The Ordering of Cetylpyridinium Bromide on Vermiculite

P. G. Slade, M. Raupach and W. W. Emerson
Division of Soils, C.S.I.R.O., Adelaide, Australia

Abstract: X-ray superlattice reflections, infrared spectroscopy, and chemical analyses have established that cetylpyridinium bromide (CPB) is highly ordered when adsorbed on vermiculite. The molecules, which stand at about 57° to the silicate surface, form close-packed arrays. Full surface coverage is achieved only for the most highly charged vermiculites. The packing within the arrays accounted for the superlattice observed and each adsorbed molecule had an area of 18.4 Å2 at the surface. The implications of these findings for the CPB method used in soil surface area studies are discussed.

Key Words: Adsorption • Cetylpyridinium • Exchange • Interlayer • Superlattice • Vermiculite

Clays and Clay Minerals; April 1978 v. 26; no. 2; p. 125-134; DOI: 10.1346/CCMN.1978.0260207
© 1978, The Clay Minerals Society
Clay Minerals Society (www.clays.org)