Clarification of the anodic dissolution behavior of metallurgical structures during electrorefining of Al-Mn alloys in a 1-ethyl-3-methyl-imidazolium chloride-AlCl3 ionic liquid

Abstract

Recycling Al is crucial to reduce the energy and environmental costs of Al manufacturing; however, the reclamation efficiency of high-quality Al from Al alloys is limited by the co-deposition of impurities during the electrorefining process. To address this issue, the anodic dissolution behavior of metallurgical structures within various Al-Mn binary alloys in 1-ethyl-3-methyl-imidazolium chloride-AlCl3 ionic liquid was investigated. During the constant-potential electrolysis of Al-1.5%Mn cast and cold-rolled plate alloys, an enriched layer derived from Mn solid solution was formed at an electrorefining potential of 0.2 V; this was attributed to preferential dissolution of Al in the matrix phase, followed by Mn accumulation at the Al surface. Furthermore, dissolution of the Al-Mn-Fe and Al-Mn intermetallic compounds occurred at 0.6 and 1.0 V, respectively; thus, the dissolution behavior of Mn in the Al-Mn alloys differed between the Mn solid solution in the matrix phase and the Mn-containing intermetallic compounds. These results indicate that by controlling the microstructure of the Al-Mn alloy and the applied anodic potential, the dissolution of Mn into the 1-ethyl-3-methyl-imidazolium chloride-AlCl3 electrolyte can be suppressed, thus preventing its co-deposition with Al on the cathode. This development is therefore anticipated to inform the development of electrorefining processes to obtain high-quality recycled Al for numerous manufacturing applications.