Electrochemical preparation and spectroelectrochemical study of neptunium chloride complexes in LiCl–KCl eutectic melts

Kim, Dae-Hyeon; Park, Tae‐Hong; Bae, Sang-Eun; Lee, Nari; Kim, Jong-Yun; Cho, Young-Hwan; Yeon, Jei‐Won; Song, Kyuseok

doi:10.1007/s10967-015-4321-0

Cited by 11 publications

(6 citation statements)

References 28 publications

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“…Absorbance recorded during an electrochemical reaction provides information about the concentrations of the absorbing ions that undergo the redox reaction. , The absorbance observed in Figure is proportional to the concentrations of Sm 3+ and Sm 2+ according to Beer’s law. At the potentials applied, the electrochemical reaction involving the Sm cations on a W electrode is as shown below. …”

Section: Resultsmentioning

confidence: 99%

Electrochemical Formation of Divalent Samarium Cation and Its Characteristics in LiCl–KCl Melt

et al. 2018

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The electrochemical reduction of trivalent samarium in a LiCl-KCl eutectic melt produced highly stable divalent samarium, whose electrochemical properties and electronic structure in the molten salt were investigated using cyclic voltammetry, UV-vis absorption spectroscopy, laser-induced emission spectroscopy, and density functional theory (DFT) calculations. Diffusion coefficients of Sm and Sm were electrochemically measured to be 0.92 × 10 and 1.10 × 10 cm/s, respectively, and the standard apparent potential of the Sm couple was estimated to be -0.82 V vs Ag|Ag at 450 °C. The spectroelectrochemical study demonstrated that the redox behavior of the samarium cations obeys the Nernst equation ( E°' = -0.83 V, n = 1) and the trivalent samarium cation was successfully converted to the divalent cation having characteristic absorption bands at 380 and 530 nm with molar absorptivity values of 1470 and 810 M cm, respectively. Density function theory calculations for the divalent samarium complex revealed that the absorption signals originated from the 4f to 4f5d transitions. Additionally, laser-induced emission measurements for the Sm cations in the LiCl-KCl matrix showed that the Sm ion in the LiCl-KCl melt at 450 °C emitted an orange color of fluorescence, whereas a red colored emission was observed from the Sm ion in the solidified LCl-KCl salt at room temperature.

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Section: Resultsmentioning

confidence: 99%

Electrochemical Formation of Divalent Samarium Cation and Its Characteristics in LiCl–KCl Melt

et al. 2018

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“…The spectroelectrochemical method can electrochemically control the oxidation state of a cation; at the same time, spectroscopically monitor the variation of its electronic properties in the LiCl-KCl eutectic melt. 9 Here we investigate the ytterbium ion that can exist in a stable divalent oxidation state in LiCl-KCl. The spectro-electrochemical study of Yb 2+/3+ presents electrochemical and spectroscopic properties for each oxidation state of the ytterbium ion such as the apparent standard potential, diffusion coefficient, electronic states, etc.…”

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confidence: 99%

Investigation of the Electrochemical Behavior of Ytterbium Cations in LiCl-KCl Melt Using Spectro-Electrochemical Methods

Bae

Kim

Lee

et al. 2015

J. Electrochem. Soc.

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Electrochemical behavior of ytterbium cations in a LiCl-KCl melt was investigated by electrochemical and UV-VIS absorption spectroscopy methods. In the LiCl-KCl melt, ytterbium exists with divalent and trivalent oxidation states. The electrochemical results showed that the electrochemical reactions of the Yb2+/3+ are reversible and controlled by their diffusion rates. UV-VIS absorption spectroscopy results indicate that the Yb2+ and Yb3+ ions in the LiCl-KCl melt have a few strong absorption bands below 400 nm. Additionally, the molar absorptivities of these electronic transitions of Yb2+ and Yb3+ in LiCl-KCl melt are reported.

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“…Absorption spectroscopy has been widely used to identify chemical species and in particular to monitor reactions in molten salts. 19,22,26,27 Figure 3 shows the electronic absorption spectra of LiCl-KCl eutectic melts containing UCl 3 , NdCl 3 , and CeCl 3 . Prior to Li 2 O addition, U 3+ and Ce 3+ exhibit their characteristic f-d transitions at 400-700 nm and 250-350 nm, respectively.…”

Section: Resultsmentioning

confidence: 99%

“…20,21 Electrochemical studies were performed using a quartz tube (20 mm in outer diameter and 2 mm in wall thickness), whereas the absorption spectroscopic studies used 350 mm long quartz tubes (outer diameter of 10 mm) finished with a quartz cuvette (path length 1 cm). 22 W wire (Alfa Aesar, diameter 0.2 mm) and glassy carbon (Alfa Aesar, diameter 3 mm) electrodes were used as the working and counter electrodes, respectively. The W wire electrode was mechanically polished with sand paper prior to use.…”

Section: Methodsmentioning

confidence: 99%

Electrochemical and Spectroscopic Monitoring of Interactions of Oxide Ion with U (III) and Ln (III) (Ln = Nd, Ce, and La) in LiCl-KCl Melts

Choi

Bae

Park

2017

J. Electrochem. Soc.

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Using cyclic voltammetry and UV-vis absorption spectroscopic methods, we studied the precipitation reactions of trivalent uranium and lanthanides (Nd, Ce, and La) with the oxide ion in LiCl-KCl molten salts, which are likely side reactions during the electrorefining process for nuclear fuel treatment. The in situ electrochemical and spectroscopic monitoring demonstrated that U 3+ consumed O 2− with the mole ratio of 2:1, whereas the lanthanide ions reacted with O 2− with the mole ratio of 1:1. Raman spectroscopy and X-ray diffraction were also employed to analyze the precipitates, confirming that U 3+ was precipitated and oxidized into UO 2 , while the trivalent lanthanide ions formed oxychlorides (LnOCl). As a preliminary study of actinide co-precipitation, we also electrochemically monitored the precipitation reactions in a mixed melt containing uranium and lanthanides, demonstrating a higher reactivity of the former with the oxide ion in LiCl-KCl. Understanding the chemical reactions in chloride-based molten salts at high temperatures is of fundamental importance for developing pyroprocessing technologies, which have been extensively examined over the last 30 years as a promising solution for accumulated spent nuclear fuel. [1][2][3][4] In particular, the electrochemical behaviors of actinides and lanthanides in LiCl-KCl melts have been widely studied to explain the fundamental electrochemical reactions in the electrorefining process, which partitions reusable metals and highly radioactive fission products.5-7 However, before the commercialization of this technology, it is necessary to obtain comprehensive insight of the molten salt chemistry of trace elements dissolved from the spent nuclear fuel, and the additives and/or impurities that enter during the process. 8,9 Li 2 O is a critical ingredient for the electrochemical reduction of spent oxide fuel. It affords O 2− ions that should diffuse to the anode at the beginning of the reduction process, and controls the O 2− concentration in the LiCl melt to prevent the Pt cathode from dissolving. 3 However, a trace amount of Li 2 O likely remains in the reduced fuel, even after distilling out the molten salt at the end of the oxide reduction process, and can enter the next process. During the electrorefining process, the oxide ion may react with trivalent actinide and lanthanide ions in the LiCl-KCl eutectic melt, affording insoluble oxides and oxychlorides 10,11 which contaminate the salt and reduce the purity and yields of recovered uranium. In addition, unreduced lanthanide oxides in the metal fuel feed play the role of oxo-donor in the LiClKCl melt.12 Therefore, knowledge of the reactions between the actinide/lanthanide ions and the oxide ion in the molten salt could lead to improvement in the electrorefining technology. Several research groups have studied such reactions by potentiometric titration of the oxide ion in the melt and product characterization, in order to estimate the thermodynamic properties for oxide reduction 10,12-15 and to partition lanthan...

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Electrochemical preparation and spectroelectrochemical study of neptunium chloride complexes in LiCl–KCl eutectic melts

Cited by 11 publications

References 28 publications

Electrochemical Formation of Divalent Samarium Cation and Its Characteristics in LiCl–KCl Melt

Electrochemical Formation of Divalent Samarium Cation and Its Characteristics in LiCl–KCl Melt

Investigation of the Electrochemical Behavior of Ytterbium Cations in LiCl-KCl Melt Using Spectro-Electrochemical Methods

Electrochemical and Spectroscopic Monitoring of Interactions of Oxide Ion with U (III) and Ln (III) (Ln = Nd, Ce, and La) in LiCl-KCl Melts

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