Dehydration and re-hydration of the zeolites with 4-4-1 SBU's: near IR evidence for topological changes in heulandite I

Near-IR diffuse reflectance spectra show the absence of hydroxyls in natural heulandite and the presence of hydroxyls in its heat-collapsed phases B and I. These results, compared with analogous ones of barrerite and stellerite, indicated the impossibility for a framework, which has been interrupted by heat-induced dehydration, to re-form by rehydration the original topol. of the natural phase. In general, there was a direct correlation between the amt. of new T-O-T bridges and the mobility of the new framework in zeolites built by connecting 4-4-1 secondary building units.