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.
Intercalation processes of layered minerals
Published:January 01, 2011
Understanding clay mineral intercalation is the aim of this chapter. Intercalation, which corresponds to a reversible inclusion of different species between two layers, depends on the geometrical, physical and chemical characteristics of each type of clay mineral.
In most phyllosilicates, the interlayer space is occupied by cations which are more or less hydrated. These water molecules which separate two successive layers enable further intercalation reactions by physical adsorption or by chemical grafting of a great variety of species. It is noteworthy that intercalation of inorganic or organic species by ion exchange of these interlayer cations is often the first step in intercalation and is of primary importance in much basic and applied research of the modified clay minerals obtained. This concerns organo-clay minerals (OC), pillared clays (PILC) and clay mineral-polymer nanocomposites (CPN). In non-swelling clay minerals where, generally, the interlayer space is empty, the layers are held by van der Waals interactions or by hydrogen bonds between the stacked layers. In this case, different mechanisms of intercalation can occur and are described.
X-ray diffraction (XRD) and adsorption methods, which induce swelling, and how they are used to confirm intercalation are described below. The meanings of the commonly used terms ‘intercalated’ and ‘exfoliated structures’ in CPN literature and the meanings of the confusing terms, ‘exfoliation’ and ‘delamination’, are also discussed.
When the reversibility of the intercalation can be controlled, applications become possible. In conclusion, this chapter aims to draw attention to the importance of the geo-metrical arrangement of the different clay mineral units in predicting their properties. The unique intercalation property of clay minerals allows us to consider possible further development in aid of our environment, our health and our wellbeing.