Anodic Dissolution Behavior of Al Alloys Containing Al₆Fe or β-AlFeSi in EmImCl–AlCl₃ Electrolyte During Electrorefining

Abstract

To produce over 99.9% of high-purity Al from Al alloys containing Al6Fe or β-AlFeSi through electrorefining, their anodic dissolution and cathodic electrodeposition characteristics should be clarified. In this study, the anodic dissolution and cathodic electrodeposition behavior of Al–Fe binary and Al–Fe–Si ternary alloys were investigated in an EmImCl–AlCl3 ionic liquid electrolyte at 323 K. Anodic polarization measurements, constant potential electrolysis, X-ray diffraction (XRD), scanning electron microscopy (SEM), field-emission SEM (FE-SEM), and energy dispersive spectroscopy (EDS) were used to study the anode and electrodeposits on the cathode. Constant potential electrolysis showed that Fe dissolved from Al6Fe in the Al–Fe anode at 0.7 V vs Al/Al(III) and from β-AlFeSi in the Al–Fe–Si anode at 1.4 V and was co-deposited with Al on the cathode. Notably, Si did not dissolve from β-AlFeSi at either potential. A combination of controlled anodic dissolution potential and the use of the Al alloy containing β-AlFeSi further suppressed the dissolution and cathodic co-deposition of Fe, affording high-purity Al on the cathode. This suggests that Al alloys with intermetallic compounds that are less likely to dissolve Fe at the anode are optimal for obtaining over 99.9% of high-purity Al from Al alloys containing Fe in the electrorefining method.

Anodic Dissolution during Electrorefining of Al–Zn Alloys in Lewis Acidic AlCl₃–EmImCl Ionic Liquid

“…The authors proposed a recycling process using electrorefining as one solution to this problem. [17][18][19][20] In electrorefining with scrap Al, understanding the anodic dissolution behavior of additive alloy elements is essential. However, in previous studies on electrorefining methods using molten salts [21][22][23] or ionic liquids, [24][25][26][27] these anodic dissolution behaviors were not clarified.…”

“…However, in previous studies on electrorefining methods using molten salts [21][22][23] or ionic liquids, [24][25][26][27] these anodic dissolution behaviors were not clarified. The authors clarified the processes involved in the anodic dissolution and electrorefining of Al-Si, 17 Al-Cu, 18 Al-Mn, 19 Al-Fe, and Al-Fe-Si alloys 20 as anodes using electrolytes at temperatures ranging from 323 to 423 K. Particularly, AlCl 3 -1-ethyl-3-methyl imidazolium chloride (EmImCl), obtained by mixing AlCl 3 and EmImCl, is capable of Al electrodeposition at room temperature. Therefore, the authors focused on it as an electrolyte for targeted energy-saving electrorefining.…”