Electrochemical reduction and dissolution of liquid aluminium in thin layers of molten halides

Yasinskiy, Andrey; Polyakov, P. V.; Yang, Youjian; Wang, Zhaowen; Suzdaltsev, Andrey; Moiseenko, Ilya; Padamata, Sai Krishna

doi:10.1016/j.electacta.2020.137436

Cited by 8 publications

(6 citation statements)

References 36 publications

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“…61 The diffusion layer thickness could vary from tens to hundreds of micrometers in size for different systems. [61][62][63][64] Diffusion layer thickness (h) is reported to be approximately 250 μm in the molten Cl salt mixture of interest in this study. 65 The diffusion coefficient of transition ions in molten salts are approximately in the range of 1-4 × 10 −5 cm 2 s −1 in the molten salt of interest at similar temperature.…”

Section: Resultsmentioning

confidence: 99%

Electrochemical Corrosion Studies in Molten Chloride Salts

Ghaznavi

Persaud²,

Newman³

2022

J. Electrochem. Soc.

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This study investigates corrosion of Fe-(Cr)-Ni model alloys in eutectic molten chloride salt mixtures that broadly simulate the heat transfer circuits of molten salt cooled nuclear reactors. The primary focus is impurity-driven corrosion and selective dissolution of electrochemically reactive element(s) (dealloying), which are known degradation modes for Fe- and Ni-based alloys in molten salts. This study demonstrates that a Mg rod performs close to a true Mg|Mg2+ reference electrode system in a MgCl2 containing mixture. Mg dynamic reference electrodes validated the performance of the ordinary Mg reference electrode. The residual moisture content in molten salts is measured by cathodic polarization of Pt, which showed that convection of molten salts, after step-wise heating, through a bundle of Mg ribbons dropped the moisture content by 30-fold. The effect of impurities in the molten salt mixture, moisture and NiCl2, on dealloying was also investigated at low homologous temperature. It was found that the universal parting limit for dealloying is decreased to a value of approximately 32 at.% Fe when Ni from the parent alloy is close to equilibrium with Ni2+ ions added to the eutectic molten salts. Results support the percolation/surface diffusion concept for dealloying in molten salts at low homologous temperature.

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Section: Resultsmentioning

confidence: 99%

Electrochemical Corrosion Studies in Molten Chloride Salts

Ghaznavi

Persaud²,

Newman³

2022

J. Electrochem. Soc.

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“…[22][23][24] Similar dependences were found earlier in the KF-AlF 3 melts. 36,37,41 Electrolysis tests.-In Table II one can see the parameters and results of the electrolysis tests in the KF-AlF 3 -Al 2 O 3 and KF-NaF-AlF 3 -Al 2 O 3 melts saturated with alumina with the molar ratio equal to ([KF]+[NaF])/[AlF 3 ] = 1.3 and 1.5 mol mol −1 at 750 °C and 800 °C, respectively. The amperage was the same at all tests and was equal to 16-20 A.…”

Section: Resultsmentioning

confidence: 99%

“…The interest to these melts can also be explained by the fact that they are equally well suited for both aluminum and aluminum master alloys production, 35 as well as for the spent catalyst reprocessing. 36,37 In this work, the suggestions regarding the physicochemical processes that occur on electrodes and in the ACD during electrolysis of low-temperature KF-AlF 3 -based melts are considered. The existing data both on electrode processes and physicochemical properties of the melts under study are taken into account.…”

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confidence: 99%

Towards the Stability of Low-Temperature Aluminum Electrolysis

Suzdaltsev

Nikolaev

Zaikov

2021

J. Electrochem. Soc.

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The results of several different tests related to the low-temperature aluminum electrolysis were considered in this work. The role of mass transfer processes in the anode-cathode space was recommended to be significant during electrolysis in the low-temperature KF-AlF3 and NaF-AlF3-based melts. The stationary polarization and voltammetry methods were applied in order to study the kinetics of the electrode processes on the carbon and metal electrodes in the KF-AlF3-Al2O3 melts and to select the electrolysis parameters. The schemes of electrode processes were suggested on the basis of electrochemical tests, the flows of substances in the anode-cathode distance were analyzed and the main reasons of the cathode current efficiency decrease during the low-temperature electrolysis in the KF-AlF3-Al2O3 and KF-NaF-AlF3-Al2O3 melts were discussed. It was revealed that the cathode current density should not exceed 0.4–0.55 A cm−2 during the electrolysis at 750 °C–800 °C.

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“…in the temperature range of 750 to 850 • C at CR = 2.0 [34]. The LiF-AlF 3 melts also demonstrated good performance in the aluminum refinery studies [37,38]. The reduction kinetics of Al from the spent catalyst in molten salts has been poorly examined, and studying its electrochemical behavior in various molten salts can promote understanding of the recovery parameters for the PGM.…”

Section: Introductionmentioning

confidence: 99%

Towards Understanding the Cathode Process Mechanism and Kinetics in Molten LiF–AlF3 during the Treatment of Spent Pt/Al2O3 Catalysts

Yasinskiy

Padamata

Stopić

et al. 2021

Metals

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Electrochemical decomposition of spent catalyst dissolved in molten salts is a promising approach for the extraction of precious metals from them. This article reports the results of the study of aluminum electrowinning from the xLiF–(1-x)AlF3 melt (x = 0.64; 0.85) containing 0–5 wt.% of spent petroleum Pt/γ-Al2O3 catalyst on a tungsten electrode at 740–800 °C through cyclic voltammetry and chronoamperometry. The results evidence that the aluminum reduction in the LiF–AlF3 melts is a diffusion-controlled two-step process. Both one-electron and two-electron steps occur simultaneously at close (or same) potentials, which affect the cyclic voltammograms. The diffusion coefficients of electroactive species for the one-electron process were (2.20–6.50)∙10−6 cm2·s–1, and for the two-electron process, they were (0.15–2.20)−6 cm2·s−1. The numbers of electrons found from the chronoamperometry data were in the range from 1.06 to 1.90, indicating the variations of the partial current densities of the one- and two-electron processes. The 64LiF–36AlF3 melt with about 2.5 wt.% of the spent catalysts seems a better electrolyte for the catalyst treatment in terms of cathodic process and alumina solubility, and the range of temperatures from 780 to 800 °C is applicable. The mechanism of aluminum reduction from the studied melts seems complicated and deserves further study to find the optimal process parameters for aluminum reduction during the spent catalyst treatment and the primary metal production as well.

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Electrochemical reduction and dissolution of liquid aluminium in thin layers of molten halides

Cited by 8 publications

References 36 publications

Electrochemical Corrosion Studies in Molten Chloride Salts

Electrochemical Corrosion Studies in Molten Chloride Salts

Towards the Stability of Low-Temperature Aluminum Electrolysis

Towards Understanding the Cathode Process Mechanism and Kinetics in Molten LiF–AlF3 during the Treatment of Spent Pt/Al2O3 Catalysts

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