Kinetics and Mechanism of Thermal Dehydration of KMnPO4•H2O in a Nitrogen Atmosphere

The potassium manganese phosphate monohydrate (KMnPO4 center dot H2O) was confirmed to dehydrate in a single step process. Therefore, the thermal transformation of this compound is an ideal case for testing the kinetic models and calculation procedures. The kinetics of thermal dehydration of this compound was studied using thermogravimetry (TG) at four heating rates by Ozawa and KAS methods. The calculated activation energy values from both methods are very close to each other. Four calculation procedures based on a single TG curve and the isoconversional method, as well as 26 mechanism functions were carried out. The mechanism function of dehydration with the integral form g(alpha) = 1 (1 - alpha)(1/3) and the differential form f(alpha) = 3(1 - alpha)(2/3) can be suggested to be the mechanism of phase boundary reaction (spherical symmetry) for the title compound. In this work, the kinetic parameters and the transition state thermodynamic functions for the dehydration process of KMnPO4 center dot H2O are reported for the first time.