Croatica Chemica Acta, Vol. 78 No. 1, 2005.
Original scientific paper
Influence of the Concentrations of Aluminium and Silicon in the Liquid Phase on the Growth Kinetics of Zeolite A and X Microcrystals
Sanja Bosnar
Josip Bronic
Ivan Krznarić
Boris Subotić
Abstract
Kinetics of the crystal growth of zeolites A and X was measured during their crystallization, at 80 °C, from an amorphous aluminosilicate precursor dispersed in a 1.4 M NaOH solution containing different amounts of dissolved NaAlO2 or Na2SiO3. The crystallization pathway and fractions of zeolites A and X in the crystalline end product strongly depend on the composition of the liquid phase of the crystallizing system. Analyses of the changes of the concentrations of aluminum, cAl, and of silicon, cSi, in the liquid phase as well as of the dimension, Lm, of the largest crystals of zeolites A and X during crystallization, have shown that the growth rate of zeolite A crystals is size-independent, and that the growth is governed by the reaction of monomeric and/or low-molecular aluminate, silicate and aluminosilicate anions from the liquid phase on the surfaces of growing zeolite crystals. Influence of the composition of the liquid phase of the crystallizing system on the course of crystallization process and on the growth rates of zeolite A and zeolite X crystals are discussed in terms of the possible distribution of aluminate, silicate and/or aluminosilicate anions in the liquid phase.
Keywords
zeolite A; zeolite X; aluminate; silicate; crystallization; crystal growth
Hrčak ID:
2659
URI
Publication date:
24.3.2005.
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