ELSEWER May 1997 Materials Letters 31 (1997) 113-l 18 Influence of medium on the properties of boehmite intercalated montmorillonite S. Sivakumar, S.K. Ghosh, A.D. Damodaran, K.G.K. Warrier -’ zyxwvutsrqponmlkj Regional Research Laboratory, Triuandrum 69.5019, India Received 13 September 1996; accepted 18 October 1996 zyxwvutsrqponmlkjihgfedcbaZYXWVUT Abstract Intercalation of boehmite species has been carried out in different media for the preparation of alumina pillared montmorillonite (PILC - pillared clays). The effect of different media such as water, water-isopropanol and water-butanol on the intercalation and thermal stability of the resulting pillared montmorillonite is discussed. Montmorillonite intercalated from different media was characterised by chemical analysis, XRD, BET, TGA and DTA. The d-spacing of the basal planes increased from the initial value of 13 A in montmorillonite to 20-21 A irrespective of the specific medium, whereas upon heating to 700°C the d-spacing decreased to 17-15 A. The minimum reduction of d-spacing is recorded in PILC prepared in water medium. Specific surface area for PILC (water) heated to 300°C is 220 m2/g and is retained at 175 m*/g even after heating to 700°C. In the case of PILC (methanol) the specific surface area is 225 m*/g and 117 m*/g after heating to 300 and 700°C respectively. Further, the surface areas in PILC (isopropanol) and PILC (butanol) are 79 m2/g and 94 m2/g respectively on samples heated at 700°C. These results suggest the influence of different media of intercalation on the thermal stability of the PILC. The solvent present in the interlayer region influences the reorientation of pillars during the dehydroxylation process. The high surface tension of the water-air interface at the interlayer region compared to other solvent-air interfaces in the present study may be able to orient the boehmite species in between the montmorillonite layers to get a homogeneous distribution of pillars and hence high surface area and porosity at higher temperature. Keywords: Montmorillonite; Boehmite; Pillared clays; Intercalation; Surface area 1. Introduction interlayer spacing. The layers get a negative charge Montmorillonite is a hydrated alumina silicate with a two-dimensional layer structure. Each layer is composed of one Al-octahedral sheet sandwitched between two Si-tetrahedral sheets with an interlayer space [l] to make up a unit cell (Fig. 1). The layers are stacked one over the other in the C-direction. The space between the two layers is termed the by the partial substitution of octahedral aluminium with lower valence cations such as Mg*+. The nega- tive charge thus created is balanced by the hydrated cations occupying the interlayer spaces. Swelling and cation exchange properties of these materials make them unique for the intercalation. Exchange of hy- drated cations in the interlayer space by large oligomeric cations, followed by calcination, gives * Corresponding author. metal oxide pillars to open the montmorillonite lay- ers. These permanent porous nanocomposites [2] are 00167-577X/97/$17.00 Copyright 0 1997 Elsevier Science B.V. All rights reserved. PII SO 167- 577X(96)00250- 9