Densification and crystallization of Ba-exchanged zeolite A powders

The effect of thermal treatment, Na content and mineralizer ion on the sintering process of Ba-exchanged zeolite A on the zeolite → celsian thermal transformation are investigated. The powder samples containing different amounts of Na+ and Li+ were pressed at 30 MPa and thermally treated at temperatures from 1000 to 1400 °C for times up to 5 h and subsequently were characterized by room temperature X-ray diffraction and by scanning electron microscopy. Increasing the Na residual content in the Ba-zeolite A samples improves the sintering process, even if the highest Na content appears to inhibit the zeolite → celsian transformation, since a new crystalline phase appears at the highest temperature. Moreover, the porosity of all samples thermally treated is quite high. Finally the manufacture of pressed samples allowed lower temperatures and times to be used to obtain the transformation zeolite Ba-A → monoclinic celsian, which suggests it is a potential method to prepare celsian low temperature refractory materials. At last an ANOVA analysis was carried out to identify the independent parameters from a statistical point of view.