Model Calculation of Sepiolite Surface Areas

Toshiyuki Hibino1, Atsumu Tsunashima1, Atsushi Yamazaki2 and Ryohei Otsuka2
1 Materials Processing Department, National Institute for Resources and Environment 16-3 Onogawa, Tsukuba, 305 Japan
2 Department of Mineral Resources Engineering, School of Science and Engineering, Waseda University, 3-4-1 Ohkubo, Shinjyuku, 169 Japan

Abstract: In general, the N2-BET surface areas of sepiolite samples range from 95 to 400 m2/g depending on deposits.

The surface areas of five sepiolites, all varying in crystallite size, were measured on heating, and were compared with a model calculation. A sharp decrease in the surface area, due to crystal folding, was observed between 200° and 400°C. Both before and after the folding, each sepiolite sample had peculiar values. Our model sufficiently explains this difference in surface areas among the samples. In the model, which is based on the Brauner-Preisinger structural model, surface area is a function of the crystallite size and the ratios of the coverage for nitrogen adsorption on both the internal and external surfaces. These ratios of the coverage can be inversely estimated from the model. The ratios of the coverage on the internal surface are less than 0.19, and that on the external surface between 0.7 and 1.0.

Key Words: Heat treatment • Model calculation • Sepiolite • Surface area

Clays and Clay Minerals; August 1995 v. 43; no. 4; p. 391-396; DOI: 10.1346/CCMN.1995.0430401
© 1995, The Clay Minerals Society
Clay Minerals Society (www.clays.org)