As a result of its lamellar structure, vermiculite exhibits various properties related to structural features, such as the sheet loading associated with the numerous isomorphic substitutions or the ability to dehydrate and rehydrate. It is an interesting mineral in physics, chemistry and biology and very attractive due to its numerous thermal applications and as an insulator. In addition to water, vermiculite can adsorb inorganic or organic substances in the expandable interlayer. Among the various studies conducted on the intercalation of polar organic molecules by clay minerals, the most studied are those related to the adsorption properties of alcohols (Bergaya et al., 2006).
Two vermiculites from China and Libby were treated with different alcohols (methanol, ethanol, propanol and butanol), at room temperature, for 1 month, and subsequent microwave irradiation, for 20 seconds. This treatment caused structural changes and expansion of the vermiculites. The structural changes were characterized by x-ray diffraction, infrared spectroscopy and scanning electron microscopy. The results indicated: 1) The appearance of extra interstratified phases during the transformation from 2- to 1-WLHS (Water Layer Hydration States); 2) the improvement of the crystallinity and order of the most phases, which are the same phases of the untreated vermiculites or even some more. The expansion, k, was measured by the change of the apparent density (k=density of the raw sample/density of the treated sample) (Justo et al., 1989). Expansion is related to the water loss, composition and distribution of vermiculite cations. Thus, the Fe2+ ions would facilitate the fixation of the K+ ions but not the water, so that the amount would be lower (Marcos and Rodríguez, 2010). The expansion with microwaves irradiation of the samples treated with alcohol varied related to starting sample and time of alcohol treatment. It was also observed that some particles expanded and others did not, as reported previously by Marcos and Rodríguez (2011). The objective of this work was to relate the expansion to structural changes induced in the investigated samples and to the potassium migration.References: