Method for preparation of sodium metasilicate pentahydrate by fly ash

The invention discloses a method for the preparation of sodium metasilicate pentahydrate by fly ash, which comprises the steps: using sodium hydroxide solution to alkaline-hydrolyze sodium silicate solution with the silicon dioxide preparation modulus of 0.4-0.8 in the fly ash, carbonizing amorphous hydrated silicon dioxide with the partial sodium hydroxide solution, then re-dissolving the amorphous hydrated silicon dioxide with the sodium hydroxide solution to formulate crystallization solution with the ratio of SiO2 to Na2O of 1:0.8-1.2, removing suspended matters by filtration, heating andconcentration, cooling and crystallizing, and performing solid-liquid separation at 35 DEG C to result in sodium metasilicate pentahydrate. The method has the advantages of simple process, inexpensive raw material, great easiness for industrialization and tremendous economical and environmental benefits.