Surface Properties of Smectites Exchanged with Mono- and Biprotonated 1,4-Diazobicyclo(2,2,2)-Octane

L. Van Leemput1, M. S. Stul, A. Maes, J. B. Uytterhoeven and A. Cremers
Centrum voor Oppervlaktescheikunde en Colloïdale Scheikunde de Croylaan 42, B-3030 Leuven (Heverlee), Belgium
1 Present address: Janssen Pharmaceutica, 2340 Beerse, Belgium.

Abstract: Smectites exchanged to various degrees with mono- or biprotonated 1,4-diazobicyclo(2,2,2)- octane (Dabco) have a porous structure in which the organic molecule acts as a “pillar.” Less Dabco2+ than Dabco1+ was necessary both to initiate and to complete expansion, whereas for both Dabco1+ and Dabco2+ the threshold for expansion increased with the charge density of the clay. Interstratification of 9.7-Å and 14.5-Å (Dabco1+) or 14.1-Å (Dabco2+) layers was observed before full expansion occurred.

Nitrogen sorption isotherms on partially exchanged Dabco1+- and Dabco2+-clays are of the BET II and Langmuir type respectively, whereas n-butane adsorbed according to BET type II for both cationic forms. The specific surface area was governed by the number of Dabcoz+ pillars, irrespective of the inorganic cation, and increased with Dabcoz+ content even beyond the composition where full expansion was reached and notwithstanding the increasing number of silicate layers in the c direction of the crystal units. This relationship is explained by an enhanced random interleaving of clay platelets in the stacking units containing Dabcoz+.

Key Words • Dabco • Interlayering • Pillar • Smectite • Surface area

Clays and Clay Minerals; August 1983 v. 31; no. 4; p. 261-268; DOI: 10.1346/CCMN.1983.0310403
© 1983, The Clay Minerals Society
Clay Minerals Society (www.clays.org)