engleski

Dissolution of Zeolites NaA, Potassium Exchanged Zeolite (KA) and the Amorphous and Crystalline Phases Obtained by Thermal Treatment of Zeolite KA in Hot Alkaline Solution

Dissolution of zeolites NaA (sodium form of zeolite A), KA (potassium exchanged zeolite A), and the solids K-as (amorphous aluminosilicate obtained by heating of zeolite KA at 962 C for 30 min) and kk (mixture of kalsilite and kaliophilite obtained by heating of zeolite KA at 962 C for 180 min) in 2 M NaOH solution at 70 C was investigated by different methods such as X-ray diffractometry, Fourier transform infrared spectroscopy, scanning-electron microscopy, single point nitrogen absorption, diffrential thermogravimetry, measurement of particle size distribution, and chemical analysis of both the solid and the liquid phase at various stages of the dissolution process. While dissolution of zeolite NaA and starting dissolution of zeolite KA occured in accordance with previously developed model of dissolution, dissolution of the solids K-as and kk occured in two stages; rapid dissolution of a thin (sub)surface layer and slower dissolution of bulk particles followed by solution mediated transformation of the solids K-as and kk into zeolite NaA. The observed differences in the dissolution behavior are explained in the terms of structural characteristics of the investigated solids.

Zeolite NaA; Zeolite KA; Amorphous phase; Crystalline phase; Dissolution; Kinetics

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