Abstract
The kinetics of synthesis of zeolites Na-A and Na-X from fused South African class F coal fly ash were studied by using an ultrasound device as a real-time, in-situ diagnostic tool. Ex-situ techniques, for example XRD, ICP, and SEM, were used to complement the results of the kinetic study. Reaction rate, reaction order, and activation energy of crystallization processes in clear solution extracted from fused fly ash were calculated on the basis of ultrasound signal data recorded at different crystallization temperatures. Zeolite Na-X and zeolite Na-A crystals were both obtained without ageing. The zeolite Na-X sample showed contaminations of zeolite P and sodalite depending on the synthesis temperature. For zeolite Na-A the impact of ageing on the process of formation was also studied.