Conditions and Mechanisms of Gas Emissions from Didymium Electrolysis and Its Process Control

Milicevic, Ksenija; Feldhaus, Dominic; Friedrich, Bernd

doi:10.1007/978-3-319-72284-9_187

Cited by 8 publications

(21 citation statements)

References 13 publications

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“…Carbon monoxide was observed in variable quantities, but always below 600 ppm. After a certain period of deposition time, the quantity of CO became substantially smaller, which might be attributed to the partial passivation of the anode active sites with oxygen containing ions [22]. CF 4 was recorded in very small quantities, well below 10 ppm.…”

Section: Resultsmentioning

confidence: 97%

“…When a GC electrode is used, the produced oxygen species can subsequently react with carbon producing CO and CO 2 . With F − present, CF 4 and C 2 F 6 gases could also be evolved from a GC anode [22,35]. Serious efforts by the workers in this field are devoted to restricting the gas evolution to only oxygen, if possible.…”

Section: Resultsmentioning

confidence: 99%

“…The electrolyte consisted of 87.5 wt.% neodymium fluoride (NdF 3 , Treibacher, Althofen, Austria, ≥99.9%) and 12.5 wt.% lithium fluoride (LiF, STREM Chemicals, Inc., Newburyport, MA, United States, 99.9%). This molar ratio of 47.5 mol% NdF 3 and 52.5 mol% LiF proved to be the most suitable in terms of the melting temperature and viscosity of the electrolyte [22]. The preparation of these electrolyte components included drying for 24 h at 523 K before the two powders were premixed, fed into a high purity graphite crucible, then melted and homogenized in a vacuum induction furnace under an argon atmosphere of 1800 mbar at up to 1373 K. An additional chemical compound was added to the electrolyte, neodymium oxide (Nd 2 O 3 , Treibacher, Althofen, Austria, 99.8%), which was dried for 24 h at 393 K. In order to make this material more suitable for the feeding process (the addition into the electrolyte already in the cell), the dried powder was pressed, crushed, and sieved to achieve a powder particle size between 0.71 mm and 2 mm.…”

Section: Methodsmentioning

confidence: 96%

“…Fluoride electrolytes are considered more suitable because of their higher conductivity, lower hygroscopy, and higher current efficiency of the neodymium deposition compared to the chloride melts [17,18]. Most of the molten fluoride electrolytes for Nd electrowinning was found in the literature reference LiF (NaF or KF) with CaF 2 (or BaF 3 ) [8,10,[17][18][19][20][21][22][23][24][25][26][27][28][29]. NdF 3 and Nd 2 O 3 serve as sources of neodymium in such fluoride melts.…”

Section: Introductionmentioning

confidence: 99%

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Investigation on the Electrochemical Behaviour and Deposition Mechanism of Neodymium in NdF3–LiF–Nd2O3 Melt on Mo Electrode

Cvetković

Feldhaus

Vukićević

et al. 2020

Metals

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Neodymium was electrochemically deposited from NdF3–LiF–Nd2O3 molten salt electrolyte onto the Mo electrode at temperatures close to 1273 K. Cyclic voltammetry and chronoamperometry measurements were the applied electrochemical methods. Metallic neodymium is obtained by potentiostatic deposition. The optical microscopy and XRD were used to analyze the electrolyte, the working electrode surface, and the deposit on the electrode. It was established that Nd(III) ions were reduced to Nd metals in two steps: Nd(III) + e− → Nd(II) at potential ≈−0.55 V vs. W and Nd(II) + 2e− → Nd(0) at ≈−0.83 V vs. W. Both of these processes are reversible and under mass transfer control. Upon deposition under the regime of relatively small deposition overpotential of −0.10 V to −0.20 V, and after the electrolyte was cooled off, Nd metal was observed at the surface of the Mo electrode. CO and CF4 were gases registered as being evolved at the anode. CO and CF4 evolution were observed in quantities below 600 ppm and 10 ppm, respectively.

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Section: Resultsmentioning

confidence: 97%

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Investigation on the Electrochemical Behaviour and Deposition Mechanism of Neodymium in NdF3–LiF–Nd2O3 Melt on Mo Electrode

Cvetković

Feldhaus

Vukićević

et al. 2020

Metals

Self Cite

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“…The current high demand for neodymium (Nd) and praseodymium (Pr) and their alloys is attributed to their superior magnetic flux density needed for developing very strong permanent magnets [1,2]. These rare earth (RE) metals are mostly extracted from their oxides via molten salt electrolysis.…”

Section: Introductionmentioning

confidence: 99%

Dissolution and Online Monitoring of Nd and Pr Oxides in NdF3–PrF3–LiF Electrolytes

Senanu

Ratvik

Gudbrandsen

et al. 2021

Metals

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Concentrations of dissolved rare earth metal oxides, Nd2O3, and Pr2O3 or their mixtures in different fluoride electrolytes composed of NdF3, PrF3, and LiF at ca. 1040 °C were monitored using a graphite probe inserted into the electrolyte during the dissolution process. Fast voltage sweeps of 100 V/s were applied to the graphite probe, and the current response was measured. As the oxide concentration in the diffusion layer towards the electrode depletes, a passive layer is, at a certain point, formed on the probe, resulting in a current drop. The magnitude of the peak current attained before the formation of the passive layer reflects the concentration of the dissolved oxide and, thus, is applied to determine the oxide concentration. The oxide concentration in the electrolyte samples determined using the inert gas fusion technique showed a good correlation to the peak current determined by the probe.

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From lunar regolith to oxygen and structural materials: an integrated conceptual design

et al. 2022

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To enable a long-term presence of humans in space, it is essential to use extraterrestrial raw materials to reduce the need for transporting resources or produced materials from Earth. In recent years, a lot of research has been conducted on different ISRU processes, such as regolith excavation, mineral processing and the extraction of oxygen using metallurgical processes. However, it is not sufficient to just focus on a single process but also to focus on how the different processes interact. Therefore, RWTH Aachen’s Integrated Conceptual Design presents a novel concept for the production of oxygen and high-quality metal materials. To meet the challenges of mining in space, selective mining is used to provide the best possible blend based on the original material of the deposit. This process is followed by mineral processing to provide a high-quality ilmenite-rich concentrate, the input material for metallurgical processes. Using the novel MOSARI technique, consisting of molten salt electrolysis and metallothermic reduction, oxygen and metal materials can be recovered. Furthermore, this represents a zero-waste approach for the complete utilization of the material.

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Conditions and Mechanisms of Gas Emissions from Didymium Electrolysis and Its Process Control

Cited by 8 publications

References 13 publications

Investigation on the Electrochemical Behaviour and Deposition Mechanism of Neodymium in NdF3–LiF–Nd2O3 Melt on Mo Electrode

Investigation on the Electrochemical Behaviour and Deposition Mechanism of Neodymium in NdF3–LiF–Nd2O3 Melt on Mo Electrode

Dissolution and Online Monitoring of Nd and Pr Oxides in NdF3–PrF3–LiF Electrolytes

From lunar regolith to oxygen and structural materials: an integrated conceptual design

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