Porous structure of a sepiolite as deduced from the adsorption of N2, CO2, NH3 and H2O

The micropore volume and non-microporous surface area of a sepiolite, heat treated in air at 110 degreesC and 500 degreesC have been evaluated by application of the BET and Dubinin-Radushkevich equations to the adsorption isotherms of gases with different polarity, The surface area is a function of the adsorptive used as a consequence of specific adsorbent-adsorbate interactions. However, the volume of micropores is very similar for all adsorptives. On the other hand, the results suggest that the main active site governing the hydrophilic behavior of sepiolite are the four water molecules coordinated to magnesium. Their elimination changes the behavior of sepiolite to essentially hydrophobic. (C) 2001 Published by Elsevier Science B.V.