Evaluation of Bound Water Forms in Clays

Abstract

Clays during lithogenesis change the composition, structure and properties, including physicochemical. The result of the thermal analysis was thermograms, on which four peaks of loss of bound water mass were established. These peaks in the author's interpretation are presented as different types of bound water in clays. The obtained experimental data, from the position of the size of the structural elements, allowed to distinguish the following types of water: loosely bound and strongly bound water of the surface of colloids, water surface of crystallites (minerals) and the crystal lattice of minerals. It has been revealed that when the montmorillonite and kaolinite clays are heated, endo-effects are observed in the temperature range up to 900°C caused by the release of H2O and OH-, the source of which is adsorption water and crystal lattice water of minerals. For montmorillonite in the high-temperature range, endo-effects due to the release of CO and CO2 were also noted, which is due to the presence of calcite in its composition. The energy activity of the surfaces of the particles of montmorillonite and kaolinite clays is distributed in the following sequence: the crystallite surface > of the surface of the colloid > of the surface of the strongly bound water of the colloid, which does not contradict the physical nature of the formation of the clay particle. It has been revealed that in montmorillonite clay, the water of the surface of crystallites has the greatest strength of bonds between molecules, the smaller is the strongly bound water of the colloid and the least is loosely bound water of the colloid. In kaolinite clay, the greatest strength of the bonds between molecules is the water of the surface of crystallites, the smaller is the loosely bound water of the colloid and the least strongly bound water of the colloid. In kaolinite and montmorillonite clays, the temperature of the effect and the heat of dehydration of the studied forms of bound water determine the change in the loss of bound water mass in different directions. The results of the studies allowed to quantify various forms of water in clay minerals.