THE STUDY OF DEHYDRATION OF COLEMANITE IN NON-ISOTHERMAL CONDITIONS

The regularities of colemanite dehydration under non-isothermal conditions are investigated. It is established that colemanite, supplied to the Russian Federation from Turkey, has calcite in its composition. The chemical composition of colemanite is determined using the X-ray fluorescence analysis method. It is shown that the processes of dehydration of colemanite under non-isothermal conditions at a heating rate of 10 °С / min are accompanied by two endothermic effects at 660,7 K and 675,7 K with a total mass loss of 17,3 %. The rate of mass loss of colemanite from the temperature at heating up to 773 K, at which colemanite dehydrates and passes into the amorphous phase, is also studied. The regularities of changes in the rate of dehydration of colemanite are established. It is shown that the maximum values of the dehydration rate of colemanite are observed in the temperature range of 653–678 K. The activation energy of colemanite dehydration is determined to be 86,000 J/mol. Based on the experimentally obtained data, the rate constant of the colemanite dehydration process is calculated. The process of dehydration of colemanite is adequately described by the formal equation of kinetics. Most of the kinetic curve is adequately described by the resulting kinetic equation. It is proposed to describe the mechanism of dehydration of colemanite by a two-stage process, accompanied at the first stage by the removal of crystallization water, and at the second stage-by the removal of hydroxyl groups