In the present paper, dehydration kinetics of zeolite Na-A synthesized from fly ash was investigated by means of thermogravimetric analysis. Na-A zeolite was formed from coal fly fash by fusion with sodium hydroxide and succeeding hydrothermal treatment at 100degreesC after induction period. The model-free kinetic method was applied to calculate the activation energy of the dehydration process of fly ash-based zeolite as a function of conversion and temperature. The Vyazovkin model-free kinetic method also enabled the definition of time, necessary to remove water molecules from the zeolite structure for a given temperature. (C) 2003 Elsevier B.V. All rights reserved.