Hydrothermal Effects on Cesium Sorption and Fixation by Clay Minerals and Shales

Sridhar Komarneni and Della M. Roy
Materials Research Laboratory, The Pennsylvania State University University Park, Pennsylvania 16802

Abstract: The effects of hydrothermal conditions on the sorption and fixation of cesium by various clay minerals and shales were investigated. Hydrothermal heating, which may be expected in a radioactive waste repository, altered the clay minerals and shales and led to a decrease in their cation-exchange capacity. Cesium sorption greatly decreased in micaceous vermiculite and in well-crystallized illites containing vermiculite upon hydrothermal treatment at 400° and 300 bars pressure due to complete layer collapse. However, poorly crystallized illites heated as above showed either a small increase or only a slight decrease in Cs sorption because of partial layer collapse. These studies show that the decrease in Cs sorption is greater in well-crysallized illites than in poorly crystallized illites when treated similarly under hydrothermal conditions. Hydrothermal heating of Cs-sorbed and Cs-saturated samples increased the amount of Cs fixation in all minerals and shales as a result of collapse of the layers. For example, a sample of the Conasauga shale fixed only 18% of sorbed Cs before treatment but fixed 47% after hydrothermal treatment at 200° and 300 bars pressure. Thus, hydrothermal conditions in a shale repository may be beneficial after leaked radioactive Cs ions are taken up by clay minerals in shales.

Key Words: Cesium • Hydrothermal • Illite • Ion fixation • Ion sorption • Shale • Vermiculite • Waste repository

Clays and Clay Minerals; April 1980 v. 28; no. 2; p. 142-148; DOI: 10.1346/CCMN.1980.0280211
© 1980, The Clay Minerals Society
Clay Minerals Society (www.clays.org)