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This contribution presents the results of structural investigations on the cured and high temperatures of three series of geopolymers. The specimens were synthesized at 80 °C from coal fly ash and three activators of variable composition based on sodium hydroxide and sodium silicate solutions. Structural and microstructural analysis was performed, especially using in-situ measurements of XRD patterns and IR spectra as a function of temperature. The cured compounds' phase content and compressive strength changed slightly depending on the starting chemical composition. All analyzed materials experience a mass loss due to water removal at 300 °C, followed by increased porosity from disintegrating compounds above 300 °C. Higher alkali content improves strength (400–600 °C) possibly due to nepheline formation. The amorphous phase gradually softens during heating, influenced by alkali content. Structural analyses were supported by model calculations of a number of aluminosilicate structures. The cluster analysis using the k-means algorithm was used to divide the PCA space into regions that represent structural similarities, and analyzing specific point positions in the space allowed for several conclusions to be drawn about the studied materials, including that changes in chemical composition and thermal treatment can promote the transformation from sodalite to nepheline and that the glass network has elements that are nepheline-like and may promote its crystallization. [ABSTRACT FROM AUTHOR]

In this work, the studies on the formation of zeolites from expanded perlite waste and their use in the sorption process of Cd ions will be reported. Such approach is innovative and has not been investigated elsewhere. The results of the synthesis of zeolites from aluminosilicate waste using hydrothermal method were presented. By-product from the process production of expanded perlite was used as the starting material. Theoretical and practical aspects of Cd ions sorption process onto material synthesized in selected conditions (a material with good sorption capacity can be obtained by 24 h reaction of 1 g of perlite waste in 10 mL of 4.0 M NaOH solution with at 70 °C) will be presented. The atomic absorption spectroscopy has been used as the main method, from which the effective cation exchange capacity as well as the proportion of ion exchange to chemisorption in the sorption process have been determined. Structural analyses of the sample before and after sorption process have been also carried out by the mid-infrared spectra measurement, especially pseudolattice range of the spectra was analyzed in detail in which changes caused by ion exchange of non-tetrahedral ions have been observed. [ABSTRACT FROM AUTHOR]

We present a direct and geometric construction for an invariant measure in Poncelet's porism. [ABSTRACT FROM AUTHOR]

In this work the DFT calculations were carried out by means of Gaussian09 program for chosen model cluster- mor Composite Building Unit of zeolites structures. Vibrational frequencies computations and infrared spectra were obtained subsequently for above model. The results of calculations have been compared with IR (MIR and FIR range) spectroscopic studies of zeolites belonging to 5-1 structural group (mordenite and ferrierite) after heavy metal cations (Ag, Zn, Cd, Pb, and Cr) immobilization. Changes in intensities and positions of the bands corresponding to the characteristic ring and Me-O vibrations have been observed. These rings occur in pseudomolecular complexes (built of [SiO] and [AlO] tetrahedra) which constitute the secondary building units and form zeolite framework. Based on the results of DFT method calculations, normal vibrations of the 5-1 unit 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 (800-500 cm), as well as Me-O vibrations (below 400 cm). It was proven those cations' sorption causes changes in the experimental spectra of zeolites. Sorption has been conducted on monoionic forms of mordenite and ferrierite. Based on the results of the sorption/desorption experiments, the proportion of ion-exchange to chemisorption in the process and the effective cation exchange capacity of the individual samples have been estimated. Results of AAS studies have been compared with those obtained by vibrational (IR and Raman) spectroscopy. Changes in intensities and positions of the bands corresponding to the characteristic ring vibrations, due to the immobilization of heavy metal ions, have been observed. [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]