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Amorphous natural silicoaluminates, such as expanded perlite, transform themselves in three-dimensional crystalline species, exhibiting effects of the alkaline solutions with NaCl. In this paper the kinetics and the effect of the reaction conditions over the crystallization process are studied.Na(OH) solutions 15%, 18%, and 20 % w/v, and NaCl solutions from 0 % up to 30 % w/v were used. Temperature range was from 80ºC to 95 ºC.  The effect of the solid/liquid relationship and the fluid dynamic conditions were studied.  The rate of the zeolite formation process depends on the concentration of Na(OH) / NaCl solutions and on the reaction temperatures.The fluid dynamic conditions and the solid/liquid relationships have no effect over the crystallization process in the studied range. The effect of the NaCl is to increase the reaction rate independently of the kind of obtained zeolite, which is associated with the relationship Si/Al.Powder X  ray diffraction (XRD) analysis and scanning electron microscopic (SEM) were employed to study the zeolite formation process in order to elucidate the mode of zeolite crystallization.The mechanism implies the formation of units of nuclei of growth, and the population of these units is controlled by NaCl concentrations. The nucleation and growth Avrami model properly describes the process of formation of the crystalline species. It is found that the parameters k and n are linked respectively with the conditions and the reaction mechanism.

Zeolite Formation from Expanded Perlite Using Hydrothermal Treatment with Alkaline Solutions of NaCl: A Kinetic Study of the Process