| 摘要 |
<p>A method of extracting silica and alumina from fly ash, comprises steps: leaching fly ash with a NaOH solution with a concentration more than 40% by mass, wherein silicon is leached in the form of sodium silicate from the fly ash, thereby obtaining the sodium silicate solution and the alkaline residue with a Al/Si ratio no less than 2; concentrating the resulting sodium silicate solution by evaporation, to obtain sodium silicate solution with a variety of concentrations, or preparing silica by a carbon- decomposing process; preparing Al2O3 by the conventional process from the alkaline residue; and preparing filler or cementfrom the final residue after leaching aluminium. Instead of the idea that alumina is directly leached from the fly ash in the prior art, a process route, wherein silicon is leached at first, and then aluminium is leached, is adopted in said method. Said method can improve the Al/Si ratio in the alkaline residue, simplify process route, and improve the extraction efficiency of the fly ash. Further, said method can be applied for coal gangue with high aluminium content, kaolinite and middle and low grade bauxite, which have been calcined at the temperature of 900°C to 1100°C.</p> |
