Zeolite A was calcined at 200, 400, 600, 800 and 1000 °C for 2h to evaluate its thermal stability. The zeolite A was synthesized using kaolin waste from kaolin processing industries for paper coating located in the Amazon region. Both zeolite A and further calcined products were characterized by X-ray diffraction analysis and scanning electron microscopy. The zeolite A structure remained stable up to 600 °C, where only small variations in peak intensities were observed. At 800 °C the diffraction pattern still exhibited zeolite A but with the absence of some peaks. At 1000 °C nepheline, mullite and probably sodalite were formed. The zeolite A was also heated at 900 and 950 °C to check the two exothermic peaks observed in the DTA curve. The X-ray diffraction analysis indicated the presence of nepheline, sodalite and mullite.
kaolin waste; zeolite A; thermal stability
