Electrochemistry and Spectroelectrochemistry of Europium(III) Chloride in 3LiCl–2KCl from 643 to 1123 K

Schroll, Cynthia A.; Chatterjee, Sayandev; Levitskaia, Tatiana G.; Heineman, William R.; Bryan, Samuel A.

doi:10.1021/ac402518p

Cited by 35 publications

(45 citation statements)

References 53 publications

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“…It can be seen from the graph that the redox potentials in the LiCl -RbCl and 3 LiCl -2 CsCl are similar at all temperatures, but that the redox potential in 3 LiCl -NaCl is shifted to more positive potentials. Also, in each melt there is a similar positive shift in the redox potential as the temperature increases and the slopes are 5.1 × 10 29 47 × 10 −4 V K −1 (LiCl -RbCl), and 4.8 × 10…”

Section: Resultsmentioning

confidence: 75%

“…The differential pulse voltammograms were recorded using a 2 mV step, 25 mV pulse and a 0.1 s pulse time. Figure 1A shows the voltammograms for europium(III) 29 LiCl -RbCl, and 3 LiCl -2 CsCl, respectively, in the temperature range from 673 K to 1073 K. The number of electrons transferred was calculated using the width at half height for the reduction peak according to:…”

Section: Resultsmentioning

confidence: 99%

“…The observed trends in diffusion coefficient data are based on the "hopping" mechanism of diffusion through ionic media. This work expands our concerted effort to systematically advance methods for quantitative electrochemical and spectroscopic measurement of lanthanides [29][30][31][32] and actinides within pyroprocessing 29-31 and other nuclear fuel reprocessing flowsheet applications including aqueous separation and detection of lanthanide and transition metal fission products. …”

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confidence: 88%

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Electrochemistry of Europium(III) Chloride in 3 LiCl – NaCl, 3 LiCl – 2 KCl, LiCl – RbCl, and 3 LiCl – 2 CsCl Eutectics at Various Temperatures

Schroll

Chatterjee

Levitskaia

et al. 2017

J. Electrochem. Soc.

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Here we report the effect of changing the eutectic melt composition on the electrochemical properties of europium(III) chloride under pyroprocessing conditions. Stoichiometry of electron-transfer, redox potentials and diffusion coefficients were determined using various electrochemical and spectroelectrochemical techniques in four different eutectic mixtures (3 LiCl -NaCl, 3 LiCl -2 KCl, LiCl -RbCl, and 3 LiCl -2 CsCl) while varying the temperature of the melt. It was determined that Eu 3+ undergoes a one electron reduction to Eu 2+ in each melt at all temperatures evaluated. Within each of the melts a positive shift in the redox potential as well as an increase in the diffusion coefficient for Eu 3+ was observed as the temperature increased. Also observed was a positive shift in the redox potential and increase in the diffusion coefficient for Eu 3+ as the weighted average of the cationic radii the melt composition decreased. Pyroprocessing is one of the newest techniques for spent nuclear fuel reprocessing in which the separation is accomplished electrochemically in molten salt media at temperatures of >500• C. 1-3 Some of the advantages of pyroprocessing over the more traditional liquidliquid extraction techniques are that there is no organic solvent that is susceptible to radiolysis, 4,5 lack of pure plutonium product which provides less likelihood for proliferation, 6 generation of the U-Pu alloy product is ready for immediate fabrication into new fuel rods 7 and the ability to do a group separation of all actinides.8 There are also engineering related advantages such as amenability to scaling to the needs of the facility 9 and making the refinement vessel more compact. 10,11The most important information needed to understand pyroprocessing is accurate thermodynamic data for each of the analytes that may be found in used nuclear fuel in each of the possible eutectic melt compositions. We have chosen to investigate europium(III) chloride because it is a non-radioactive analog to the actinides which makes it safer to work with, it has the least negative redox potential of the lanthanides, and it undergoes a change in its absorption spectrum when it is reduced from Eu 3+ to Eu 2+ . 12 Prior research has been performed using europium(III) chloride and evaluating its thermodynamic properties in different melts, such as LiCl, 13 In this work we systematically evaluated the redox potentials and diffusion coefficients for europium(III) chloride using differential pulse voltammetry and cyclic voltammetry in three different eutectic salt compositions over a range of temperatures. The experiments were performed from 673 K to 1173 K in 3 LiCl -NaCl, LiCl -RbCl and 3 LiCl -2 CsCl. This data along with the results from our previous * Electrochemical Society Member.z E-mail: heinemwr@ucmail.uc.edu; sam.bryan@pnl.gov reports (Electrochemistry of Europium in 3 LiCl -2 KCl from 643 to 1123 K 29 and Spectroelectrochemistry of Europium in 3 LiCl -NaCl, 3 LiCl -2 KCl, LiCl -RbCl, and 3 LiCl −2 CsCl at 873 K 30 ) were analyzed ...

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Section: Resultsmentioning

confidence: 75%

Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 88%

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Electrochemistry of Europium(III) Chloride in 3 LiCl – NaCl, 3 LiCl – 2 KCl, LiCl – RbCl, and 3 LiCl – 2 CsCl Eutectics at Various Temperatures

Schroll

Chatterjee

Levitskaia

et al. 2017

J. Electrochem. Soc.

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“…It would also be desirable to develop such a technique into an online monitoring system. The literature on MS online monitoring can be divided into two major groups: spectrophotometric methods [8][9][10][11] and electrochemical methods [12][13][14][15][16][17] . Spectrophotometric methods suffer from the significant disadvantages of requiring the engineering of sampling access points and being limited to those species containing optically distinct chromophores.…”

Section: Introductionmentioning

confidence: 99%

Enhanced Electroanalysis in Lithium Potassium Eutectic (LKE) Using Microfabricated Square Microelectrodes

et al. 2014

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Molten salts (MSs) are an attractive medium for chemical and electrochemical processing and as a result there is demand for MS-compatible analysis technologies. However, MSs containing redox species present a challenging environment in which to perform analytical measurements because of their corrosive nature, significant thermal convection and the high temperatures involved. This paper outlines the fabrication and characterization of microfabricated square microelectrodes (MSMs) designed for electrochemical analysis in MS systems. Their design enables precise control over electrode dimension, the minimization of stress because of differential thermal expansion through design for high temperature operation, and the minimization of corrosive attack through effective insulation. The exemplar MS system used for characterization was lithium chloride/potassium chloride eutectic (LKE), which has potential applications in pyrochemical nuclear fuel reprocessing, metal refining, molten salt batteries and electric power cells. The observed responses for a range of redox ions between 400 and 500 °C (673 and 773 K) were quantitative and typical of microelectrodes. MSMs also showed the reduced iR drop, steady-state diffusion-limited response, and reduced sensitivity to convection seen for microelectrodes under ambient conditions and expected for these electrodes in comparison to macroelectrodes. Diffusion coefficients were obtained in close agreement with literature values, more readily and at greater precision and accuracy than both macroelectrode and previous microelectrode measurements. The feasibility of extracting individual physical parameters from mixtures of redox species (as required in reprocessing) and of the prolonged measurement required for online monitoring was also demonstrated. Together, this demonstrates that MSMs provide enhanced electrode devices widely applicable to the characterization of redox species in a range of MS systems.

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“…The concentration ratio of Eu 2C to Eu 3C was measured as 0.4, and this reduction was estimated to be caused by the oxidation of Cl ¡ to Cl 2 . Electrochemistry and spectro-electrochemistry of Eu(III)Cl 3 in 3LiCl-2KCl from 370 to 850 C was studied by Schroll et al (38). Because the combination of the two techniques can induce various oxidation states of the samples, it is possible to measure the absorbance of the electrochemically prepared species.…”

Section: Spectroscopic Studies Of Lanthanides Ion 661mentioning

confidence: 99%

Spectroscopic Studies of Lanthanides Ion in High-Temperature Molten Salt

Song

Yeon

2015

Applied Spectroscopy Reviews

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Spectroscopic studies for lanthanide elements in molten salt media performed using absorption, fluorescence, infrared, Raman, electron spin resonance spectroscopy (EPR), and M€ ossbaur spectroscopy were reviewed in an effort to understand the effect of structural change and chemical behavior of lanthanides on the temperature increase and the matrix change. The absorption spectroscopic studies revealed electronic energy levels of the transitions with the general structural information of the lanthanide elements, whereas the laser-induced fluorescence studies revealed more detailed information on lanthanide elements such as the lifetime behavior, structural changes, and hypersensitive transition. Infrared and Raman spectroscopy also provided structural details of molecule containing lanthanides, and the EPR and M€ ossbaur spectroscopy provided supporting information for the spontaneous reduction of trivalent lanthanides, such as Eu(III). The recent development of X-ray spectroscopy such as extended X-ray absorption fine structure (EXAFS) also provided detailed information for lanthanide halide in a molten salt medium. The characteristics of f-d as well as f-f transitions of the lanthanide elements were reviewed and the structural changes depending on the media, lanthanides element, and temperature were discussed in detail.

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Electrochemistry and Spectroelectrochemistry of Europium(III) Chloride in 3LiCl–2KCl from 643 to 1123 K

Cited by 35 publications

References 53 publications

Electrochemistry of Europium(III) Chloride in 3 LiCl – NaCl, 3 LiCl – 2 KCl, LiCl – RbCl, and 3 LiCl – 2 CsCl Eutectics at Various Temperatures

Electrochemistry of Europium(III) Chloride in 3 LiCl – NaCl, 3 LiCl – 2 KCl, LiCl – RbCl, and 3 LiCl – 2 CsCl Eutectics at Various Temperatures

Enhanced Electroanalysis in Lithium Potassium Eutectic (LKE) Using Microfabricated Square Microelectrodes

Spectroscopic Studies of Lanthanides Ion in High-Temperature Molten Salt

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