THERMODYNAMICS PROSESS OF MICA DEHYDROXYLATION
Physical essence dehydroxylation mechanism, which takes place in the preparation of composite materials based on mica, is not fully disclosed, and requires study. Heating natural mica leads to changes associated with the removal of the interlayer space is not only the molecular water (dehydration) and hydroxyl ions (dehydroxylation). Laws of sorption phenomena for which the detailed aspects of mineral laminates such as muscovite and phlogopite are considered in this work are determined by the equilibrium between mica and its hydrate. In this case, the position of equilibrium reactions, characterized by the value of the equilibrium constant, and according to the equation Van’t Hoff, depends on the temperature. Hydroxylate number as the number of water formed from hydroxyl ions within the structure of aluminum-silicon tetrahedron as a function of temperature. The functional dependence of the equilibrium constant on temperature is determined by the change in the Gibbs free energy, which, in turn, causes the equilibrium position dehydroxylate reaction. It is believed that any given temperature corresponds one definite value equilibrium pressure. The speed of reaction is higher during heating and reducing the partial pressure of water vapor that can serve as one of the controlled parameters in the study of the kinetics dehydroxylation process. It is important that the largest reactions equilibrium constants can be judged on the amount of water formed and degidroksilata. It is shown that the process dehydroxylation of phlogopite occurs at a temperature of 180–220?°С C higher than that of muscovite. At temperatures up to 800?°С substantially completed the removal of molecular water and the above process starts 800?°С dehydroxylation limiting step and a proton shift from one hydroxyl group to another to form water and its transfer on to the edges of tetrahedral channels mica. Muscovite for removing water in the temperature range of 700–900?°С in the kinetic regime occurs, as evidenced by a high value of the activation energy of 122 kJ / mol. The temperature dependence of the rate constant dehydroxylation studied mica.