Effect of ionic solutions on clay minerals crystal chemistry.

This work describes the basic structural features, the origin and properties of clay minerals and of interstratified clays in order to outline the kinetics of structural changes induced by clay-water and clay- ionic solutions interactions. The role of layer charge is discussed because it is recognized as one of the most important features of 2:1 phyllosilicates that produce the mineral ability to retain cations and to adsorb water and various polar molecules. Sample preparation techniques in order to obtain a representative clay-mineral for structural X-ray analysis, such as chemical pre-treatment and preparation of oriented clay mineral aggregates was also considered. A special focus was devoted to water-bearing clay minerals. In 2:1 layer and in 1:1 structures water occurs in interlayer positions and forms complexes with interlayer cations which are affected by P-T and chemical environmental conditions. Some examples of polluted environment remediation were reported in order to enhance clay mineral properties as barrier in environmental pollution.