Electrode processes in the KF–AlF3–Al2O3 melt

Padamata, Sai Krishna; Yasinskiy, Andrey; Polyakov, P. V.

doi:10.1039/d0nj00016g

Cited by 21 publications

(15 citation statements)

References 36 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Padamata et al performed electrolysis in VEC using Cu 90 Al 10 anode and tungsten cathode in alumina-saturated KF-AlF 3 melt (with CR 1.4) at 800 °C. 26 The cell voltage was stable for the first 4 h, however, the voltage increased from 4.2 to 5.8 V in the next 14 h. The increase in the cell voltage could be due to an increase in oxide scale thickness during the electrolysis (oxide scale thickness ≈ 140 μm) or the presence of CuF 2 scale between the anode and the oxide scale. The current efficiency of the process was 84.1%, and the aluminium purity was 99.4%, where the main impurities were Si (0.157 wt%), Fe (0.253 wt%) and Cu (0.0984 wt%).…”

Section: Inert Anode Materialsmentioning

confidence: 91%

Review—Primary Production of Aluminium with Oxygen Evolving Anodes

Padamata

Singh

Haarberg

et al. 2023

J. Electrochem. Soc.

Self Cite

View full text Add to dashboard Cite

Due to environmental and economic concerns, carbon-free aluminium production has been an ultimate goal for aluminium industries. For the past few decades, a considerable amount of research has been conducted to find an inert anode material that could replace the consumable carbon anodes for aluminium electrolysis. Anodic materials such as metals, ceramics, and cermets have been studied extensively. All these anode materials have their advantages and disadvantages. However, metal alloys have proven effective because of their resistance to high-temperature corrosion and their ability to produce a protective oxide layer. For a successful adaptation of metallic anodes into the aluminium electrolysis cell, an electrolyte with a low operating temperature and high alumina solubility with good electrical conductivity is required. A wettable cathode with a shorter anode-to-cathode distance is preferred to compete with the Hall-Héroult process in terms of energy requirements. This review discusses the research progress on inert anodes, wettable cathodes, and electrolytes.

show abstract

Section: Inert Anode Materialsmentioning

confidence: 91%

Review—Primary Production of Aluminium with Oxygen Evolving Anodes

Padamata

Singh

Haarberg

et al. 2023

J. Electrochem. Soc.

Self Cite

View full text Add to dashboard Cite

show abstract

“…Moreover, the temperature of the process can be lowered to 700-850 °C by replacing sodium cryolite with low-temperature fluoride or chloride melts with considerable solubility of Al2O3. The promising option, the molten 1.3KF-AlF3 system has been studied elsewhere [89][90][91]. This process is patented [92] and now is under the laboratory scale studies [93] While Pt is successfully concentrated in the alloy, Re requires additional effort to be extracted as it is oxidized in a wide range of temperatures.…”

Section: One-step Methodsmentioning

confidence: 99%

Recovery of Noble Metals from Spent Catalysts: A Review

Padamata

Yasinskiy

Polyakov

et al. 2020

Metall Mater Trans B

Self Cite

View full text Add to dashboard Cite

During several past decades, plenty of technologies for platinum group metals (PGM) and rhenium (Re) recovery from electronic wastes and spent catalysts have been developed and published. The reasons for the rising interest in this area are: □ The abundance of these elements in the earth's crust is less than 10 -3 ppm (~6.6 10 4 t all over the world); □ global demand for PGMs is over 590 t; □ electronics and catalysts industry consumes over 90% of precious metals (about 65% of Pd, 45% of Pt and 84% of Rh are consumed in catalytic converters); □ properties of PGMs and Re (resistance towards corrosion and oxidation, high melting temperatures, electrical conductivity, and catalytic activity) are of great commercial interest.Even though several comprehensive reviews on the recovery of precious metals from spent catalysts have been recently published, several developments were out of the attention of the scientific community. The reviews divide the technologies into hydro-and pyrometallurgical ones. However, the variety of different approaches requires a more detailed classification. This article is an overview of the recently reported works and the comparison of different technologies in terms of extraction efficiency, environmental friendliness, and capital and operational expenditures. The new electrochemical method, which is now under development, is also presented.

show abstract

“…It is also stressed that metal fluoride is formed between the oxide layer and the metal during longer duration electrolysis at high current densities due to the oxide ion depletion in the infiltrated electrolyte. This phenomenon was studied in [15] and it was found that metal ions are reduced from this metal fluoride layer on the inner side of the oxide layer. An SEM image showing the presence of metallic copper on the inner side of the oxide layer removed from the 90Cu10Al anode after long term polarization is shown in Fig.…”

Section: Mechanisms Of Anode Corrosion and Aluminium Contaminationmentioning

confidence: 99%

“…The same can occur at different quasi-inert anodes at proper potentials. However, significant diffusion limitations were observed in [15] where limiting current densities were as low as 0.3-0.8 A/cm 2 in KF -AlF3 melts at 750-850 °C.…”

Section: Mechanisms Of Anode Corrosion and Aluminium Contaminationmentioning

confidence: 99%

“…The 90Cu-10Al anode, the aluminium oxide suspension based on the KF-AlF3-Al2O3 system with a volume fraction no more than 0.09 (with 5% Al2O3) at a temperature of at least 750 °C are recommended for further studies. The electrolysis test was performed by using 90Cu-10Al anode and tungsten cathode at 800 °C in KF-AlF3-Al2O3 (cryolite ratio = 1.4) for 18 hours [15]. The current efficiency of 84.4% was attained with a produced aluminium purity of 99.4%.…”

Section: Cu -Al Alloymentioning

confidence: 99%

See 1 more Smart Citation

An update on inert anodes for aluminium electrolysis

Yasinskiy¹,

Padamata²,

Polyakov³

et al. 2020

nfm

View full text Add to dashboard Cite

This update includes the literature related to the inert anodes which were published in the past decade. The metallic anodes are widely regarded as promising candidates to replace the carbon anodes due to its attractive properties like good electrical conductivity, easy to manufacture and high resistance to high thermal shocks. The metals have been tested in pure state and alloy (binary, ternary) form. The oxide scale formed on the anode surface acts as a barrier between the electrolyte and the anode which protects the anode from being dissolved. The layer of molten fluorides is formed between the scale and the metal anode after a certain time of polarization and the oxide scale acts as a bipolar electrode. Metal like Cu is reduced at the internal side of the scale. This paper elaborates the effects of various parameters on the performance of the anode. Cu-based alloys (Cu -Ni-Fe and Cu-Al) have shown promising results and could perform well in low-temperature electrolytes. It has been well established that the Cu content in Cu-Ni-Fe and Cu-Al alloys plays a major role in the metal dissolution as the CuO/Cu2O scales formed on the outer layer act as a sacrificial one. The corrosion rate of an anode can be reduced by decreasing the operating temperature which is possible by using the KF-AlF3 melts. The use of suspensions can increase the purity of the produced metal by stopping the anode products to come in contact with cathode metal.Many industries including RUSAL and ELYSIS are still conducting a considerable amount of research to develop an inert anode and are expecting to have a carbon-free cell in the nearest future.

show abstract

Electrode processes in the KF–AlF₃–Al₂O₃ melt

Abstract: SEM-EDX image of the oxide layer on the surface of the 90Cu–Al anode after the electrolysis process.

Cited by 21 publications

References 36 publications

Review—Primary Production of Aluminium with Oxygen Evolving Anodes

Review—Primary Production of Aluminium with Oxygen Evolving Anodes

Recovery of Noble Metals from Spent Catalysts: A Review

An update on inert anodes for aluminium electrolysis

Contact Info

Product

Resources

About