Adsorption of 1-butanol from water on modified silicate surfaces

The structure and the sorption properties of partially hydrophobized silicates (dodecylammonium and dodecyldiammonium vermiculites) have been investigated in aqueous solutions of 1-butanol. The alcohol is preferentially adsorbed on the surface. The interlayer composition is calculated from adsorption and x-ray diffraction data. In air-dried state the organic cations lie flat on the interlamellar surface. In aqueous butanol solutions, the basal spacing of dodecylammonium vermiculite gradually increases with the extent of butanol adsorption because the chains increasingly point away from the surface. The basal spacing of dodecyldiammonium vermiculite is virtually independent on the interlayer composition because the expansion of the interlayer space is sterically restricted and a relatively rigid structure is formed. The enthalpy of the displacement of water by 1-butanol has been determined by flow sorption microcalorimetry. The displacement process is endothermic.