Abstract
Zeolite A has been synthesized from low-cost natural aluminosilicates. The samples were characterized by X-ray powder diffraction, chemical analysis, electron microscopy, FTi.r. spectroscopy, and nitrogen adsorption. Studies of calcination temperature effects and Na 2O SiO 2 and H 2O Na 2O ratios were performed. It was observed that mineral calcination at temperatures in the range of 500–850°C led to zeolite A formation, but when the calcination step was omitted, hydroxysodalite was formed. In samples calcined for 5 h at temperatures higher than 850°C, no zeolite was observed. A maximum in crystallinity was obtained for samples calcined in the range 700–750°C. The zeolite crystal mean size increased as the alkalinity increased. I.r. spectroscopy was used to characterize the products. An area band ratio at 570 and 470 cm −1 showed a linear correlation with % crystallinity determined by XRD.
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