Electrochemically produced divalent neodymium in chloride melt

Yamana, Hideaki; Park, Byung Gi; Shirai, Osamu; Fujii, Toshiyuki; Uehara, Akihiro; Moriyama, Hirotake

doi:10.1016/j.jallcom.2005.04.104

Cited by 50 publications

(43 citation statements)

References 9 publications

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“…39 The peak potential in region B, on the other hand, shifts slightly depending on the scan rate as also observed by others. 22,26 From Fig. 2, the maximal (peak) cathodic current densities were extracted for regions A and B as a function of the scan rate.…”

Section: Cyclic Voltammetry Studies Of Redox Transitions During Nd Elmentioning

confidence: 99%

Electrodeposition of Neodymium from NdCl₃-Containing Eutectic LiCl–KCl Melts Investigated Using Voltammetry and Diffusion-Reaction Modeling

Shen

Akolkar

2017

J. Electrochem. Soc.

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Electrodeposition of neodymium (Nd) metal from NdCl 3 -containing molten LiCl-KCl eutectic melts was investigated using voltammetry and diffusion-reaction modeling. Voltammetry studies confirmed that Nd electrodeposition is a two-step reduction process involving first a reversible one-electron transfer reduction of Nd 3+ to Nd 2+ , followed by quasi-reversible reduction of Nd 2+ to Nd metal. In the electrode potential range where Nd 3+ is reduced to Nd 2+ , the peak current density measured in a voltammetry scan showed good agreement with the classical Randles-Sevcik model for reversible soluble-soluble redox transitions. However, in the potential range where Nd 2+ is reduced to Nd metal, the experimentally measured peak currents in the voltammogram were substantially lower than those predicted by applying the Berzins-Delahay model for reversible soluble-insoluble redox transitions. In the present work, this discrepancy was addressed using transient diffusion-reaction modeling, which accounted for the multivalent (Nd 2+ and Nd 3+ ) species transport and their multi-step reduction to Nd metal. The diffusion-reaction model accurately predicts the voltammetric response during Nd electrodeposition in a broad range of operating conditions (species concentrations and voltammetry scan rates), while providing access to the kinetic parameters governing Nd electrodeposition from halide melts. The approach presented herein may also be applied to other electrodeposition systems which undergo multivalent redox transitions at the electrode-electrolyte interface. Rare earth elements enable important functions in numerous applications. They are used in permanent magnets in electric motors and electronic memory storage, in catalysts for automobile catalytic converters and for petroleum refining, and in phosphors for energyefficient lighting and color displays. 1 Due to their rare occurrence in nature and the complexity associated with extracting and refining them, rare earth metals are very expensive and face potential supply risks. For future sustainable use of rare earth metals, the recovery and recycling of these materials from product waste is of great practical importance. 2 For energy-efficient recovery of rare earth elements, one promising technique is the electrolytic refining of these metals from waste streams such as electronic waste. 3 Electrochemical processing, i.e., electrowinning or electrorefining, using high temperature molten salt electrolytes is particularly attractive, because molten salts offer high ionic conductivity, 4 good electrochemical stability, 5,6 and low interfacial charge transfer resistance. 7,8 These are desirable attributes for industrial scale process implementation. Furthermore, high-temperature molten salt electrochemical systems offer industrially relevant rates of processing (high current densities) and ease of scalability to large-volume manufacturing at low cost. 9,10 Consequently, the characterization of the electrochemical behavior of rare earth metals in molten salts is important, bec...

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Section: Cyclic Voltammetry Studies Of Redox Transitions During Nd Elmentioning

confidence: 99%

Electrodeposition of Neodymium from NdCl₃-Containing Eutectic LiCl–KCl Melts Investigated Using Voltammetry and Diffusion-Reaction Modeling

Shen

Akolkar

2017

J. Electrochem. Soc.

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“…According to professor Zhu s research 1) , the lower current efciency for Nd extraction from NdCl 3 -KCl melts is partly caused by Nd consumption and corresponding to Nd(II) formation by the comproportionation reaction between the Nd(0) and Nd(III). A. Novoselova et al 2) , S.Vandarkuzhali et al 3) and Hajimu Yamana et al 4) have con rmed that the Nd(III) ions in the NdCl 3 -KCl melts are reduced to Nd(0) through two consecutive steps, i.e., Nd(III)→Nd(II) and Nd(II)→Nd(0). Therefore, they have concluded that the Nd(II) ions can stably exist in molten LiCl-KCl-NdCl 3 at 773 K 4) and LiCl-KCl-CsCl-NdCl 3 melts after electrolysis at 810-840 K 2) .…”

Section: Introductionmentioning

confidence: 98%

The Effects of NdF2 on Current Efficiency of Nd Extraction from NdF3-LiF-Nd2O3 Melts

Liu

Huang

2017

Mater. Trans.

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In this paper, the cyclic voltammetry was applied to investigate the electrochemical reduction processes of Nd(III) ions in NdF 3 -LiF melts with or without excessive metal Nd. Equilibrium experiments were carried out in NdF 3 -LiF melts with excessive spheric metal Nd to investigate the relationship between the NdF 3 :LiF mass ratio and NdF 2 concentration. Electrolysis experiments were performed in NdF 3 -LiF-Nd 2 O 3 melts with different NdF 3 :LiF mass ratios to explore the relationship between the NdF 2 concentration and the current ef ciency.The results indicated that Nd(III) ions in the melts were reduced in two steps, i.e., Nd(III)→Nd(II) and Nd(II)→Nd(0). NdF 2 could be formed by the comproportionation reaction between Nd(III) and Nd(0) and could stably exist in NdF 3 -LiF melts containing metal Nd(0). NdF 2 mass concentration in the melts decreased from 45.5% to 36.4% with the increase of NdF 3 -LiF mass ratio from 7:3 to 9:1 in NdF 3 -LiF melts containing excessive spheric metal Nd, which resulted in a higher current ef ciency during the electrolysis. And the highest current ef ciency of about 50% for Nd extraction has been obtained by electrolysis in NdF 3 -LiF (9:1 mass ratio) melts with Nd 2 O 3 (2%, mass concentration) at

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“…However, the reports for the electrochemical behavior of Nd in molten chlorides have been limited for LiCl-KCl [8][9][10], NaCl-CaCl 2 [9] and LiCl-CaCl 2 [10] eutectic melts. In order to assess the refining performance of Nd, systematic data for the chemical stability of Nd(III) complex in various alkali chlorides is necessary.…”

Section: Introductionmentioning

confidence: 99%

Electrochemical and spectrophotometric study on neodymium ions in molten alkali chloride mixtures

Fukasawa

Uehara

Nagai

et al. 2011

Journal of Alloys and Compounds

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Electrochemically produced divalent neodymium in chloride melt

Cited by 50 publications

References 9 publications

Electrodeposition of Neodymium from NdCl₃-Containing Eutectic LiCl–KCl Melts Investigated Using Voltammetry and Diffusion-Reaction Modeling

Electrodeposition of Neodymium from NdCl₃-Containing Eutectic LiCl–KCl Melts Investigated Using Voltammetry and Diffusion-Reaction Modeling

The Effects of NdF<sub>2</sub> on Current Efficiency of Nd Extraction from NdF<sub>3</sub>-LiF-Nd<sub>2</sub>O<sub>3</sub> Melts

Electrochemical and spectrophotometric study on neodymium ions in molten alkali chloride mixtures

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Electrochemically produced divalent neodymium in chloride melt

Cited by 50 publications

References 9 publications

Electrodeposition of Neodymium from NdCl3-Containing Eutectic LiCl–KCl Melts Investigated Using Voltammetry and Diffusion-Reaction Modeling

Electrodeposition of Neodymium from NdCl3-Containing Eutectic LiCl–KCl Melts Investigated Using Voltammetry and Diffusion-Reaction Modeling

The Effects of NdF<sub>2</sub> on Current Efficiency of Nd Extraction from NdF<sub>3</sub>-LiF-Nd<sub>2</sub>O<sub>3</sub> Melts

Electrochemical and spectrophotometric study on neodymium ions in molten alkali chloride mixtures

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Electrodeposition of Neodymium from NdCl₃-Containing Eutectic LiCl–KCl Melts Investigated Using Voltammetry and Diffusion-Reaction Modeling

Electrodeposition of Neodymium from NdCl₃-Containing Eutectic LiCl–KCl Melts Investigated Using Voltammetry and Diffusion-Reaction Modeling