Dynamic and controlled rate thermal analysis of attapulgite

Abstract

The thermal decomposition of the clay mineral attapulgite has been studied using a combination of dynamic and controlled rate thermal analysis. In the dynamic experiment two dehydration steps are observed over the 20–114 and 114–201°C temperature range. In the dynamic experiment three dehydroxylation steps are observed over the temperature ranges 201–337, 337–638 and 638–982°C. The CRTA technology enables the separation of the thermal decomposition steps. Calculations show the amount of water in the attapulgite mineral is variable. Dehydration in the CRTA experiment occurs as quasi-isothermal equilibria. Dehydroxylation occurs as a series of non-isothermal decomposition steps. CRTA technology offers better resolution and a more detailed interpretation of the decomposition processes of a clay mineral such as attapulgite via approaching equilibrium conditions of decomposition through the elimination of the slow transfer of heat to the sample as a controlling parameter on the process of decomposition. Constant-rate decomposition processes of non-isothermal nature reveal partial collapse of the layers of attapulgite as the attapulgite is converted to an anhydride.