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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] • 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]