Thermal Behavior of Hydrotalcite and of Anion-Exchanged Forms of Hydrotalcite

G. W. Brindley and S. Kikkawa1
Mineral Sciences Building, The Pennsylvania State University University Park, Pennsylvania 16802
1Present address: Institute of Scientific and Industrial Research, Osaka University, Yamadakami, Suita, Osaka 565, Japan.

Abstract: Chloride-, sulfate-, and perchlorate-exchanged forms of hydrotalcite have been prepared and their layer spacings determined after equilibration in hydrous atmospheres and after heat-treatments up to the temperature of decomposition in the range 300–400°C. The initial carbonate form of hydrotalcite and also brucite, for purposes of comparison, have been similarly studied. Only chloride-hydrotalcite and brucite exhibit a single phase stable to the decomposition temperature. The other anionic forms exhibit various phases with different layer spacings which are interpreted in terms of the size, orientation, and stability of the anions and, in some cases, the presence of additional water. A regularly interstratified form of sulfate-hydrotalcite (layer spacing = 19.80 Å) is obtained at room temperature and relative humidity <50%; at higher humidities, a fully hydrated phase is obtained, and at 50°C a collapsed form is obtained. In the preparation of perchlorate-hydrotalcite, an interstratified phase (layer spacing = 17.0 Å) was recognized with alternating carbonate and perchlorate layers, although the evidence is less certain.

Key Words: Anion exchange • Brucite • Hydrotalcite • Interstratification • Perchlorate • Thermal reaction

Clays and Clay Minerals; April 1980 v. 28; no. 2; p. 87-91; DOI: 10.1346/CCMN.1980.0280202
© 1980, The Clay Minerals Society
Clay Minerals Society (www.clays.org)