Influence of synthesis parameters on NaA zeolite crystals

The influences of the crystallization temperature, time, and alkalinity of the reaction system and aluminum sources (aluminum chloride and aluminum sulfate) on the synthesis of NaA zeolite have been systematically investigated using the dry-gel conversion method (DGC). The phase and morphology of the synthesis products were characterized using X-ray diffraction and SEM, respectively. This study showed that the alkalinity and temperature affected the NaA zeolite crystallization process and the size distribution of the crystalline end products. Furthermore, as the reaction time increased, the metastable phase transformed into a more stable phase. It was worth mentioning that the final NaA zeolite product contained a small quantity of NaX zeolite when aluminum chloride was used as the aluminum source while using aluminum sulfate as the aluminum source, the final product was mostly sodalite, indicating that the anions in the different aluminum sources have a significant effect on the crystallization process, most likely due to their electrostatic and steric interactions with the zeolite framework. To obtain NaA zeolite crystals with uniform sizes and high crystallinity, the optimal synthesis parameters for the two aluminum sources were determined.