Effect of grinding on the preparation of porous materials by acid-leached vermiculite

Abstract

This study examines the effect of grinding on the textural properties of the materials prepared by selective acid-leaching of vermiculite. The clay mineral used was the < 80 μ m fraction of vermiculite from Santa Olalla (Spain). The acidic attack was carried out on the original and ground samples (2 and 4 min) using HCl solutions of several concentrations at 80 °C. Although grinding had a scarce influence on the porous properties of the original vermiculite, it strongly affected the reactivity to the leaching treatment. Thus, the residue of the unground vermiculite treated with 1 M HCl had a specific surface area of 504 m 2 g - 1 , while for the sample ground for 4 min and treated with the same acid concentration, the residue had a specific surface of 720 m 2 g - 1 . Additionally, the residue in the non-ground sample retains some vermiculite phase, while it is totally destroyed in the ground sample. Formation of micropores during treatment contributes to the increase of surface area. Grinding favors the formation of porous materials and the synthesis of amorphous silica after acid treatment.