CHARACTERIZATION, SURFACE-AREA, AND POROSITY ANALYSES OF THE SOLIDS OBTAINED BY ACID LEACHING OF A SAPONITE

New deposits of saponite have been described recently in the Madrid Ba sin (Madrid and Toledo provinces, Central Spain), a zone very rich in Mg silicates, especially in sepiolite. This is the first time that the high surface area saponitic material from Yunclillos deposit (Toledo province) is described. The acid treatment of this material with dilut ed solutions of HCl (0.62 and 1.25% by weight) at 25 degrees C for 2, 6, 24, and 48 h has been carried out. Although the conditions employed in the leaching are very soft, most of the octahedral sheet of the cl ay is dissolved, as indicated by the high removal of Mg cations and co rroborated by the changes observed in the FT-IR spectra and by the sim plification in the profile of the TGA-DTA curves of the solids obtaine d after the treatments. The destruction of the saponite structure by t he treatments results in the generation of free silica. The surface ar ea of natural saponite (161 m(2) g(-1)) is doubled in the leached soli ds, even under the mild conditions considered, reaching a maximum valu e of 392 m(2) g(-1). The texture of the free silica generated after th e saponite ordered structure affects the properties of the activated s olids, as shown by the numerical analyses of the nitrogen adsorption-d esorption isotherms of these solids, mainly made by using the ''t'' an d ''f'' plots.