Synthesis of NaA zeolite used as adsorbent from kaolin

摘要

Zeolite NaA was successfully synthesized by hydrothermal method using kaolin as a combined source for silica and alumina. In this work, zeolite NaA with high static water adsorption was synthesized from the low-cost raw material kaolin and the reaction parameters were optimized. Metakaolin was obtained by calcining kaolin at temperatures ranged from 953 K to 1173 K. The synthesis mixture was pre-crystallized at 343 K and crystallized at 373 K successively. Zeolite NaA was obtained, which was confirmed by SEM, XRD and the water adsorption analysis. The optimized metakaolinization temperature was found at 973 K. The influence of Na2O/SiO2 molar ratio 、pre-crystallization time and seed on the crystallization of NaA zeolite was investigated. A thorough mixing of metakaolin and NaOH solution was favourable for the nucleation/crystallization rate. The obtained NaA zeolite under the optimized conditions without any seed showed an excellent crystallinity and static water adsorption of 28.0 wt.%, which was higher than 25.9 wt.% of the commercial NaA zeolite. Kaolin was suggested to be a feasible and economical raw material for practical industrial application of NaA zeolite.