Advanced TALSPEAK Separations Using a Malonate Buffer System

Lapka, Joseph L.; Nash, Kenneth L.

doi:10.1080/07366299.2015.1012878

Cited by 17 publications

(16 citation statements)

References 27 publications

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“…Separation factors above 100 are seen at pH2.5-4.0; they are apparently nearly independent of malonate concentration. 5 There was no evidence of any tendency to form a second organic phase in any of these samples. Separations performed with HEDTA and HEH(EHP) in this buffer system exhibit fast phase transfer kinetics at lower pH values, while producing a relatively flat pH dependence of the distribution ratios (pH = 2.5-4.0) in studies with both trace metals and a highly metal loaded organic phase.…”

Section: Stagementioning

confidence: 76%

“…Ln 3+ + DTPA 5 In this hypothetical reaction sequence, the first rate limiting process (reaction 9) is the release of the lanthanide cation from the thermodynamically stable Ln(DTPA) 2-; this reaction is typically accompanied by rapid recombination reaction (reaction 10) and diffusion-controlled protonation . By increasing the lactate ion concentration a decrease in the rate of complexation is observed.…”

Section: Subtask 1d Aqueous Complexation Kinetics In Conventional Tamentioning

confidence: 99%

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Advanced Aqueous Separation Systems for Actinide Partitioning

Nash

Martin

Lumetta

2015

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Section: Stagementioning

confidence: 76%

Section: Subtask 1d Aqueous Complexation Kinetics In Conventional Tamentioning

confidence: 99%

Advanced Aqueous Separation Systems for Actinide Partitioning

Nash

Martin

Lumetta

2015

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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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“…Malonate is a more effective buffer than lactate at high acidities and has been tested as an alternative to lactate by Lapka and Nash. 9 They used NaNO 3 as the background electrolyte in the aqueous phase to maintain a constant ionic strength of 1 mol dm −3 and employed N-(hydroxyethyl)ethylenediaminetriacetic acid (HEDTA) and 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (HEH[EHP]) as the complexing agent and extractant, respectively. In this system, the extraction of lanthanide ions was relatively invariant with pH.…”

Section: Introductionmentioning

confidence: 99%

Ion Interaction Models and Measurements of Eu³⁺ Complexation: DTPA in Aqueous Solutions at 25 °C Containing 1:1 Na⁺ Salts and Malonate pH Buffer

Clegg

Zalupski

2016

Ind. Eng. Chem. Res.

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The separation of lanthanides from actinides in the TALSPEAK liquid−liquid distribution process is accomplished using an aminopolycarboxylate complexing agent, for example diethylenetriamine-N,N,N′,N″,N″-pentaacetic acid (DTPA,, in a low pH buffered aqueous phase in contact with an organic phase containing an extractant such as di(2-ethylhexyl)phosphoric acid (HDEHP,. Literature measurements show that the partitioning of lanthanides to the organic phase falls with rising pH whereas thermodynamic equilibrium models suggest that, at pH above approximately 3.5, the partitioning should increase. In this study, the partitioning of Eu 3+ between an aqueous phase (with NaNO 3 background electrolyte, malonate buffer, and DTPA complexing agent), and an organic phase (HDEHP in ndodecane) is measured from pH 2 to 4.5 and for ionic strengths from 0.25 to 1.0 mol kg −1 . The measurements include systems with reduced (by 10×) concentrations of buffer, DTPA, and Eu 3+ . A Pitzer activity coefficient model of the aqueous mixture is developed based upon available osmotic and activity coefficient data, and stoichiometric equilibrium constants in different 1:1 electrolyte media over a range of ionic strengths. This enables the DTPA and buffer speciation, and complexation of Eu 3+ by both DTPA and malonate, to be calculated for different solution compositions and pH. The measured distribution coefficients are consistent with model predictions up to pH 3.5 and, below this pH, vary little with ionic strength. At higher pH, the distribution coefficients at different ionic strengths deviate both from the model and each other, consistent with other reactions occurring in the organic phase than the simple exchange of lanthanide and H + embodied in the TALSPEAK phase transfer reaction.

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Advanced TALSPEAK Separations Using a Malonate Buffer System

Cited by 17 publications

References 27 publications

Advanced Aqueous Separation Systems for Actinide Partitioning

Advanced Aqueous Separation Systems for Actinide Partitioning

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

Ion Interaction Models and Measurements of Eu³⁺ Complexation: DTPA in Aqueous Solutions at 25 °C Containing 1:1 Na⁺ Salts and Malonate pH Buffer

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Advanced TALSPEAK Separations Using a Malonate Buffer System

Cited by 17 publications

References 27 publications

Advanced Aqueous Separation Systems for Actinide Partitioning

Advanced Aqueous Separation Systems for Actinide Partitioning

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

Ion Interaction Models and Measurements of Eu3+ Complexation: DTPA in Aqueous Solutions at 25 °C Containing 1:1 Na+ Salts and Malonate pH Buffer

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Ion Interaction Models and Measurements of Eu³⁺ Complexation: DTPA in Aqueous Solutions at 25 °C Containing 1:1 Na⁺ Salts and Malonate pH Buffer