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As a continuation of our previous study, in this work, we investigated the effects of propanol and butanol treatments and subsequent irradiation with microwave on commercial vermiculites. No expansibility was observed after propanol or butanol treatments (k = 1.0). Samples treated with propanol or butanol and subsequently irradiated with microwaves expanded in a similar manner as they did with methanol and ethanol. The results of X-ray diffraction (XRD), thermogravimetric analysis (TG and DTA), scanning electron microscopy (SEM) and infrared spectroscopy indicated structural changes as: 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, due to migration of potassium. [ABSTRACT FROM AUTHOR]

Present work reports the alcohol treatment and subsequent irradiation with microwave of commercial vermiculites. Alcohol treatment resulted in slight delamination of the layers and the color of the samples changed into brilliant golden and no expansibility was observed (k ≤ 1.3). Samples treated with alcohol and subsequently irradiated with microwaves expanded; the greater expansibility (k = 8 for 1 h) was provided by the most complex sample and treated with methanol. The structural changes were studied by using X-ray diffraction (XRD), thermogravimetric analysis (TG and DTA), infrared spectroscopy and carbon analysis. The results of these analysis indicated dehydration-hydration and order–disorder which would be related to the entry of alcohol into the vermiculites and the loss of water content. The changes occurred in a similar way to the temperature and vacuum, and were less pronounced for the purest vermiculite. The crystallite size and lattice strain values which reflect changes in crystallinity and structural order varied slightly regardless of treatment and time. Alcohol treatment and subsequent microwave irradiation may be the procedure for obtaining purest vermiculite from less pure sample. [ABSTRACT FROM AUTHOR]

Abstract: For the purpose of knowing the vermiculites which would have larger capability to retain contaminating substances heating commercial samples from different places have been identified and their thermal behaviour at several temperatures has been investigated by X-ray diffraction (XRD), electron microprobe, thermal analysis (TG and DTA), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The commercial vermiculites can be divided into two types: type 1 (Sta. Olalla, Piauí and Goiás) with Mg2+ and K+ (<1) as the principal cations in the interlayer space, and type 2 (China E, China W, China G and Palabora) with K+ (approximately=or >1) and/or Na+ and/or Ca2+ with or without Mg2+ as the principal interlayer cations. The process of dehydration in situ with the temperature seems restricted to interlamellar water monolayers of 1-WLHS type-1 of vermiculites, without dehydration to a zero-water-layer-hydration state (0-WLHS) and the dehydroxylation starts at lower temperatures than in vermiculites of type 2. The maximum hydration state exhibited by the type-2 samples at ambient temperature was equal or lower than the monolayer hydrate, the dehydration process in situ with the temperature was slower and the dehydrated vermiculite coexists with a mica-like structure. The behaviour of vermiculites at elevated temperature examined in situ can be understood considering that the vermiculites constitute a complex system not necessarily in equilibrium and where kinetics plays an important role. Commercial vermiculites heated abruptly at 1000 °C during 1 min transform to mica-like or mica-like coexisting with enstatite, in contrast to the purest Sta. Olalla vermiculite, with only magnesium interlayer cations, which changes to enstatite. [Copyright &y& Elsevier]