Synthesis of Zeolite A from Mongolian Coal Fly Ash by Hydrothermal Treatment
Raw coal fly ash and acid pretreated fly ash were used to synthesize A-type zeolite by hydrothermal treatment. In order to synthesize zeolite A an aqueous gel having a molar batch composition of Na2O:Al2O3:1.926SiO2:128H2O was utilized. Fly ash and zeolitic products were characterized by SEM, XRF, XRD and cation exchange capacity (CEC). 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. CEC values of the zeolitic products were 28-38 times higher than that of in raw fly ash. Acid pretreatment which leads to low calcium and iron content is preferable method for processing of fly ash for the zeolite synthesis. Synthesized zeolite can be used for ion exchangers for water treatment.