Chapter 13 - NIR Contribution to The Study of Modified Clay Minerals

Abstract

Abstract Clay minerals are abundant, inexpensive and environmentally friendly materials with a huge potential for diverse industrial and environmental applications. Their properties can be considerably modified by mechanical, thermal or chemical handling. Mid infrared spectroscopy (MIR), 4000–400 cm− 1 spectral region, is a useful and widely available tool for the characterization of modified clay materials. In contrast, the utilization of near IR (NIR) spectroscopy (8000–4000 cm− 1) is rather rare despite its benefits, which include the simplicity and non-destructive character of sample preparation. This chapter reviews the potential of NIR spectroscopy to examine the modification of structure and properties of clay minerals. The NIR spectra of selected minerals are analyzed in detail in order to bring new information often not available using MIR spectroscopy. The chapter starts with a presentation of how dry grinding partly destroys clay minerals, providing materials with increased specific surface area (SSA). Further attention is given to the effects of heat treatment, such as layer charge reduction, as well as acid activation in producing materials with increased SSA, porosity and acidity. The different aspects of the interactions of clay minerals with organic species are particularly discussed. The last section is focused on porous clay heterostructures. Each of these processes has been reported in terms of how NIR can assist in the interpretation, evaluation and investigation of new material properties.