Abstract:

Ammonium aluminum sulfate hydroxide［NH₄Al(SO₄)₂·12H₂O］, the precursor of Al₂O₃, was prepared with the method of sintering, leaching and adjusting the pH value by using fly ash and ammonium sulfate as raw materials.High-purity alumina was prepared by calcining NH₄Al(SO₄)₂·12H₂O.The effects of the temperature and time of sintering, molar ratio of(NH₄)₂SO₄ vs the Al₂O₃ in fly ash and the grain size of fly ash on the extraction efficiency of Al₂O₃ from fly ash were studied.The efficiency of Al₂O₃ extraction could reach 95.6 percent under the optimum conditions.The purity of the Al₂O₃ from calcining NH₄Al(SO₄)₂·12H₂O that was refined by recrystallization was higher than 99.9 percent.