STRUCTURE OF INTERCALATED CLAY MINERALS

Daniel Janeba¹, Pavla Capkova¹, Zdenek Weiss², Henk Schenk³

¹Faculty of Mathematics and Physics, Charles University, Ke Karlovu 3, 121 16 Praha 2, Czech Republic, janeba@karlov.mff.cuni.cz,
²Central Analytical Laboratory, Technical University of Ostrava, 708 33 Ostrava - Poruba, Czech Republic,
³Laboratory for Crystallography, University of Amsterdam, Nieuwe Achtergracht 166, 1018 WV Amsterdam, The Netherlands

Keywords: intercalation, clay, montmorillonite, XRD profile analysis, molecular modeling

Intercalated clay minerals attract the attention of scientists as they can be used as sorbents of organic pollutants from water environment, they are studied from the environmental point of view, because they can help to explain the retention and transport of heavy metal atoms or radioactive waste in the nature. In recent years organic molecules are intercalated into smectites and these intercalates have different photophysical and photochemical properties. In all these cases the information about the structure obtained from the powder pattern (the single crystal is usually not available) is limited (due to the disordered structure of intercalated clays) to the determination of basal spacing. Basal spacing is a very important characteristic of layered intercalates but does not include the information about the porosity, possible interlayer space, position and orientation of the guest species or bonding. That is why the additional information comes from spectroscopic methods and also molecular modeling. Especially molecular modeling can tell more about the position and orientation of the intercalant in the interlayer about the host-guest and guest-guest interaction.

As a result of a complex studies of structures of intercalated clays the structure analysis following from the combination of X-ray diffraction experiments and molecular mechanics simulations (performed in the modeling environment Cerius²) will be presented. The investigated materials were montmorillonite intercalated with Al-hydroxy polymers, heavy metals (represented by Zn²⁺ and Cd²⁺ cations) and organic molecules (tetramethylammonium and trimethylphenylammonium). The present structure analysis has been focused to following problems: position and orientation of intercalating species with respect to the silicate layers, their ordering in the interlayer space, the anchoring of the intercalant to the layers and stacking of layers. In all cases the results from powder pattern are in a very good agreement with the result from molecular modeling [1,2,3,4].

[1] P. Capková, R.A.J. Driessen, H. Schenk., Z. Weiss, J.Mol.Model. 3(1997), 467-472
[2] D. Janeba, P. Capková, H. Schenk, Clay Miner., 33(1998), 197-204
[3] Z. Weiss, Z. Klika, P. Capková, D. Janeba, S. Kozubová, Physics and Chemistry of Minerals (1998), in press
[4] D. Janeba, P. Capková, Z. Weiss, J.Mol.Model.(1998), in press