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Abstract: The work describes results of spectroscopic studies (MIR, FIR and Raman) of zeolites on which sorption of various metal cations, namely Pb2+, Cd2+, Cr3+, Zn2+, Cu2+ and Ag+ has been carried out. Sorption has been performed on sodium forms of natural zeolites (clinoptilolites from various sources) using aqueous solutions of the metals studied. Changes in intensities and positions of the pseudolattice bands corresponding to ring vibrations have been observed in the measured spectra. Pseudolattice bands are located in the range of ca. 400–700cm−1. The degree of changes depends on both, the type of the cation sorbed and the extent of deformation of zeolite ring units. This, in turn, is connected with the way of metal ions binding to aluminosilicate framework of the zeolite, i.e. the proportion of ion exchange and chemisorption in the process. Results of spectroscopic studies have been compared with those obtained by atomic absorption spectrometry (AAS). [Copyright &y& Elsevier]

Abstract: Vibrational spectra have been applied to study the spatial framework of the zeolites containing double 4- and 6-membered rings as characteristic structural units. Using ab initio methods, theoretical vibrational spectra of isolated D4R and D6R units have been calculated. All the units have been terminated by different cations, i.e. K+, Na+ and Zn2+ to balance their negative charge. Based on the results of calculations, normal vibrations of the units have been visualized and the characteristic ring- or pore-opening vibrations, occurring in these units, have been identified. The effect of cation substitution in terminal positions and Al→Si substitution in tetrahedral positions on the obtained spectra shape has been analyzed. The studied D4R and D6R units constitute the model of secondary building units (SBU) of two important structural zeolite groups. Therefore, the obtained theoretical results have been applied to interpret experimental MIR, FIR and Raman spectra of selected zeolites. In particular, vibrational spectra of zeolite A (LTA), whose structure is composed exclusively of spatially connected D4R units have been analyzed. Spectra of LTA, which was subjected to ion exchange process, have been compared to complete the interpretation procedure. [Copyright &y& Elsevier]

Abstract: Calculated vibrational spectra of aluminosilicate D4R and D6R structural units have been derived using ab initio methods. These units constitute the models of secondary building units (SBU) of two important structural zeolite groups. In the calculations, the model of isolated double four- and six-membered rings containing both AlO4 and SiO4 tetrahedra has been used. Based on the results of calculations, normal vibrations of the units have been visualized. This has enabled us to identify the bands in the spectra obtained. In particular, distinguishment of the characteristic ring or pore-opening vibrations occurring in these units has been possible. The effect of Al→Si substitution in tetrahedral positions on the spectra shape has been also analysed. The calculated results obtained have been applied to interpret experimental spectra of selected zeolites. Their frameworks are formed by spatial connection of structural units in three directions. For the interpretation, the spectra of zeolites whose structure is exclusively composed by the connection of the structural units studied have been chosen. [Copyright &y& Elsevier]

This study investigated the effect of alkali activation process conditions on the IR spectra, on which amount and types of zeolites in the resultant geopolymers influence significantly. Kaolinite was used as starting materials. The kaolinitic clay was first calcined to transform into the amorphous aluminosilicate phases (metakaolinite) and then activated with sodium silicate (as water glass) and sodium hydroxide. The effects of reaction systems composition (expressed as SiO 2 /Al 2 O 3 and Al 2 O 3 /Na 2 O molar ratios) as well as synthesis temperature on the phase composition of obtained products have been determined. In particular, the structures of materials were examined using FT-IR spectroscopy in the middle infrared range. The results were compared to the XRD measurements, as well as SEM observations. Alkali-activation treatment of the metakaolin yielded bulk materials with different amounts and types of zeolite, which reveal the IR spectra of received materials. With proper selection of the initial conditions (temperature and composition), it is possible to obtain a solid material containing zeolite phase such as zeolite X, zeolite A or sodalite. The presence of zeolite phase was confirmed by the measurement of spectra in the middle infrared. In particular in pseudolattice range of the spectra, i.e. 800–400 cm −1 , there are bands associated with the ring vibrations, which are characteristic for secondary building units (SBU) occurred in zeolite structure. IR spectroscopy is also useful in the studies of resulting amorphous phase structure. [ABSTRACT FROM AUTHOR]