acidified to at least 2M with nitric acid, through an extraction chromatographic column consisting of a 1M solution of bis-4,4'(5')[(t-butyl)cyclohexano]-18-crown-6 in 1-octanol sorbed on an inert polymeric substrate, which preferentially retains strontium. The strontium may then be stripped from the column with a small volume of either dilute (s 0.05M) nitric acid or water. Actinides present are removed quantitatively prior to strontium separation by passage of the sample through an actinide-specific extraction chromatographic column.

Journal of Electroanalytical Chemistry, 2004

The solid salts of the 1-ethyl-3-methylimidazolium and the 1-n-pentyl-3-methylimidazolium cations... more The solid salts of the 1-ethyl-3-methylimidazolium and the 1-n-pentyl-3-methylimidazolium cations, abbreviated [C 2 mim] þ and [C 5 mim] þ , respectively, of the Keggin heteropolyanion, a-[PW 12 O 40 ] 3À , were prepared. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) measurements of both [C n mim] 3 [a-PW 12 O 40 ] salts (for n ¼ 2 and 5) were performed in acetonitrile containing either tetra-n-butylammonium hexafluorophosphate, abbreviated TBAPF 6 , or the corresponding [C n mim]BF 4 ionic liquids (ILs) as electrolytes. The results are compared with the corresponding data obtained in the neat [C n mim]BF 4 ILs without addition of other electrolytes. The effects of countercation and supporting electrolyte on the voltammetry of the Keggin ion a-[PW 12 O 40 ] 3À are interpreted as resulting from an amalgamation of isomerization, ion-association, and redox processes. The combination of the unique solvent/electrolyte properties of ILs with the well-known electrochemistry of molecular polyoxometalates (POMs) like the Keggin anion leads to redox behavior that may have impact on the research and technology of catalytic and energystorage phenomena.

Inorganica Chimica Acta, 1997

ABSTRACT

Inorganica Chimica Acta, 2004

Addition of an appropriate concentration of water to either 1-decyl-3-methylimidazolium bromide o... more Addition of an appropriate concentration of water to either 1-decyl-3-methylimidazolium bromide or its nitrate analog is shown to trigger the self-assembly of the ionic liquid (IL) and the concomitant formation of gel (“ionogel”) phases adopting a rich variety of structural motifs. Infrared and 1H nuclear magnetic resonance studies indicate that water addition disrupts hydrogen bonding between the imidazolium ring and

Ion Exchange and Solvent Extraction Series, 2009

RSC Advances, 2019

Organic solute partitioning between a hydrophobic deep eutectic solvent and water is directly rel... more Organic solute partitioning between a hydrophobic deep eutectic solvent and water is directly related to the corresponding Pow values.

ACS Symposium Series, 2003

ABSTRACT With few exceptions, research in the field of room-temperature ionic liquids (RTILs) has... more ABSTRACT With few exceptions, research in the field of room-temperature ionic liquids (RTILs) has sought to understand and exploit the " unconventional" aspects of these solvents, among them their wide electrochemical window, ionicity, and near absence of vapor pressure. The resemblance of certain families of RTILs to various well-known liquid ion-exchangers or ionic surfactants, however, raises a question as to the extent to which the behavior of these neoteric solvents can be understood on the basis of the known properties of these more conventional compounds. In this report, we examine this question as it relates to the development of novel, nanostructured media comprising ionic liquids and RTIL-based methods for metal ion separation and preconcentration. The results presented demonstrate that in certain respects, RTILs can be regarded as conventional chemical reagents.

ACS Symposium Series, 2005

The rational design of ionic liquid-based metal ion separation systems requires either that the i... more The rational design of ionic liquid-based metal ion separation systems requires either that the ion transfer properties of these systems be predictable from the known behavior of conventional organic solvents or that the mechanism(s) of ion transfer be understood at a fundamental level. With this in mind, we have examined the transfer of selected metal ions from acidic aqueous media into a series of N,N'dialkylimidazolium-based room-temperature ionic liquids (RTILs) in the presence of crown ethers, neutral organophosphorus extractants, or β-diketones. The results obtained indicate that although certain aspects of metal ion extraction into RTILs parallel the behavior of conventional solvents, ionic liquids frequently play a more active role in the partitioning process, with ion exchange involving the cationic or anionic constituents of the ionic liquid comprising an important mode of ion transfer. The implications of this observation for the application of ILs as extraction solvents are described.

ACS Symposium Series, 1999

Extraction chromatography provides a simple and effective method for the analytical and preparati... more Extraction chromatography provides a simple and effective method for the analytical and preparative-scale separation of a variety of metal ions. Recent advances in extractant design, particularly the development of extractants capable of metal ion recognition or of strong complex formation in highly acidic media, have significantly improved the utility of the technique. Advances in support design, most notably the introduction of functionalized supports to enhance metal ion retention, promise to yield further improvements. Column instability remains a significant obstacle, however, to the process-scale application of extraction chromatography. Extraction chromatography (EXC) is a type of liquid-liquid chromatography that couples the selectivity of solvent extraction (I) with the multistage character of a-_ _ _ .-. The submitted manuscript has been created by the University of Chicago as operator of Argonne National Laboratory ("Argonne') under Contract No. W-31-109-ENG-38 with the U.S. Department 01 Energy. The U.S. Government retains tor itself. and others acting on its behalf. a paid-up, nonexclusive. irrevocable worldwide license in said article to reproduce, prepare derivative works, distribute copies to the public, and perform publicly and dtsplay publicly, by or on behalf of the Government. DISCLAIMER Thii report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or impIied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any sptcific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, mommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.

The pairing of a Lindqvist or Keggin polyoxometalate (POM) anion with an appropriate tetraalkylph... more The pairing of a Lindqvist or Keggin polyoxometalate (POM) anion with an appropriate tetraalkylphosphonium cation, [R 3 R P] + , has been shown to yield an original family of ionic liquids (POM-ILs), among them salts liquid at or near ambient temperature. The physicochemical properties of several such "inorganic liquids", in particular their thermal properties, suggests the possible application of these compounds as robust, thermally-stable solvents for liquid-liquid extraction. A preliminary evaluation of the potential of POM-ILs in this application is presented.

The purpose of this task is to undertake the design, synthesis, and characterization of the next ... more The purpose of this task is to undertake the design, synthesis, and characterization of the next generation of crown ethers for metal-ion separations applicable to USDOE's environmental needs. Target problems include: Li + ions leaching from burial sites at the Oak Ridge Y-12 Plant; fission products 90 Sr and 137 Cs contaminating high-level tank wastes at Hanford, INEEL, and Savannah River; and radium in wastes at the Niagara Falls Storage Site. Unfortunately, the technologies needed to address these problems either do not exist or exhibit substantial deficiencies. Separation techniques such as solvent extraction and ion exchange promise to play a strong role, especially as enhanced with highly selective crown ethers and calixarenes.

The Journal of Physical Chemistry B, 2011

Nuclear magnetic resonance (NMR) spectroscopy has been used to study hydrogen-bonding interaction... more Nuclear magnetic resonance (NMR) spectroscopy has been used to study hydrogen-bonding interactions between water, associated and dissociated acids (i.e., nitric and methanesulfonic acids), and the constituent ions of several water-immiscible room-temperature ionic liquids (ILs). In chloroform solutions also containing a crown ether (CE), water molecules strongly associate with the IL ions, and there is rapid proton exchange between these bound water molecules and hydronium associated with the CE. In neat ILs, the acids form clusters differing in their degree of association and ionization, and their interactions with the CEs are weak. The CE can either promote proton exchange between different clusters in IL solution when their association is weak or inhibit such exchange when the association is strong. Even strongly hydrophobic ILs are shown to readily extract nitric acid from aqueous solution, typically via the formation of a 1:1:1 {H(3)O(+)•CE}NO(3)(-) complex. In contrast, the extraction of methanesulfonic acid is less extensive and proceeds mainly by IL cation-hydronium ion exchange. The relationship of these protic equilibria to the practical application of hydrophobic ILs (e.g., in spent nuclear fuel reprocessing) is discussed.

The Journal of Physical Chemistry B, 2011

Crown ethers (CEs) are macrocyclic ionophores used for the separation of strontium-90 from acidic... more Crown ethers (CEs) are macrocyclic ionophores used for the separation of strontium-90 from acidic nuclear waste streams. Room temperature ionic liquids (ILs) are presently being considered as replacements for traditional molecular solvents employed in such separations. It is desirable that the extraction efficacy obtained with such solvents should not deteriorate in the strong radiation fields generated by decaying radionuclides. This deterioration will depend on the extent of radiation damage to both the IL solvent and the CE solute. While radiation damage to ILs has been extensively studied, the issue of the radiation stability of crown ethers, particularly in an IL matrix, has not been adequately addressed. With this in mind, we have employed electron paramagnetic resonance (EPR) spectroscopy to study the formation of CE-related radicals in the radiolysis of selected CEs in ILs incorporating aromatic (imidazolium and pyridinium) cations. The crown ethers have been found to yield primarily hydrogen loss radicals, H atoms, and the formyl radical. In the low-dose regime, the relative yield of these radicals increases linearly with the mole fraction of the solute, suggesting negligible transfer of the excitation energy from the solvent to the solute; that is, the solvent has a "radioprotective" effect. The damage to the CE in the loading region of practical interest is relatively low. Under such conditions, the main chemical pathway leading to decreased extraction performance is protonation of the macrocycle. At high radiation doses, sufficient to increase the acidity of the IL solvent significantly, such proton complexes compete with the solvent cations as electron traps. In this regime, the CEs will rapidly degrade as the result of H abstraction from the CE ring by the released H atoms. Thus, the radiation dose to which a CE/IL system is exposed must be maintained at a level sufficiently low to avoid this regime.

The Journal of Physical Chemistry B, 2007

Pairing of a Keggin or Lindqvist polyoxometalate (POM) anion with an appropriate tetraalkylphosph... more Pairing of a Keggin or Lindqvist polyoxometalate (POM) anion with an appropriate tetraalkylphosphonium cation is shown to yield the first members of a new family of ionic liquids (ILs). Detailed characterization of one of them, an ambient-temperature "liquid POM" comprising the Lindqvist salt of the trihexyl(tetradecyl) phosphonium cation, by voltammetry, viscometry, conductimetry, and thermal analysis indicates that it exhibits conductivity and viscosity comparable to those of the one previously described inorganic-organic POM-IL hybrid but with substantially improved thermal stability.

Talanta, 2006

The predominant mode of strontium ion transfer from aqueous nitrate media into a series of 1-fluo... more The predominant mode of strontium ion transfer from aqueous nitrate media into a series of 1-fluoroalkyl-3-methylimidazolium bis[(trifluoromethylsulfonyl)]imides containing dicyclohexano-18-crown-6 (DCH18C6) is shown to shift from cation exchange to strontium nitratocrown ether complex partitioning as the length of the fluoroalkyl substituent is increased. Fluoroalkyl substituents are shown to be only slightly more effective than their non-fluorous analogs at inducing this shift. At the same time, the fluorinated ionic liquids (ILs) yield strontium distribution ratios as much as an order of magnitude lower than the corresponding 1-alkyl-3-methylimidazolium (C n mim +) salts. Fluorous ILs thus appear to offer no compelling advantages over C n mim + ionic liquids as extraction solvents.

Talanta, 2007

Significant solubilization of ostensibly water-immiscible ionic liquids (ILs) in acidic aqueous p... more Significant solubilization of ostensibly water-immiscible ionic liquids (ILs) in acidic aqueous phases is induced by the presence of any of a variety of neutral extractants, the apparent result of the formation of the protonated form of the extractant and its subsequent exchange for the cationic component of the IL. The extent of this solubilization is shown to diminish with increasing hydrophobicity of the IL cation and decreasing extractant basicity. These observations raise concerns as to the viability of ILs as "drop in replacements" for traditional organic solvents in the solvent extraction of metal ions.

Separation Science and Technology, 2011

An approach directed at rapid sequestration and disposal of technetium-99 from UREX (uranium extr... more An approach directed at rapid sequestration and disposal of technetium-99 from UREX (uranium extraction) liquid waste streams is presented. This stream is generated during reprocessing of light-water-reactor spent fuel to recycle the actinides and separate fission products for waste disposal. U and Tc are co-extracted from a nitric acid solution using tri-n-butylphosphate in dodecane, so that Tc(VII) is present in

Separation Science and Technology, 2012

The extraction of trivalent lanthanides from an aqueous phase containing 1 M NaClO4 into the room... more The extraction of trivalent lanthanides from an aqueous phase containing 1 M NaClO4 into the room temperature ionic liquid 1-butyl-3-methylimidazolium nonafluoro-1-butanesulfonate by the β-diketone extractant 2-thenoyltrifluoroacetone (Htta) was studied. Radiotracer distribution, absorption spectroscopy, time-resolved laser-induced fluorescence spectroscopy, and X-ray absorption fine structure measurements point to the extraction of multiple lanthanide species. At low extractant concentrations, fully hydrated aqua cations of the

Reactive and Functional Polymers, 1998

The extraction of alkaline earth cations by xylene solutions of dinonylnaphthalenesulfonic acid (... more The extraction of alkaline earth cations by xylene solutions of dinonylnaphthalenesulfonic acid (HDNNS) from aqueous hydrochloric acid solutions containing various aqueous-soluble unsubstituted crown ether ligands (15-crown-6 (15C5), 18-crown-6 (18C6) and 21-crown-7 (21C7)) has been investigated. The extraction results indicate that the extraction of the larger alkaline earth cations by HDNNS is strongly synergized by the presence of the crown ethers in the aqueous phase. Promising results for intra-Group-IIa cation separations have been obtained with each of the three crown ethers investigated. 2 Separation factors for the radium-calcium couple of at least 10 are obtained under a number of conditions, while the separation factors within the radium-barium-strontium series are much lower. Possible problems in developing an extraction chromatographic resin for radium separation and preconcentration based on the extraction data are discussed.

Journal of the American Chemical Society, 2002

Journal of Radioanalytical and Nuclear Chemistry Articles, 1992

A simple method for the separation and preconeentmtion of radiostrontium from acidic nuclear wast... more A simple method for the separation and preconeentmtion of radiostrontium from acidic nuclear waste solutions forsubsequent determination is described. The method involves passage of the waste solution, acidified to at least 2M with nitric acid, through an extraction chromatographic column consisting of a 1M solution of bis-4,4'(5')[(t-butyl)cyclohexano]-18-crown-6 in 1-octanol sorbed on an inert polymeric substrate, which preferentially retains strontium. The strontium may then be stripped from the column with a small volume of either dilute (s 0.05M) nitric acid or water. Actinides present are removed quantitatively prior to strontium separation by passage of the sample through an actinide-specific extraction chromatographic column.

Journal of Electroanalytical Chemistry, 2004

The solid salts of the 1-ethyl-3-methylimidazolium and the 1-n-pentyl-3-methylimidazolium cations... more The solid salts of the 1-ethyl-3-methylimidazolium and the 1-n-pentyl-3-methylimidazolium cations, abbreviated [C 2 mim] þ and [C 5 mim] þ , respectively, of the Keggin heteropolyanion, a-[PW 12 O 40 ] 3À , were prepared. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) measurements of both [C n mim] 3 [a-PW 12 O 40 ] salts (for n ¼ 2 and 5) were performed in acetonitrile containing either tetra-n-butylammonium hexafluorophosphate, abbreviated TBAPF 6 , or the corresponding [C n mim]BF 4 ionic liquids (ILs) as electrolytes. The results are compared with the corresponding data obtained in the neat [C n mim]BF 4 ILs without addition of other electrolytes. The effects of countercation and supporting electrolyte on the voltammetry of the Keggin ion a-[PW 12 O 40 ] 3À are interpreted as resulting from an amalgamation of isomerization, ion-association, and redox processes. The combination of the unique solvent/electrolyte properties of ILs with the well-known electrochemistry of molecular polyoxometalates (POMs) like the Keggin anion leads to redox behavior that may have impact on the research and technology of catalytic and energystorage phenomena.

Inorganica Chimica Acta, 1997

ABSTRACT

Inorganica Chimica Acta, 2004

Addition of an appropriate concentration of water to either 1-decyl-3-methylimidazolium bromide o... more Addition of an appropriate concentration of water to either 1-decyl-3-methylimidazolium bromide or its nitrate analog is shown to trigger the self-assembly of the ionic liquid (IL) and the concomitant formation of gel (“ionogel”) phases adopting a rich variety of structural motifs. Infrared and 1H nuclear magnetic resonance studies indicate that water addition disrupts hydrogen bonding between the imidazolium ring and