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This work presents results of FT-IR spectroscopic studies of anions-chromate, phosphate and arsenate - sorbed from aqueous solutions (different concentrations of anions) on zeolites. The sorption has been conducted on natural zeolites from different structural groups, i.e. chabazite, mordenite, ferrierite and clinoptilolite. The Na-forms of sorbents were exchanged with hexadecyltrimethylammonium cations (HDTMA+) and organo-zeolites were obtained. External cation exchange capacities (ECEC) of organo-zeolites were measured. Their values are 17mmol/100g for chabazite, 4mmol/100g for mordenite and ferrierite and 10mmol/100g for clinoptilolite. The used initial inputs of HDTMA correspond to 100% and 200% ECEC of the minerals. Organo-modificated sorbents were subsequently used for immobilization of mentioned anions. It was proven that aforementioned anions' sorption causes changes in IR spectra of the HDTMA-zeolites. These alterations are dependent on the kind of anions that were sorbed. In all cases, variations are due to bands corresponding to the characteristic Si-O(Si,Al) vibrations (occurring in alumino- and silicooxygen tetrahedra building spatial framework of zeolites). Alkylammonium surfactant vibrations have also been observed. Systematic changes in the spectra connected with the anion concentration in the initial solution have been revealed. The amounts of sorbed CrO42-, AsO43- and PO43- ions were calculated from the difference between their concentrations in solutions before (initial concentration) and after (equilibrium concentration) sorption experiments. Concentrations of anions were determined by spectrophotometric method. [ABSTRACT FROM AUTHOR]

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]

Highlights: [•] We examine the synthesis of zeolites from expanded perlite and fly ash microspheres. [•] It is possible to obtain a coating of sodium zeolites on the light microfillers. [•] We optimized the synthesis temperature, time and NaOH concentration. [•] It is possible to obtain the product in relatively low temperature. [•] We used the infrared spectra to describe the zeolitization progress. [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: This work presents results of FT-IR spectroscopic studies (MIR and FIR range) of zeolites (belonging to D4R and D6R structural groups) after heavy metal cations (Ag+, Cu2+, Cd2+, Pb2+, Zn2+, Ni2+ and Cr3+) immobilization. Sorption has been conducted on monoionic forms of synthetic zeolite A (LTA) and Y (FAU) as well as on natural chabazite (CHA). It was proven that those cations’ sorption causes changes in the spectra of the zeolites. Changes in intensities and positions of the bands corresponding to the characteristic ring and Meons have been observed. These rings occur in pseudomolecular complexes (built of alumino- and silicooxygen tetrahedra) which constitute the secondary building units (SBU) and form spatial framework of the zeolite. Based on the results of DFT method (B98 HF 6–31G(d)) calculations, normal vibrations of the SBU terminated by different cations (Na+, K+) have been visualized. Obtained results have been applied for interpretation of experimental spectra of selected zeolites. The most significant changes have been determined in the region of pseudolattice vibrations (800–550cm−1). On the other hand, an introduction of heavy metal cations into the structure of zeolites has caused the considerable modification of bands due to Meons in FIR spectra (below 400cm−1). In both cases systematic changes connected with the type of cation (its chemical character) have been revealed. Based on changes in the spectra due to immobilization of heavy metal ions, a scale of sorption can be established. [Copyright &y& Elsevier]

Abstract: This work presents the results of FT-IR spectroscopic studies of heavy metal cations (Ag+, Pb2+, Zn2+, Cd2+ and Cr3+) immobilization from aqueous solutions on natural sorbents. The sorption has been conducted on sodium forms of zeolite (clinoptilolite) and clay minerals (mixtures containing mainly montmorillonite and kaolinite) which have been separated from natural Polish deposit. In the next part of the work both sorbents were used to obtain new building composites. It was proven those heavy metal cations’ sorption causes changes in IR spectra of the zeolite and clay minerals. These alterations are dependent on the way the cations were sorbed. In the case of zeolite, variations of the bands corresponding to the characteristic ring vibrations have been observed. These rings occur in pseudomolecular complexes 4–4–1 (built of alumino- and silicooxygen tetrahedra) which constitute the secondary building units (SBU) and form spatial framework of the zeolite. The most significant changes have been determined in the region of pseudolattice vibrations (650–700cm−1). In the instance of clay minerals, changes in the spectra occur at two ranges: 1200–800cm−1 – the range of the bands assigned to asymmetric Si–O(Si,Al) and bending Al–OH vibrations and 3800–3000cm−1 – the range of the bands originating from OH− groups stretching vibrations. Next results indicate possibilities of applying the used natural sorbents for the obtainment of new building materials having favourable composition and valuable properties. The zeolite was used for obtaining autoclaved materials with an addition of CaO, and the clay minerals for ceramic sintered materials with an addition of quartz and clinoptilolite were produced. FT-IR studies were also conducted on the obtained materials. [Copyright &y& Elsevier]

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]