VENEZUELAN NATURAL ALUMOSILICATES AS A FEEDSTOCK IN THE SYNTHESIS OF ZEOLITE-A

Zeolite A has been synthesized from low-cost natural aluminosilicates. The samples were characterized by X-ray powder diffraction, chemical a nalysis, electron microscopy, FTi.r. spectroscopy, and nitrogen adsorp tion. Studies of calcination temperature effects and Na2O/SiO2 and H2O /Na2O ratios were performed. It was observed that mineral calcination at temperatures in the range of 500-850-degrees-C led to zeolite A for mation, but when the calcination step was omitted, hydroxysodalite was formed. In samples calcined for 5 h at temperatures higher than 850-d egrees-C, no zeolite was observed. A maximum in crystallinity was obta ined for samples calcined in the range 700-750-degrees-C. The zeolite crystal mean size increased as the alkalinity increased. I.r. spectros copy was used to characterize the products. An area band ratio at 570 and 470 cm-1 showed a linear correlation with % crystallinity determin ed by XRD.