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

Abstract In this work 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 and crystallization temperature and time were studied on crystallinity and crystal size of zeolite NaA crystals. It was tried 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 effects of increasing SiO2/Al2O3 and Na2O/Al2O3 ratios simultaneously neutralize each other so that their overall effect is not significant. On the other hand, the effects of increasing SiO2/Al2O3 and H2O/Al2O3 ratios reinforce each other and significantly affect crystallinity and crystal size. Increasing alkalinity increases crystallization rate and reduces synthesis time. Also, effects of increasing crystallization temperature and time simultaneously reinforce the effects of each other. The effect of decreasing alkalinity is moderated with that of increasing Na+ content in the synthesis gel.