Study of the adsorption of organic molecules on clay minerals by differential thermal analysis

Abstract

DTA was adapted to study the types of associations between water molecules, exchangeable metallic cations and organic molecules or ions formed on clay surfaces. Comparison between curves recorded in the absence or presence of air show that in the latter case strong diagnostic exothermic peaks are obtained and the analysis is more sensitive for identification of the different associations. The location of the peaks serves to differentiate between adsorbed and non-adsorbed organic matter, a neutral free organic molecule, cationic organic matter or a neutral molecule coordinated to transition metal. DTA study of the adsorption of aliphatic and aromatic amines by montmorillonite is described in detail, in order to demonstrate how this technique is applicable for the study of surface reactions.