In situ analysis for spontaneous reduction of Eu3+ in LiCl pyroprocessing media at 923 K

Kim, Tack-Jin; Jeong, Yong-Kwang; Kang, Jun‐Gill; Jung, Yongju; Ahn, Do-Hee; Lee, Sang-Kwon

doi:10.1007/s10967-010-0651-0

Cited by 19 publications

(20 citation statements)

References 18 publications

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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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Section: Introductionmentioning

confidence: 99%

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

et al. 2014

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“…[3][4][5][6][7][8] The qualitative and quantitative analysis of reduction of europium from Eu(III) to Eu(II) has been performed in molten alkali chloride salts by electrochemical method, 9,10 absorption spectroscopy, 10 and electron paramagnetic resonance (EPR) technique. 11 Nevertheless, there has been still a relatively large discrepancy of the reducing capacity of europium in chloride molten salts reported in literatures.…”

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confidence: 99%

Reduction of Trivalent Europium in Molten LiCl-KCl Eutectic Observed by In-Situ Laser Spectroscopic Techniques

Kim

Yun

2013

ECS Electrochemistry Letters

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The in-situ quantification for the reduction of Eu(III) was performed in the LiCl-KCl eutectic at various temperatures by time-resolved laser fluorescence spectroscopy (TRLFS) and UV-Vis absorption spectroscopy. From the results of absorption measurement, Eu(III) virtually underwent complete reduction to Eu(II) under the present experimental conditions, while TRLFS revealed a relatively greater reducing power of Eu(III) in the chloride molten eutectic with decreasing its concentration and increasing temperature. However, it was convincingly identified that fluorescence measurements deliver more reliable quantification, compared with the UV-Vis absorption measurements, showing a mutually hindered overlap of absorption bands of Eu(II) and Eu(III).The molten chloride salt is one of the ionic liquid solvents used in the electrorefining and electrowinning of pyrochemical process for recycling used nuclear fuel. Over the past decade, thermodynamic and electrochemical behaviors of actinides and lanthanides in molten chloride salts have been investigated to understand fundamental knowledge and reaction mechanism. 1 An efficient separation of some lanthanides is essential due to their high neutron capture crosssection. Particularly, europium is an attractive and motivating element among lanthanides because of its presence in the multiple oxidation state. Although most lanthanides exist in the trivalent valence state in molten salts, europium can be present in the mixed valence states of Eu(II) and Eu(III) which are likely to cause circulating current in the electrolysis process. 2,3 For that reason, the efficiency of electrolysis during electrorefining and electrowinning process is undoubtedly affected by circulation current arising from alternate reduction and redox reactions at the electrode.The thermodynamic properties of europium ions in molten alkali chloride salt have been studied by electrochemical methods. 3-8 The qualitative and quantitative analysis of reduction of europium from Eu(III) to Eu(II) has been performed in molten alkali chloride salts by electrochemical method, 9,10 absorption spectroscopy, 10 and electron paramagnetic resonance (EPR) technique. 11 Nevertheless, there has been still a relatively large discrepancy of the reducing capacity of europium in chloride molten salts reported in literatures. Kim et al. 10 reported that around 20% of Eu(III) was reduced to Eu(II) at 5.4 × 10 −4 M by absorption spectroscopy and electrochemical analysis in high temperature, and Park et al. 11 observed that approximately 50% of Eu(III) was reduced to Eu(II) measured by EPR technique at room temperature after solidification of molten salt samples. This divergent result requires the reliable technique for in situ quantitative analysis of reduction of trivalent europium. Recently, several groups have measured the fluorescence spectrum of Eu(II) in LiCl-KCl eutectic at various temperatures, 11-13 whereas the fluorescence spectrum of Eu(III) have not been observed in high-temperature LiCl-KCl eutectic. The fluorescen...

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“…Details of the Ag/Ag + electrode are described elsewhere. 19 To determine the characteristic parameters (E 0' , k o , α) for the Eu 3+ /Eu 2+ redox reaction, cyclic voltammograms were taken within a potential range of 0.8 to 0.0 V vs. Ag/Ag + at various scan rates and curve fittings for the CV data were performed using DigiSim software (ver. 3.03, Bioanalytical Systems, Inc.).…”

Section: Methodsmentioning

confidence: 99%

“…9-11 Among many lanthanide species, study on europium species in a molten salt has attracted much attention recently due to its peculiar characteristics. 12,18,19 Lanthanide oxides show very poor solubility in a molten salt media. 18 On the other hand, europium oxide (Eu 2 O 3 ) easily dissolves to form Eu(II) ions even though most of lanthanide ions exist as trivalent states in molten salts.…”

Section: Introductionmentioning

confidence: 99%

Elucidation of Electrode Reaction of EuCl₃in LiCl-KCl Eutectic Melts through CV Curve Analysis

Kim¹,

Jung²,

Kim³

et al. 2011

Bulletin of the Korean Chemical Society

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The electrode reaction of Eu 3+ in a LiCl-KCl eutectic melt has been re-examined using cyclic voltammetry (CV). In this work, for the first time, the kinetic details of a Eu 3+ /Eu 2+ redox system have been completely elucidated, along with the thermodynamic property, through a curve fitting applied to experimental CV data, which were obtained in a wide scan rate range of 0.5 to 10 V/s. The simulated results showed an excellent fit to all experimental CV data simultaneously, even though the curve fittings were performed within a large dynamic range of initial transfer coefficient values, formal potentials, and standard rate constants. As a result, a proper formal potential, transfer coefficient, and standard rate constant for the Eu 3+ /Eu 2+ redox system were successfully extracted using the CV curve fitting.

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In situ analysis for spontaneous reduction of Eu3+ in LiCl pyroprocessing media at 923 K

Cited by 19 publications

References 18 publications

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

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

Reduction of Trivalent Europium in Molten LiCl-KCl Eutectic Observed by In-Situ Laser Spectroscopic Techniques

Elucidation of Electrode Reaction of EuCl₃in LiCl-KCl Eutectic Melts through CV Curve Analysis

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In situ analysis for spontaneous reduction of Eu3+ in LiCl pyroprocessing media at 923 K

Cited by 19 publications

References 18 publications

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

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

Reduction of Trivalent Europium in Molten LiCl-KCl Eutectic Observed by In-Situ Laser Spectroscopic Techniques

Elucidation of Electrode Reaction of EuCl3in LiCl-KCl Eutectic Melts through CV Curve Analysis

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Elucidation of Electrode Reaction of EuCl₃in LiCl-KCl Eutectic Melts through CV Curve Analysis