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The results of vibrational spectroscopy studies of zeolites synthesized from expanded perlite using hydrothermal method were presented. The starting material used was a waste obtained during the production of expanded perlite. The effects of synthesis temperature and time, as well as NaOH concentration and solid to liquid ratio on the obtained products were determined. The resulting materials were analyzed regarding phase composition. In particular, the structures of materials were examined using FT-IR spectroscopy in the middle and far infrared ranges as well as Raman spectroscopy. The results were compared to the XRD and XRF measurements, as well as SEM observations. It has been found that by using a sufficiently high concentration of NaOH, it is possible to efficiently synthesize zeolite at temperatures above 50 °C. The presence of zeolite phase was confirmed by the measurement of spectra. Pseudolattice range, i.e. 800-400 cm -1 , was analyzed in detail. In this range, bands associated with the ring vibrations occur. They are characteristic for secondary building units (SBU) existing in zeolite structure. Depending on time, temperature and NaOH concentration, zeolite X, A, Na-P1 and hydroxysodalite have been identified as synthesis products in autogenous pressure. [ABSTRACT FROM AUTHOR]

This work presents the results of spectroscopic (MIR and Raman) studies of zeolite structures after immobilization of heavy metal cations from aqueous solutions. The sorption of Ag +, Cu 2+, Cd 2+, Pb 2+, Zn 2+, and Cr 3+ ions has been conducted on zeolites belonging to different structural groups, i.e., sodium forms of natural chabazite, mordenite, ferrierite, and clinoptilolite, as well as on synthetic zeolite Y. Systematic changes in intensities and positions of the bands corresponding to the characteristic ring vibrations have been observed in the measured spectra. The most visible changes are observed in the FT-IR spectra of the samples in the range of 850–450 cm –1, and in the Raman spectra in the range of 600–250 cm –1. Depending on the zeolite structure, the bands, which can be regarded as a kind of indicator of ion exchange, were indentifi ed. For example, in the case of IR spectra, these bands are at 766, 703, 648, 578, and 506 cm –1 for zeolite Y, at 733 and 560 cm –1 for mordenite, at 675 cm –1 for clinoptilolite, etc. The degree of changes depends on both the type of cation and its concentration in the initial solution. This is connected with the way of binding of metal ions to the zeolite aluminosilicate framework, i.e., a proportion of the ion exchange and chemisorption in the process. Cations mainly undergoing ion exchange, such as Cd 2+ or Pb 2+, have the greatest impact on the character of the spectra. On the other hand, Cr 3+ ions practically do not modify the spectra of zeolites. Results of IR and Raman spectroscopic studies have been compared with those obtained by atomic absorption spectroscopy (AAS), from which the proportion of ion exchange to chemisorption in the process and the effective cation exchange capacity of the individual samples have been estimated. [ABSTRACT FROM AUTHOR]

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]