Clean and efficient recovery of aluminum from aluminum-silicon alloy scrap by electrorefining using AlCl3-urea deep eutectic solvent

Abstract

The upcycling of aluminum–silicon alloy scrap by electrorefining in AlCl₃-urea DES at near room temperature was studied. The electrochemical behavior of impurity metals and aluminum was analyzed using the measurement of polarization curves. The result showed that the anodic dissolution of Al, Mn, Zn, Pb, Cu, Fe, Ni, and Si occurred at 0, 0.03, 0.21, 0.27, 0.60, 0.65, 0.87, and 1.65 V (vs. Al(Ⅲ)/Al) in AlCl₃-urea DES, indicating that the anodic dissolution potential of metals in aluminum–silicon alloy in AlCl₃-urea DES was in the order of Al > Mn > Zn > Pb > Cu > Fe > Ni > Si, different from the traditional metal activity series. This result also implied that aluminum was selectively dissolved from the aluminum–silicon alloy anode, whereas the impurity metals remained in the anode by controlling electrolytic potential. The influence of electrolytic parameters, such as electrolysis temperature and current density, on the electrorefining process and effect were studied. The purity of aluminum deposits was more than or equal to 99.5 %, and their microstructure ranged from particles to flower-like microspheres. The cathode current efficiency was approximately 87.8 % and the energy consumption was approximately 2.14 kW·h·kg⁻¹-Al under the optimum conditions of electrolysis temperature 333 K and the current density 5 mA·cm⁻². The process is energy efficient and produces aluminum with the purity comparable to that of primary aluminum. A real sustainability in the aluminum cycle is achieved through the application of this efficient and clean process.