Abstract
Waste sandstone cake, which is discharged as industrial waste, was converted into crystalline zeolite-X using alkali fusion. The cake was transformed into a soluble phase via alkali fusion, and then agitated in distilled water at room temperature to give an intermediate solid, followed by synthesis at 80°C to give the final product. The effects of the agitation and synthesis times on the product phase were investigated with a view to obtaining a single crystalline zeolite-X. Hydroxysodalite was synthesized from the intermediate solid obtained without agitation, and with increasing agitation times for the intermediate solid, the amount of zeolite-X in the product increased, because of the increased Si content in the intermediate solid and the decrease of interference from impurities in the synthesis of zeolite crystals. The observed concentrations of Si and Al in the solution during the reaction explain the crystallization of the zeolite phase. The equilibrium adsorption capacity of the product for Sr2+ was almost the same as that of commercial zeolite-X in a low concentration Sr2+ solution, and the maximum adsorption capacity of the product, calculated using the Langmuir isotherm model, was 0.46 mmol/g.
