Comparative studies on CO2 adsorption performance of different morphologies of Silicalite-1 zeolites synthesized from fly ash

Abstract

Solid waste fly ash has a great impact on the environment and pollutes water, air and soil to different degrees. Therefore, it is of great significance to realize the high-value utilization of fly ash. In this paper, high purity SiO₂ was successfully extracted from fly ash by high temperature calcination, alkali fusion activation and pickling, and then different morphologies of Silicalite-1 zeolites were synthesized by using SiO₂ extracted from fly ash as silicon source, TPAOH as templating agent and NaOH as alkali source. The influencing factors such as crystallization time, crystallization temperature, NaOH dosage, TPAOH dosage and different hydrosilica ratios were investigated separately. The results show that under the conditions of crystallization time of 12 h, crystallization temperature of 180 ℃ and molar ratio of water-silicon of 42, the prepared P-S (plate-like Silicalite-1) has good morphology, high relative crystallinity and adsorption capacity of CO₂ of 1.89 mmol/g. The CO₂ adsorption capacity of the S-S (spherical-like Silicalite-1) prepared by adjusting the amount of TPAOH is 1.34 mmol/g. The CO₂ adsorption capacity of the prepared C-S (cross-type Na-Silicalite-1) is only 1.06 mmol/g. The CO₂ adsorption capacities follow P-S > S-S > C-S. The results may provide a valuable reference for zeolite-based adsorbents in the adsorption removal or recovery of CO₂.