The role of carboxylic acids in TALSQuEAK separations

Braley, Jenifer C.; Carter, Jennifer C.; Sinkov, Sergey I.; Nash, K.L.; Lumetta, Gregg J.

doi:10.1080/00958972.2012.704551

Cited by 31 publications

(36 citation statements)

References 35 publications

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“…For example, there has been substantial development of plutonium separations chemistry. 3,4,[5][6][7][8]9,10 Combined with recent advances in separations science 11,12,13,14,15,16,17,[18][19][20]21,22 and chromatography technologies 23,24,25,26,27,28,29 i.e. commercialization of specialty resins -it is now relatively straightforward to recover/recycle plutonium from previous experiments.…”

Section: Introductionmentioning

confidence: 99%

Advances in containment methods and plutonium recovery strategies that led to the structural characterization of plutonium(IV) tetrachloride tris-diphenylsulfoxide, PuCl4(OSPh2)3

et al. 2017

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In an attempt to further advance the understanding of plutonium coordination chemistry, we report a robust method for recycling and obtaining plutonium aqueous stock 2 solutions that can be used as a convenient starting material in plutonium synthesis. This approach was used to prepare and characterize plutonium(IV) tetrachloride trisdiphenylsulfoxide, PuCl 4 (OSPh 2) 3 , by single crystal X-ray diffraction. The PuCl 4 (OSPh 2) 3 compound represents a rare example of a 7 coordinate plutonium(IV) complex. Structural characterization of PuCl 4 (OSPh 2) 3 by X-ray diffraction utilized a new containment method for radioactive crystals. The procedure makes use of epoxy, polyimide loops, and a polyester sheath to provide a robust method for safely containing and easily handling radioactive samples. The described procedure is more user friendly than traditional containment methods that employ fragile quartz capillary tubes. Additionally, moving to polyester, instead of quartz, lowers the background scattering from the heavier silicon atoms.

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Section: Introductionmentioning

confidence: 99%

Advances in containment methods and plutonium recovery strategies that led to the structural characterization of plutonium(IV) tetrachloride tris-diphenylsulfoxide, PuCl4(OSPh2)3

et al. 2017

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“…An alternative was sought to overcome these limitations of TALSPEAK. [15][16][17][18][19][20][21] A new chemical system was investigated in-depth based on the use of a combination of 2ethylhexylphosphonic acid mono-2-ethylhexyl ester (HEH [EHP] or PC88A) and N- (2-hydroxyethyl)ethylenediamine-N,N',N'-triacetic acid (HEDTA) in a citrate-buffered system (Figure 1). Optimal process conditions were found for 1.0 mol/L HEH [EHP] in n-dodecane as the solvent, and a feed solution containing the metal ions and 0.125 mol/L HEDTA and 0.6 mol/L citrate at pH 2.6.…”

Section: Introductionmentioning

confidence: 99%

An Advanced TALSPEAK Concept for Separating Minor Actinides. Part 2. Flowsheet Test with Actinide-spiked Simulant

Wilden

Lumetta

Sadowski

et al. 2017

Solvent Extraction and Ion Exchange

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An Advanced TALSPEAK counter-current flowsheet test was demonstrated using a simulated feed spiked with radionuclides in annular centrifugal contactors. A solvent comprising 2ethylhexylphosphonic acid mono-2-ethylhexyl ester (HEH[EHP] or PC88A) in n-dodecane was used to extract trivalent lanthanides away from the trivalent actinides Am 3+ and Cm 3+ , which were preferentially complexed in a citrate buffered aqueous phase with N-(2hydroxyethyl)ethylenediamine-N,N',N'-triacetic acid (HEDTA). In a 24-stages demonstration test the trivalent actinides were efficiently separated from the trivalent lanthanides with decontamination factors >1,000, demonstrating the excellent performance of the chemical system. Clean actinide and lanthanide product fractions and spent solvent with very low contaminations were obtained. The results of the process test are presented and discussed.

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“…The efficiency of the TALSPEAK process is affected by a few drawbacks including the less predictable pH dependence, the significant partitioning of Na + , lactic acid, and water into the organic phase, and the slow extraction kinetics [4,5]. Recently, a modified TALSPEAK process was proposed in which HDEHP is replaced by its phosphonic acid analog, 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester acid (HEH [EHP]), as the extractant, and DTPA is replaced by N-(2-hydroxyethyl)ethylenediamine-N,N 0 ,N 0 -triacetic acid (HEDTA, figure 1) as the aqueous hold-back complexant [4].…”

Section: Introductionmentioning

confidence: 99%

“…Recently, a modified TALSPEAK process was proposed in which HDEHP is replaced by its phosphonic acid analog, 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester acid (HEH [EHP]), as the extractant, and DTPA is replaced by N-(2-hydroxyethyl)ethylenediamine-N,N 0 ,N 0 -triacetic acid (HEDTA, figure 1) as the aqueous hold-back complexant [4]. Several improvements were observed with the modified TALSPEAK, including more predictable extraction behavior, faster kinetics, and less dependence on the acidity [5].…”

Section: Introductionmentioning

confidence: 99%

Effect of temperature on the protonation of N-(2-hydroxyethyl)ethylenediamine-N,N′,N′-triacetic acid in aqueous solutions: Potentiometric and calorimetric studies

Zhang

Endrizzi

et al. 2015

The Journal of Chemical Thermodynamics

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a b s t r a c tThe TALSPEAK process (Trivalent Actinide Lanthanide Separations by Phosphorus-reagent Extraction from Aqueous Komplexes) has been demonstrated in several pilot-scale operations to be effective at separating trivalent actinides (An 3+ ) from trivalent lanthanides (Ln 3+ ). However, fundamental studies have revealed undesired aspects of TALSPEAK, such as the significant partitioning of Na + , lactic acid, and water into the organic phase, thermodynamically unpredictable pH dependence, and the slow extraction kinetics. In the modified TALSPEAK process, the combination of the aqueous holdback complexant HEDTA (N-(2-hydroxyethyl)ethylenediamine-N,N 0 ,N 0 -triacetic acid) with the extractant HEH[EHP] (2-ethyl(hexyl) phosphonic acid mono-2-ethylhexyl ester) in the organic phase has been found to exhibit a nearly flat pH dependence between 2.5 and 4.5 and more rapid phase transfer kinetics for the heavier lanthanides. To help understand the speciation of Ln 3+ and An 3+ in the modified TALSPEAK, systematic studies are underway on the thermodynamics of major reactions in the HEDTA system under conditions relevant to the process (e.g., higher temperatures). Thermodynamics of the protonation and complexation of HEDTA with Ln 3+ were studied at variable temperatures. Equilibrium constants and enthalpies were determined by a combination of techniques including potentiometry and calorimetry. This paper presents the protonation constants of HEDTA at T = (25 to 70)°C. The potentiometric titrations have demonstrated that, stepwise, the first two protonation constants decrease and the third one slightly increases with the increase of temperature. This trend is in good agreement with the enthalpy of protonation directly determined by calorimetry. The results of NMR analysis further confirm that the first two protonation reactions occur on the diamine nitrogen atoms, while the third protonation reaction occurs on the oxygen of a carboxylate group. These data, in conjunction with the thermodynamic parameters of Ln 3+ /An 3+ complexes with HEDTA at different temperatures, will help to predict the speciation and temperature-dependent behavior of Ln 3+ /An 3+ in the modified TALSPEAK process.

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The role of carboxylic acids in TALSQuEAK separations

Cited by 31 publications

References 35 publications

Advances in containment methods and plutonium recovery strategies that led to the structural characterization of plutonium(IV) tetrachloride tris-diphenylsulfoxide, PuCl4(OSPh2)3

Advances in containment methods and plutonium recovery strategies that led to the structural characterization of plutonium(IV) tetrachloride tris-diphenylsulfoxide, PuCl4(OSPh2)3

An Advanced TALSPEAK Concept for Separating Minor Actinides. Part 2. Flowsheet Test with Actinide-spiked Simulant

Effect of temperature on the protonation of N-(2-hydroxyethyl)ethylenediamine-N,N′,N′-triacetic acid in aqueous solutions: Potentiometric and calorimetric studies

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