Mössbauer studies of 57Fe in zeolites
Mössbauer spectra of 57 Fe in various zeolites have been obtained. When the iron is exchanged with the cations present in the zeolites as Fe3+, simple two line spectra are found. When attempts were made to introduce Fe2+ into the lattices, complete breakdown of the structure occurred in all zeolites studied except clinoptilolite. However, the spectrum of Fe2+-clinoptilolite showed little evidence of Fe2+ in the structure but considered mainly of the two ferric lines. Valency changes occur readily on dehydrating the various ferric zeolites; either a simple ferrous spectrum was derived or more complicated spectra containing ionic ferric and ferrous states and lines due to covalent ferrous. The original ferric spectra were not reproduced on resorption of water. Filling the channels with water produced more simple ferrous spectra. However, on opening these samples to air, rapid oxidation occurred and the original simple ferric spectra were obtained. Calculations were made to ascertain the site of the ferric ion in Y-zeolite. Although these calculations involved many assumptions best agreement was found for the SII site in this zeolite.