In this study, the silicon and aluminum in fly ash was activated by fusion with sodium carbonate. The fused product was treated by a method involving a desilicification and hydrothermal process. From the supersaturated silicon and aluminum extracted from fly ash, different pure zeolites were synthesized. The structure-directing agents and crystal seeds made a promoting effect on the type of crystallization achieved. The zeolites were characterized in terms of mineralogical composition and cation exchange capacity (CEC). The results showed that the pure zeolites exhibited high CEC ranged from 3.2 to 4.6 meq/g, and the yield ratio reached to 70%. (c) 2007 Elsevier Ltd. All rights reserved.