Effect of ultrasound on preparation of porous materials from vermiculite

High- and low-charge vermiculites from Spain (Santa Olalla and Ojen) were sonicated in an ultrasonic liquid processor to produce changes in particle size, morphology and structural ordering. The ultimate aim of this treatment was to prepare 18 A Al-pillared vermiculites. Sonication caused a rise of the S-BET from the initial value 1 m(2) g(-1) of the raw samples to 36 and 54 m2 g(-1) for the Santa Olalla and Ojen samples, respectively. The XRD study shows that the crystal structure of both minerals remains practically unchanged by sonication. However, the 001 diffraction broadens due to a significant delamination process, yielding values of particle thickness of 185 and 260 angstrom for the low- and high-charged vermiculites, respectively. The sonicated Santa Olalla sample (high-charge) treated with Al-13 solution shows a d(001) powder diffraction peak at 14 angstrom, whereas the sonicated Ojen sample (low-charge) shows peaks at 14 and 18 angstrom. The 18 angstrom diffraction peak is preserved at high temperatures (550 degrees C) and it is responsible of an increase of surface area and microporosity. The ultrasound treatment of low-charge vermiculite from Ojen is a new method for obtaining 18 angstrom Al-pillared vermiculites. The ultrasound treatment using H2O2 in the medium produces a significant delamination and a decrease of the particle size and the layer charge leading to the Al-polymer intercalation. (c) 2005 Elsevier B.V All rights reserved.