Phase Transformations of α-Alumina Made from Waste Aluminum via a Precipitation Technique

We report on a recycling project in which alpha-Al2O3 was produced from aluminum cans because no such work has been reported in literature. Heated aluminum cans were mixed with 8.0 M of H2SO4 solution to form an Al-2(SO4)(3) solution. The Al2(SO4) 3 salt was contained in a white semi-liquid solution with excess H2SO4; some unreacted aluminum pieces were also present. The solution was filtered and mixed with ethanol in a ratio of 2:3, to form a white solid of Al-2(SO4)(3)center dot 18H(2)O. The Al-2(SO4)(3)center dot 18H(2)O was calcined in an electrical furnace for 3 h at temperatures of 400-1400 degrees C. The heating and cooling rates were 10 degrees C /min. XRD was used to investigate the phase changes at different temperatures and XRF was used to determine the elemental composition in the alumina produced. A series of different alumina compositions, made by repeated dehydration and desulfonation of the Al-2(SO4)(3)center dot 18H(2)O, is reported. All transitional alumina phases produced at low temperatures were converted to alpha-Al2O3 at high temperatures. The X-ray diffraction results indicated that the alpha-Al2O3 phase was realized when the calcination temperature was at 1200 degrees C or higher.