sults showed that after the desilication and alkali dissolution reactions, the leaching rate of alumina reached up to 85%, Al2O3/SiO2 mass ratio decreased in the tailings, as a result the alumina and silica were selectively separated in the desilication reaction, mullite and corundum phases remained unchanged,meanwhile, amorphous aluminosilicate glass was transformed into sodalite phase Na8Al6Si6O24(OH)2(H2O)2, which adhered the ash particle surface, as a result the particle size increased and the particle surface became coarse. After alkali dissolution reaction, mullite and corundum phases were transformed to NaCaHSiO4 and 1.2Na2O?0.8CaO?Al2O3?2SiO2?H2O phases, the particle size decreased. Key words: high-aluminum fly ash; desilication; alkali dissolution; digestion; alumina; phase change
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