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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., Brzine rasta kristala zeolita A i X mjerene su tijekom kristalizacije pri 80 °C iz amorfnoga alumosilikatnoga prekursora dispergiranoga u 1,4 M otopini NaOH koja je sadržavala različite količine otopljenoga NaAlO2 ili Na2SiO3. Tijek kristalizacije i frakcije zeolita A i X u produktima kristalizacije značajno ovise o sastavu tekuće faze kristalizacijskoga sustava. Analizom promjena koncentracija aluminija, cAl i silicija, cSi u tekućoj fazi te veličine Lm, najvećih kristala zeolita A i X tijekom kristalizacije, utvr|eno je da je brzina rasta kristala neovisna o njihovoj veličini te da se rast kristala odvija reakcijom monomernih i/ili niskomolekularnih aluminatnih, silikatnih i alumosilikatnih aniona iz tekuće faze na površini rastućih kristala zeolita. Utjecaj sastava tekuće faze kristalizacijskih sustava na tijek procesa kristalizacije i brzinu rasta kristala zeolita A i X razmatran je u odnosu na moguće raspodjele aluminatnih, silikatnih i alumosilikatnih aniona u tekućoj fazi.

Changes of the concentrations of aluminium, cAl, and of Silicon, cSi, in the liquid phase as well as of the dimension, Lm, of the largest crystals were measured during crystallization of zeolite A from the amorphous aluminosilicate precursor (1.03 Na2O ⋅ Al2O3 ⋅ 2.38 SiO2 ⋅ 1.66 H2O) dispersed in alkaline Solutions (1.2 or 1.4 M NaOH solution) containing or not containing dissolved Al2O3 and/or SiO2 of appropriate concentrations. Analysis of the relationship between the concentration factors f(c) = f(cAl,cSi) relevant to different growth models and the growth rate of zeolite A crystals have shown 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, and hence that the kinetics of the growth rate of zeolite A crystals may be expressed as: dL/dtc = kg[cAl - cAl(eq)][cSi - cSi(eq)] = kgf(c) , where tc is the time of crystallization, cAl(eq) and cSi(eq) are the aluminium and Silicon concentrations in the liquid phase, corresponding to the solubility of zeolite A under given crystallization conditions, and kg is the rate constant of the linear growth of zeolite A crystals.

Changes of the concentrations of aluminium, cAl, and of Silicon, cSi, in the liquid phase as well as of the dimension, Lm, of the largest crystals were measured during crystallization of zeolite A from the amorphous aluminosilicate precursor (1.03 Na2O ⋅ Al2O3 ⋅ 2.38 SiO2 ⋅ 1.66 H2O) dispersed in alkaline Solutions (1.2 or 1.4 M NaOH solution) containing or not containing dissolved Al2O3 and/or SiO2 of appropriate concentrations. Analysis of the relationship between the concentration factors f(c) = f(cAl,cSi) relevant to different growth models and the growth rate of zeolite A crystals have shown 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, and hence that the kinetics of the growth rate of zeolite A crystals may be expressed as: dL/dtc = kg[cAl - cAl(eq)][cSi - cSi(eq)] = kgf(c) , where tc is the time of crystallization, cAl(eq) and cSi(eq) are the aluminium and Silicon concentrations in the liquid phase, corresponding to the solubility of zeolite A under given crystallization conditions, and kg is the rate constant of the linear growth of zeolite A crystals.