Abstract: Zeolite Y, P and HS were synthesized hydrothermally from flyash which has a higher SiO₂/Al₂O₃ ratio. The influence of alkali’s activation conditions, including baking method, alkalinity and NaOH/flyash mass ratio on synthetic zeolite was investigated. XRD analysis shows that the type, granularity and relative content of synthetic zeolite were affected by these factors. Baking in a short time twice at 620℃ can improve activation effect. And zeolite P was synthesized in lower alkalinity and NaOH/flyash mass ratio condition, while zeolite HS was synthesized in higher alkalinity and NaOH/flyash mass ratio condition. The synthetic condition of zeolite Y was between them. The synthetic products have high crystallinity, purity and cation exchange capability.

Key words: fly-ash, zeolite, alkali activation, granularity, cation exchange capability