Reaction of acid activated montmorillonites with hexadecyl trimethylammonium bromide solution

Acid-activated montmorillonites (AMt) prepared at different acid\montmorillonite ratios were reacted with hexadecyl trimethylammonium (C16TMA) bromide solution. The acid treated Mt incorporated smaller amounts of the surfactants than the parent Mt, due to the reduction of the cation exchange capacity after acid-treatment. The powder X-ray diffraction patterns exhibited a similar basal spacing of 3.80 nm but with less ordered structure at higher acid\montmorillonite ratios. A certain degree of conformational heterogeneity was observed by 13C CP\NMR spectroscopy due to the different local environment of C16TMA+ ions in the interlayer space. The in-situ PXRD patterns showed an increase of the basal spacing of organo acid-activated montmorillonites when heated at intermediate temperatures (100-200 °C), while the basal spacing was almost constant in this range of temperature for the organomontmorillonite. Generally, the stability of the surfactant decreased when intercalated into the montmorillonites compared to the pure C16TMABr. This fact implies that the interlayer space influences the decomposition steps. © 2008 Elsevier B.V. All rights reserved.