4SEIDEL A, SLUSZNV A, SHELEF G, ZIM MELS Y. Variation in fly ash properties with milling and acid leaching[J]. Fuel, 2005, 84(1): 89-96.
5PARK H C, PARK Y J. Synthesis of alumina from high purity alum derived from coal fly ash[J]. Materials Science and Engineering A, 2004, A367: 166-170.
6MATJIE R H, BUNT J R, van HEERDEN. Extraction of alumina from coal fly ash generated from a selected low rank bituminous South African coal[J]. Minerals Engineering, 2005, 18(3): 299-310.