Vacuum Thermal Stability and Textural Properties of Attapulgite

Summary Evolution of the external surface area and the two types of microporosity of attapulgite (structural and inter-fiber) were examined as a function of a vacuum thermal treatment upt to 500°C. The methods used include: controlled transformation rate thermal analysis, N 2 and Ar low temperature adsorption calorimetry, water vapor adsorption gravimetry and quasi equilibrium gas adsorption procedure of N 2 at 77K and CO 2 at 273 and 293K. Depending on the outgassing conditions, i.e. the residual pressure, the structure folds 150 to 70°C. For lower temperature, only a part (18%) of the structural microporosity is available to N 2 , 13% to argon and 100% to CO 2 . With water, the structure can rehydrate after the structure is folded up to an outgassing temperature of 225°C.