Low temperature phase changes in montmorillonite and nontronite at high water contents and high salt contents

Abstract

Prior work has revealed the existence of one or more low temperature phase changes in clay water systems in the temperature range −20°C to about −50°C. The number and the temperatures at which these phase changes appear seems to be associated with the type of exchangeable ion(s) and the number and nature of individual water domains present. In this paper, we report the results of low temperature differential calorimetry on montmorillonite and nontronite clays at high water and high salt contents. The presence of electrolytes at high concentration is shown to have a very marked effect. The low temperature phase changes are completely absent at high electrolyte concentrations in these clay water systems. The presence of electrolytes also was observed to have a distinctive effect on the shape of the initial freezing peak associated with ice segregation.