Structural and physicochemical properties of natural zeolites: clinoptilolite and mordenite

Natural, H-form and Pd-containing clinoptilolite and mordenite were characterized using adsorption, AFM, FTIR, and TG–DTA methods. The initial natural adsorbents have small specific surface area which increases significantly after their modification. FTIR spectra show the presence of the same typical bands in natural and H-form zeolites. However, the spectra of Pd-including clinoptilolite have a band of ammonia at ν = 1449 cm−1, which can be associated with its adsorption complexes with palladium. The TG data show the presence of several types of water, and larger amounts of water desorb from H-forms of both zeolites up to 120 °C that can be caused by stronger changes in the zeolite structure. However, the zeolite skeleton does not change after acidic processing. The changes are more visible for treated clinoptilolite.