Recycling of aluminum metal matrix composite using ionic liquids: Effect of process variables on current efficiency and deposit characteristics

Recycling of aluminum metal matrix composite via electrolysis in ionic liquids at low-temperature was investigated. The electrolytic melt comprised of 1-butyl-3-methylimidazolium chloride (BMIC) and anhydrous AICl(3). Aluminum metal matrix composite (Duralcan((R)), Al-380, 20 vol.% SiC) was electrochemically dissolved at the anode, and pure aluminum (> 98%) was deposited on a copper cathode. The influence of experimental parameters such as concentration of electrolyte and applied cell voltage on the efficiency of aluminum metal matrix composite recycling was studied at 103 +/- 2 degrees C. High applied voltages and concentration of AlCl3 yielded high current densities. Current densities obtained during this process were in the range of 200-500A/m(2) and current efficiencies in the range of 70-90%. The deposits were characterized by scanning electron microscope, X-ray diffractometer, mass spectrometer, and atomic absorption spectrophotometer. Characteristics of the deposited microstructure ranging from columnar to spherical were obtained. Energy consumption was in the range of 3.2-6.7 kWh/kg-Al for the experimental conditions studied. The optimum conditions obtained in the present investigation for maximum current efficiency and least energy consumption with uniform deposit microstructure were low applied voltage and intermediate electrolyte concentration. Low energy consumption and no emission of pollutants are the two main advantages of this process compared to the current recycling processes. (c) 2004 Elsevier Ltd. All rights reserved.