Synthesis of Zeolite A from Mongolian Coal Fly Ash by Hydrothermal Treatment

摘要

Raw coal fly ash and acid pretreated fly ash were used to synthesize A-type zeolite by hydrothermal treatment. Acid pretreatment was used to reduce calcium and iron contents of the raw fly ash. In order to synthesize zeolite A an aqueous gel adjusted to a molar composition of Na_2O:Al_2O_3:1.926SiO_2:128H_2O was utilized. After hydrothermal treatment, several types of zeolites were formed: zeolite A, analcime, faujasite and hydroxy-sodalite. The highest content of zeolite A was formed in the mixture treated at 80°C for 8 hours. Fly ash and zeolitic products were characterized by SEM, XRF, XRD and cation exchange capacity (CEC). CEC values of the zeolitic products were 28-38 times higher than those found in raw fly ash. Acid pretreatment which leads to low calcium and iron content, is the preferable method for processing fly ash for zeolite synthesis. Synthesized zeolite can be used for ion exchanger in water treatment.