Redox potentials and electronic absorption spectra of dilute solutions of nickel and chromium chlorides in molten alkali chlorides

Smirnov, M.V.; Potapov, Alexei

doi:10.1016/0013-4686(94)85021-6

Cited by 29 publications

(42 citation statements)

References 11 publications

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“…The in situ analysis of electrolytically generated species in pyrochemical processes has previously been limited to EAS detection. 14,15 Nagai et al have investigated the {UO 2 } 2+ /{UO 2 } + redox equilibrium in a molten CsCl-NaCl eutectic using EAS spectroelectrochemistry. 14 Previously, XAS spectroelectrochemical investigations of actinides in room temperature solutions had been performed in thin-layer or poly(tetrafluoroethylene) electrochemical cells.…”

Section: Introductionmentioning

confidence: 99%

“…Of more industrial relevance would be an increased understanding of speciation with respect to electrochemical processes. The in situ analysis of electrolytically generated species in pyrochemical processes has previously been limited to EAS detection. , Nagai et al have investigated the {UO 2 } 2+ /{UO 2 } + redox equilibrium in a molten CsCl−NaCl eutectic using EAS spectroelectrochemistry . Previously, XAS spectroelectrochemical investigations of actinides in room temperature solutions had been performed in thin-layer or poly(tetrafluoroethylene) electrochemical cells. , However, these techniques are not readily applicable to high-temperature investigations.…”

Section: Introductionmentioning

confidence: 99%

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In Situ Spectroscopy and Spectroelectrochemistry of Uranium in High-Temperature Alkali Chloride Molten Salts

et al. 2008

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Soluble uranium chloride species, in the oxidation states of III+, IV+, V+, and VI+, have been chemically generated in high-temperature alkali chloride melts. These reactions were monitored by in situ electronic absorption spectroscopy. In situ X-ray absorption spectroscopy of uranium(VI) in a molten LiCl-KCl eutectic was used to determine the immediate coordination environment about the uranium. The dominant species in the melt was [UO 2Cl 4] (2-). Further analysis of the extended X-ray absorption fine structure data and Raman spectroscopy of the melts quenched back to room temperature indicated the possibility of ordering beyond the first coordination sphere of [UO 2Cl 4] (2-). The electrolytic generation of uranium(III) in a molten LiCl-KCl eutectic was also investigated. Anodic dissolution of uranium metal was found to be more efficient at producing uranium(III) in high-temperature melts than the cathodic reduction of uranium(IV). These high-temperature electrolytic processes were studied by in situ electronic absorption spectroelectrochemistry, and we have also developed in situ X-ray absorption spectroelectrochemistry techniques to probe both the uranium oxidation state and the uranium coordination environment in these melts.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

In Situ Spectroscopy and Spectroelectrochemistry of Uranium in High-Temperature Alkali Chloride Molten Salts

et al. 2008

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“…The temperature dependency of the NaCl-2CsCl system is larger than those in other molten chlorides, such as LiCl-KCl, NaCl, KCl, CsCl, NaCl-KCl, NaCl-CsCl and KCl-CsCl, [7,9]. This tendency of NaCl-2CsCl melts is common for U 4þ jU 3þ and Eu 3þ jEu 2þ couples in chloride melts [14,15].…”

Section: Ementioning

confidence: 92%

“…Electrochemically determined redox potentials of the Cr 3þ jCr 2þ couple in LiCl-KCl [3][4][5], NaCl-KCl [6,7] and CaCl 2 -NaCl melts [7,8] were reported. Smirnov et al [9] determined the formal redox potential of the Cr 3þ jCr 2þ couple, E 0 Cr 3þ jCr 2þ , by the spectroelectrochemical method in various alkaline metal chlorides. They found that the E 0 Cr 3þ jCr 2þ shifts negatively depending on the radius of the alkaline metal ions, and this was also found for the Ni 3þ jNi 2þ couple.…”

Section: Introductionmentioning

confidence: 99%

Electrochemical redox reactions of chromium and iron ions in molten NaCl–2CsCl eutectic for pyro-reprocessing of nuclear fuels

et al. 2008

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Basic electrochemical and spectroscopic properties of Cr 3? , Cr 2? , Fe 3? , and Fe 2? were studied to analyze the cyclic redox reactions of Cr and Fe, which may decrease the current efficiency of the electro-winning method using NaCl-2CsCl melts. The formal redox potentials of the Cr 3þ jCr 2þ and Fe 3þ jFe 2þ couples, E 0 Cr 3þ jCr 2þ and E 0 Fe 3þ jFe 2þ , in NaCl-2CsCl melts at 923 K were spectroelectrochemically determined to be -0.648 ± 0.005 V and À0:140AE 0:010 V vs: Cl 2 jCl À , respectively. These values were determined by measuring electromotive force and UV-VIS absorption spectra at varying concentration ratios of trivalent and divalent ions. Cyclic voltammetry was also carried out to examine the characteristics of the voltammograms for the Cr 3þ jCr 2þ and Fe 3þ jFe 2þ couples in NaCl-2CsCl melts. The E 0 Cr 3þ jCr 2þ determined by the spectroelectrochemical method was close to that determined by cyclic voltammetry ðÀ0:651 AE 0:006 V vs: Cl 2 jCl À Þ. The effect of temperature on the E 0 Cr 3þ jCr 2þ in NaCl-2CsCl melts was studied by cyclic voltammetry in the range from 823 to 1,023 K ðE 0 Cr 3þ jCr 2þ ¼ 0:00143T À 1:971 AE 0:005 V vs: Cl 2 jCl À Þ. Diffusion coefficients of Cr 3? and Cr 2? , D Cr 3þ and D Cr 2þ , were determined between 823 and 1,023 K to be D Cr 3þ ¼ 2:23 Â 10 À3 exp ðÀ4;135=TÞ and D Cr 2þ ¼ 3:34 Â 10 À3 expðÀ4;106=TÞ, respectively. Molar absorptivities of Cr 3? and Cr 2? in NaCl-2CsCl melts at 923 K were determined to be 77.8 ± 2.4 M -1 cm -1 at 17,670 cm -1 and 48.0 ± 1.4 M -1 cm -1 at 9,170 cm -1 , respectively. In addition, the effects of these ions on the cyclic redox reaction of the pyro-reprocessing process were discussed.

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“…Molten salt electrolysis as the preferred method for the preparation of refractory metals from anhydrous chromium chlorides (CrCl3 or CrCl2) has been extensively studied [1,[4][5][6][7][8][9]. However, chromium chlorides are unstable and have strong hydrolysis ability [1].…”

Section: Introductionmentioning

confidence: 99%

Direct electro-deposition of metallic chromium from K2CrO4 in the equimolar CaCl2-KCl molten salt and its reduction mechanism

Weng

Wang

Gong

et al. 2016

Electrochimica Acta

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Redox potentials and electronic absorption spectra of dilute solutions of nickel and chromium chlorides in molten alkali chlorides

Cited by 29 publications

References 11 publications

In Situ Spectroscopy and Spectroelectrochemistry of Uranium in High-Temperature Alkali Chloride Molten Salts

In Situ Spectroscopy and Spectroelectrochemistry of Uranium in High-Temperature Alkali Chloride Molten Salts

Electrochemical redox reactions of chromium and iron ions in molten NaCl–2CsCl eutectic for pyro-reprocessing of nuclear fuels

Direct electro-deposition of metallic chromium from K2CrO4 in the equimolar CaCl2-KCl molten salt and its reduction mechanism

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