Layered Mineral Structures and their Application in Advanced Technologies
This volume covers the topics related to the 13th EMU School ‘Layered Mineral Structures and their Application in Advanced Technologies’. All of the selected topics, the school, and this volume are thus aimed at providing an in-depth knowledge of the complex field of layered materials, with an attempt to address several fundamental aspects, which range from crystal chemistry and structure to layer packing disorder, from surface properties to the description of the most advanced experimental techniques useful in the characterization of layered materials. Layered materials, because of their particular atomic arrangement, are commonly characterized by physical and chemical properties of great interest in numerous technological and environmental processes and applications, as better detailed in the body of this volume. Most of these properties play a significant role in Earth sciences, environmental sciences, technology, biotechnology, material sciences and many other scientific areas. The surface properties of layered materials control important interaction processes, such as coagulation, aggregation, sedimentation, filtration, catalysis and ionic transport in porous media. Layered minerals also control many aspects of Earth's rheology, i.e. the movement of geological masses, at least as far down as the lower crust. Given this frameset, it should be no surprise that the extremely large field of investigation of these materials can, and in most of the cases must, be approached from several different viewpoints. However, providing full coverage of the immense literature devoted to all the topics above may be impractical, if not impossible.
The surface properties of clay minerals
Published:January 01, 2011
Robert A. Schoonheydt, Cliff T. Johnston, 2011. "The surface properties of clay minerals", Layered Mineral Structures and their Application in Advanced Technologies, M.F. Brigatti, A. Mottana
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Clay minerals have interlayer surfaces and edge surfaces, the former being the most important, especially in the case of swelling clays or smectites. Water is by far the most important adsorbed molecule in the interlayer space, where it interacts with the exchangeable cations and with the siloxane surface. Transition metal ion complexes are selectively ion-exchanged in the interlayer space of smectites. Polyamine complexes easily lose their axial ligands to adopt a square planar configuration. The more stable and bulky tris(bipyridyl) and tris(phenanthroline) complexes in the interlayer space give chiral clay mineral composites that can be used in columns for chiral chromatography, in asymmetric catalysis and in non-linear optics. The formation of clay mineral-dye complexes is a two-step process: instantaneous adsorption of the dye molecules, mainly as aggregates, followed by a slower redistribution process over the clay-mineral surface. With careful choice of dye molecules, non-linear optical materials can be prepared which exhibit properties such as second harmonic generation and two-photon absorption. Ion exchange of cationic proteins is a three-step process: (1) instantaneous adsorption at the edges; (2) adsorption in the interlayer space, followed by; (3) weak adsorption in excess of the cation exchange capacity. The extent to which these three processes occur depends on (1) the kind of exchangeable cation in the interlayer; and (2) the molecular weight, shape and charge of the protein molecules.