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

To produce over 99.9% of high-purity Al from Al alloys containing Al6Fe or beta-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 beta-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 beta-AlFeSi at either potential. A combination of controlled anodic dissolution potential and the use of the Al alloy containing beta-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.