Electrolytic Recovery of Aluminum from 1-Butyl-3-methylimidazolium Bis(trifluoromethanesulfonyl)imide Ionic Liquid Containing AlCl3

Electrolytic recovery of pure aluminum is a conventional method for the recycling of waste aluminum alloys, which is very important to economic development and environmental protection. However, the conventional electrolytic recovery process suffers from several inherent problems, which restricts the further development of this technology. In this study, an air- and moisture-stable 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ionic liquid was applied in the dissolution of aluminum chloride. The upper phase of the resulting mixture was used as a low-temperature electrolyte in the electrolytic recovery of pure aluminum. The results of cyclic voltammetry and linear sweep voltammetry showed that aluminum could be electrodeposited from the electrolyte and that the main impurity elements of the aluminum alloy could also be stripped off by the electrolytic method. Based on these measurements, the electrolytic recovery process was conducted at 0.2-0.6 V and 303.2-373.2 K. Scanning electron microscope micrographs showed that smooth, compact and well-adherent deposits were obtained at 0.4 V from 303.2 to 323.2 K. In this situation, the preferred crystallographic orientation of these deposits was the (200) plane. Meanwhile, the mass content of aluminum in all deposits was higher than 99.6% according to the purity characterization. This study may be useful for the further application of ionic liquids in the low-temperature recycling of waste aluminum alloys.