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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 FT-IR spectroscopic studies of coal fly ashes, originated from various polish power plants are reported. The results of MIR investigations were compared to the X-ray diffraction (XRD) measurements and chemical analyses. They are mainly composed of silica, alumina and lime. The infrared spectrum in the middle range can be used to describe both the structure of phases present in the fly ash and to identify the characteristic elements of the individual components of ash. The results indicate that the amount of aluminosilicate and its Si/Al ratio induce a shift in the T-O stretching band appearing at 950-1100 cm-1. Moreover, FWHM of these bands indicates the participation of the crystalline phase relative to amorphous. The presence of carbonate phases generates substantial changes in the 1450-1400 cm-1 area of the spectra. The presence of such phases as anhydrite, mullite or illite has also been established on the basis of IR spectra. [ABSTRACT FROM AUTHOR]

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]

[Display omitted] • C-S-H gels in the presence of heavy metal ions have been synthesized. • The effect of heavy metal ions on the structure of silicate gel has been investigated. • The vibrational spectra to describe the structure of C-S-H phase have been used. • XPS showed binding energies of metal ions, clarifying their role in immobilization. • We have attempted to evaluate the mechanism of immobilization of individual ions. This study investigates the immobilization mechanisms of heavy metal ions in the C-S-H phase. Synthetic C-S-H phases were prepared via the precipitation method, incorporating five different ions (Pb(II), Cd(II), Ni(II), Zn(II), and Cr(III)). Structural analysis of the obtained material was conducted using vibrational spectroscopy (both FT-IR and Raman), X-ray photoelectron spectroscopy, and X-ray diffraction. Spectroscopic methods were primarily employed to evaluate the structural effects and polymerization degree of the resulting C-S-H phase. Morphological changes were characterized using scanning and transmission electron microscopy (SEM and TEM, respectively). Our findings reveal several mechanisms for immobilizing heavy metal cations: precipitation of insoluble compounds (particularly notable for Ni(II) and Cr(III)), replacement of Ca(II) ions within the silicate structure (evident in the crystallization of Ca(OH) 2 in samples containing Cd(II), Ni(II), and Zn(II) in minimal quantities), and strong bonding of certain metals (such as Pb(II)) with the C-S-H phase structure. These insights contribute to understanding the potential applications of C-S-H phases in heavy metal immobilization. [ABSTRACT FROM AUTHOR]

Coal fly ash as a secondary aluminosiliceous raw material that is commonly used in the so-called geopolymerization process has been activated with different alkali hydroxides solutions: LiOH, NaOH and KOH. Changes in the aluminosilicate structure of the material during alkali-activation have been analyzed in detail on the basis of ATR/FT-IR spectra. These changes mainly affect both the integral intensity and FWHM of bands in the range of 1200–950 cm −1 , however dehydration and carbonation process can be also analyzed based on obtaining results. [ABSTRACT FROM AUTHOR]

[Display omitted] • We synthesized amorphous aluminosilicate gel in the presence of heavy metal ions. • The effect of heavy metal ions on structure of aluminosilicate gel has been investigated. • We used the vibrational spectra to describe the structure of C-(A)-S-H phase. • We have attempted to evaluate the mechanism of immobilization of individual ions. Calcium aluminosilicate hydrates (C-(A)-S-H) with two different C/S molar ratios of 1.0 and 1.7 were synthesized by precipitation with the use of the alkali-activation method. The samples were synthesized with solutions of heavy metals nitrates such as nickel (Ni), chromium (Cr), cobalt (Co), lead (Pb), and zinc (Zn). Metal cations were added in the amount of Ca:Me equal to 9:1, while Al/Si was 0.05. The influence of the addition of heavy metal cations on the structure of the C-(A-)S-H phase was investigated. For this purpose, XRD was used to examine the phase composition of the samples, FT-IR and Raman spectroscopy were used to determine the effect of heavy metal cations on the structure of the obtained C-(A)-S-H phase and their degree of polymerization. Using SEM and TEM, changes in the morphology of the obtained materials were determined. Possible mechanisms of immobilization of heavy metal cations have been determined. It was found that some heavy metals (Ni, Zn, and Cr) could be immobilized by precipitation of insoluble compounds. On the other hand, they could remove Ca2+ ions from the structure of aluminosilicate and take their place, as evidenced by the crystallization of Ca(OH) 2 in samples with the addition of Cd, but also Ni and Zn in small amounts. A third possibility is the incorporation of heavy metal cations at the silicon and/or aluminum tetrahedral sites, as is the case with Zn. [ABSTRACT FROM AUTHOR]