Porous structure of a sepiolite as deduced from the adsorption of N-2, 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 appl ication of the BET and Dubinin-Radushkevich equations to the adsorption iso therms of gases with different polarity, The surface area is a function of the adsorptive used as a consequence of specific adsorbent-adsorbate intera ctions. However, the volume of micropores is very similar for all adsorptiv es. On the other hand, the results suggest that the main active site govern ing the hydrophilic behavior of sepiolite are the four water molecules coor dinated to magnesium. Their elimination changes the behavior of sepiolite t o essentially hydrophobic. (C) 2001 Published by Elsevier Science B.V.