In-situ ultrasound study of the kinetics of formation of zeolites Na–A and Na–X from coal fly ash
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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.
KeywordsIn-situ Ultrasound Coal fly ash Kinetics Zeolite Na–A Zeolite Na–X
This work was conducted at the University of Erlangen–Nurnberg, Germany, as a supplement of the PhD thesis of N. Musyoka. The authors would like to thank DAAD and the German Research Foundation (DFG) for funding, and the University of Erlangen–Nuremberg, Germany, for hosting N. Musyoka during his DAAD short-term scholarship in the research group of Professor W. Schwieger (Chair of Chemical Reaction Engineering). We are also grateful to R. Müller for ICP analysis and gratefully acknowledge L. Petrik from the University of the Western Cape, South Africa, for providing the coal fly ash used in this study.
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