Thermodynamic Properties of Water in Compacted Bentonite Under External Pressure-free Conditions

Abstract

AbstractIn an attempt to determine the thermodynamic properties of water in bentonite, the vapor pressure of water in compacted bentonite was measured as functions of water content and temperature, under external pressure-free conditions. The relative partial molar Gibbs free energy ΔGH2O, enthalpy ΔHH2Oand entropy ΔSH2O of tne waler in bentonite were determined at temperature of 298.15K. The interlayer distance of montmorillonite in bentonite was also measured by X-ray diffraction.It is probable that one fourth of the total water included in the bentonite at water content of 20.3wt% and dry density of 1.76 × 103kg/m3 is nearly free water; the water is not regarded as dilute electrolytic solution but the solution with higher ionic strength. Another one fourth of the water in the bentonite at the water content is bound water; the partial molar entropy of the bound water referred to pure water is from a half to whole of solidification entropy of pure water. The remainder is regarded as intermediately bound water.