Synthesis of zeolite NaA nano-crystalls; effect of synthesis parameters on crystallinity and crystal size

Hydrothermal synthesis of zeolite NaA crystals with a composition of Al2O3:aSiO2:bNa2O:cH2O was investigated. Effects of SiO2/Al2O3, Na2O/Al2O3, and H2O/Al2O3 ratios, crystallization temperature, and time on crystallinity and crystal size of zeolite NaA crystals were studied. An attempt was made to understand the interactions between these parameters. The crystal species of zeolite NaA were characterized by XRD and SEM. Considering the interactions between these parameters showed that the effects of increasing SiO2/Al2O3 and Na2O/Al2O3 ratios simultaneously neutralized each other so that their overall effect was found to be insignificant. On the other hand, the effects of increasing SiO2/Al2O3 and H2O/Al2O3 ratios reinforced each other and significantly affected crystallinity and crystal size. Increasing alkalinity increases crystallization rate and reduces synthesis time. Also, effects of increasing crystallization temperature and time simultaneously reinforced each other. The effect of decreasing alkalinity was moderated with that of increasing Na+ content in the synthesis gel.