The role of charcoal on DTA curves of organo-clay complexes: an overview

DTA of organo-clay complexes supplemented by other thermal analysis methods supplies information on the thermal reactions, properties and stability of the complex, the amount and properties of the adsorbed water in the organo-clay and on the bonding between the organic species and the clay. It is used to identify the mineral to differentiate between various complexes composed of the same clay and the same organic ligand and to establish their composition. During the gradual heating in oxidizing atmospheres the adsorbed organic material is oxidized, giving rise to significant exothermic peaks. DTA curves of organo-clays are divided into three regions: (1) the dehydration of the clay, (2) the thermal oxidation of the organic material and (3) the dehydroxylation of the clay. The exothermic oxidation reaction occurring during the gradual heating of the sample takes place in two steps, in the range 200–500 °C, oxidation of organic hydrogen and formation of water and charcoal, and 400–750 °C, oxidation of charcoal and formation of CO₂. The exothermic peak temperatures depend on the mineral and on the organic compound and on the types of bonding between these two components of the organo-clay complex. The present communication concentrates in the role of the combustion of charcoal in the study of the fine structure of the complex and of the type of associations between the organic compound and the clay.