AluminumAluminum–scandiumScandium master alloysMaster alloy are highly demanded products used to create multi-functional aluminum alloysAluminum alloys and composites. A high cost of Al-Sc master alloysMaster alloy stops the automotiveAutomotive industry from using them widely. This research investigates the possibility to produce Al-ScAl-Sc master alloysMaster alloy via electrolysisElectrolysis of the LiF-AlF3-Sc2O3 melt. The kinetic parameters of the aluminumAluminum and scandiumScandium electrowinningElectrowinning were studied by means of voltammetryVoltammetry, stationary polarization, and electrolysisElectrolysis tests. The apparent limiting current density for co-deposition of AluminumAluminum and ScandiumScandium on tungsten cathodeCathode was in the range from 1.28 to 1.97 A.cm–2 in the temperature range from 860 to 940 °C. Based on the electrochemical measurements, the parameters for galvanostatic electrolysisElectrolysis were selected and electrolysisElectrolysis tests were carried out to obtain Al-Sc master alloysMaster alloy. The microstructureMicrostructure of the obtained Al-Sc master alloysMaster alloy was studied. It was possible to obtain Al-Sc alloysAl-Sc alloys with the concentration of Sc 0.68 wt.%.

strategic issue for rare metals manufacturers is availability of the own raw material base. Previously unused resources which include the lignites located at central watershed of the Yenisei river are becoming important due to depletion of traditional sources of raw materials. The comprehensive approach to the processing of the lignite which ensures the formation of sublimates germanium -enriched to 1,8 wt.% and ash rare earth metals-enriched to 1,2 wt.% was proposed. The regularities of rare earth metals leaching from ash residue with obtaining rich solutions suitable for further processing using selective sorbents have been studied.

New methods of liquid metals refining and separation operated with low energy consumption and environmental impact are highly desirable nowadays. This work presents an approach of Al refining and extraction from scrap in a thin layer of the multiple-pore molten salt electrochemical system, which appears promising. The new single-capillary cell design with a quasi-reference electrode on the TiB2 substrate was used to study the kinetics of aluminium reduction and dissolution in a narrow 1 mm-diameter channel filled with KF-AlF3 (1.1 < [KF]/[AlF3] < 1.5 mole/mole) or equimolar NaCl-KCl with N wt.% of AlF3 (3 < N < 20) at 700-850 degrees C. It was found that the chloride-based melts are more preferable than the fluoride mixtures due to the much bigger electrode potential window between Al and Alkali metal (1.3 vs. 0.4 V), higher apparent limiting currents (0.9 vs. 0.3 A cm(-2)) and lower overvoltage (4-16 vs. 66-247 mV at 0.1 A cm(-2)) resulted from the diffusion kinetics dominance. However, anodic dissolution of aluminium in NaCl-KCl-AlF3 may be chemical reaction-controlled with the exchange current density of 105 mA cm(-2), and the reaction order of 0.34 observed in the experiment. The temperature drastically affected the whole kinetics picture with the activation energy for alkali metal reduction found to be 94.762 kJ mole(-1). The preferable temperature for liquid metal refining was found to be 800 degrees C. The cathodic process in the KF-AlF3 melt has mixed kinetics. It possesses surprisingly low apparent diffusion limiting current (0.3 A cm(-2) at 800 degrees C and [KF]/[AlF3] = 1.1 mole/mole) and chemical reaction control at higher [KF]/[AlF3] (with exchange current density of 50 mA cm(-2) and the reaction order of 0.08 at [KF]/[AlF3] = 1.5 mole/mole). It may happen due to the co-deposition of Al and K with the evolution of solid cryolite. The composition of the melt plays a crucial role in refining performance. The optimal [KF]/[AlF3] for Al refining is 1.2 mole/mole. It allows operating at a current density not higher than 0.4 A cm(-2) with a thickness of a thin-layer system less than 60 mu m. The preferable AlF3 concentration in the NaCl-KCl-AlF3 composition is 10%. It allows operating at 1.4 A cm(-2) with a thickness of 22 mu m or lower. (c) 2020 Elsevier Ltd. All rights reserved.

This work is a contribution to the approach for Al purification and extraction from scrap using the thin-layer multiple-capillary molten salt electrochemical system. The single- and multiple-capillary cells were designed and used to study the kinetics of aluminium reduction in LiF–AlF3 and equimolar NaCl–KCl with 10 wt.% AlF3 addition at 720–850 °C. The cathodic process on the vertical liquid aluminium electrode in NaCl–KCl (+10 wt.% AlF3) in the 2.5 mm length capillary had mixed kinetics with signs of both diffusion and chemical reaction control. The apparent mass transport coefficient changed from 5.6∙10−3 cm.s−1 to 13.1∙10−3 cm.s−1 in the mentioned temperature range. The dependence between the mass transport coefficient and temperature follows an Arrhenius-type behaviour with an activation energy equal to 60.5 kJ.mol−1. In the multiple-capillary laboratory electrolysis cell, galvanostatic electrolysis in a 64LiF–36AlF3 melt showed that the electrochemical refinery can be performed at a current density of 1 A.cm−2 or higher with a total voltage drop of around 2.0 V and specific energy consumption of about 6–7 kWh.kg−1. The resistance fluctuated between 0.9 and 1.4 Ω during the electrolysis depending on the current density. Thin-layer aluminium recycling and refinery seems to be a promising approach capable of producing high-purity aluminium with low specific energy consumption.

The liquid metal refining industry has a demand for new technologies operated at low energy consumption and environmental impact nowadays. This work addresses an approach for Al purification and extraction from scrap in a thin layer of the multiple-capillary molten salt electrochemical system. The two types of single-capillary cells with quasi-reference electrodes were used to study the kinetics of aluminium reduction and dissolution in a narrow (Ø x length) 1 × 1 and 1 × 5 mm channel filled with liquid LiF-AlF3 or equimolar NaCl-KCl with the AlF3 addition at 850 °C. A multiple-capillary Al refinery process can be designed to significantly reduce the specific energy consumption. The new refinery process can be performed at high current densities. The single-capillary electrolysis can be used for kinetics studies. Thin-layer cells should be operated at a thickness no more than 5 mm to compensate the high resistance which may vary in the range from 0.7 to 2.5 Ω at this capillary length. The 64LiF-36AlF3 melt can be used as an electrolyte for the thin-layer electrolysis due to the high electrical conductivity, the wide potential window between Al and Li reduction, and the low liquidus temperature.