Alkali Fusion-Leaching Method for Comprehensive Processing of Fly Ash

Abstract

Fly ash, composed of mullite, hematite, amorphous silica and quartz, is a promising source for the recovery of alumina and silica. Desilication with help of NaOH and alkali fusion-leaching method and utilization of alumina and silica in the fly ash for preparation of sodalite and silica white were explored in this research. The samples were characterized by using wet chemical analysis and X-ray diffraction. The optimal extraction of SiO2 from Reftinskaya power plant fly ash was 46.2% with leaching at 95∘C for 3 h. Sodalite was synthesized at 200∘C for 1 h followed water leaching at 95∘C for 1 h. Silica white with specific surface area 180-220 m2/g was prepared by carbonation of the Na2SiO3 solution at 40∘C for 90-120 min. The as-prepared silica has a purity of 98,8%. The proposed method is suitable for the comprehensive utilization of the fly ash.