FT-IR signatures of TNT on montmorillonite-clay particles

2,4,6-Trinitrotoluene (TNT) has a number of specific properties that make it a nearly ideal explosive for military applications. It is relatively stable with respect to non desired detonation, easy to store and handle and has a high explosive power. A broad variety of landmines contain TNT as the main explosive charge. There are several methods currently used to detect buried landmines, both physically and chemically. The goal of this work is develop new methods for detecting TNT in contact with soil, based on Chemical Point Detection methodologies. FT-IR spectroscopy is used to provide information about identity and composition of compounds in very small samples or small heterogeneities in large samples. The main objective of this work is to study the vibrational behavior of TNT when in contact with soil that contains argillaceous minerals, specifically of the group of the smectites. Literature indicates that clays of this group present certain characteristics leading to affinity to nitroaromatic compounds, such as TNT. The clay used in this investigation was saturated with potassium cations to increase the adsorption of TNT on clay. The study includes the exposure of Clay/TNT mixtures to a series of environmental variables, which include: variation of alkalinity and acid content of the mixtures, variation of temperature, addition of water and explosive mass fraction in the mixture. Visible changes of color in the K-clay-TNT or Na-clay-TNT mixtures were observed but without displaying vibrational changes in highly basic clays.