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

The anodic dissolution reaction of Al–Zn alloys containing a Zn solid solution in Lewis acidic AlCl₃–1-ethyl-3-methyl-imidazolium chloride (EmImCl) ionic liquids at various potentials is investigated herein. An enrichment layer was formed on the anode surface after applying constant potentials of 0.3 and 0.7 V in the 60 mol%AlCl₃–40 %EmImCl (60 % AlCl₃) electrolyte and 0.2 V in the 67 mol%AlCl₃–33 %EmImCl (67 %AlCl₃) electrolyte. Consequently, metallic Zn was detected in the enriched layer using X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). Notably, in the 60 %AlCl₃ electrolyte, high-purity Al was obtained at a much nobler potential than the dissolution potential of pure Zn, suggesting that the anodic dissolution of Zn from the Al–Zn alloy into the electrolyte was difficult. When electrorefining Al–Zn alloy anodes containing a Zn solid solution using 60 %AlCl₃, which has lower acidity than the 67 %AlCl₃ electrolyte, it is possible to increase the anodic potential from 0.2 to 0.7 V. At this higher potential, high-purity Al is obtained at the cathode.