Synthesis of Zeolite 4A from Kaolin and Bauxite by Alkaline Fusion at Low Temperature

Zeolite 4A was synthesized by fusion method using kaolin and bauxite as raw materials. It comprised alkaline fusion followed by hydrothermal treatment with step-change of synthesis temperature. The synthesized zeolite 4A samples were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and their calcium ion exchange capacity were tested by ethylene diamine tetraacetic acid (EDTA) volumetric method. The influence on the quality of zeolite 4A was investigated under different fusion temperature, fusion time, and mole ratio of SiO2/Al2O3, Na2O/SiO2 and H2O/Na2O. The optimum reaction parameters were determined. The results showed that the reasonable fusion temperature and time should be 600°C and 2 h, and the reasonable ratios of raw materials were the SiO2/Al2O3 ratios from 1.8 to 2.2, the Na2O/SiO2 ratios from 2.0 to 2.3, and the H2O/Na2O ratio at 60, respectively.