Kinetic aspects of the thermal treatment of acid crystallohydrate, MgHPO<inf>4</inf> · 3H<inf>2</inf>O. Part 2. Dehydration and accompanying effects

Abstract

Dehydration of MgHPO4·3H2O takes place in the temperature interval from 120° C to 250° C. Continuous water loss in a wide temperature range results in the formation of MgHPO4 at 250 °C. Dehydration was studied under non-isothermal conditions, using differential scanning calorimetry (DSC). The reaction kinetics were followed by making a number of DSC patterns at different heating rates. Activation energy was found to be 144 kJ mol-1 by the Kissinger method and 149 kJ mol-1 by the Ozawa method. The order of reaction was 0.7. Dehydration increases disorder of the system, changes the actual symmetry of PO4 groups and causes breakdown of the crystal structure. © 1987.