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

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.