Effect of Clay Charge on Swelling: A Clay-Modified Electrode Study

Alanah Fitch1, Jia Du1, Huamin Gan2 and J. W. Stucki2
1 Department of Chemistry, Loyola University of Chicago 6525 N. Sheridan Rd., Chicago, Illinois 60626
2 Department of Agronomy, University of Illinois, Champaign-Urbana Urbana, Illinois 61801-4798

Abstract: The uniformity of clay films affects the transport of an anionic electroactive probe through the film. When cations other than Na+ are present in the initial swelling of the film (such as native K+ and Ca2+), or when the native clay is highly charged, internal dislocations of the film, caused by variable stacking domains, enhance the diffusive transport of Fe(CN)63- across the film. This effect is investigated using clay-modified electrodes in which the clays are of variable exchange forms (Na+, Ca2+, or K+) and variable charge. The charge on the clay is determined both by the native form of the clay and by reduction of structural Fe3+. The results suggest that swelling of clays increases in a linear fashion with CEC, at least for minimally charged clays.

Key Words: Charged clays • Diffusive transport • Iron reduction

Clays and Clay Minerals; October 1995 v. 43; no. 5; p. 607-614; DOI: 10.1346/CCMN.1995.0430510
© 1995, The Clay Minerals Society
Clay Minerals Society (www.clays.org)