Thermal dehydration kinetic mechanism of Mn1.8Co0.1Mg0.1P2O7·2H2O using Málek's equations and thermodynamic functions determination

Abstract

Abstract Mn1.8Co0.1Mg0.1P2O7·2H2O was synthesized via hydrothermal method and the thermal dehydration product was confirmed to be Mn1.8Co0.1Mg0.1P2O7. The thermogravimetry/differential thermogravimetry/differential thermal analysis, Fourier transform infrared, atomic absorption spectrophotometry, X-ray diffraction and scanning electron microscopy techniques were employed for sample characterization. Non-isothermal kinetics was studied under air atmosphere at four heating rates and the single thermal dehydration process was observed. Iterative Kissinger–Akahira–Sunose equation was used to calculate the apparent activation energy Eα values. Dehydration process was confirmed to be a single-step kinetic process with the unique kinetic triplets. Malek's equations were used to determine the kinetic model f(α) and pre-exponential factor A. Sestak–Berggren model was suggested to be the mechanism function for the dehydration process. The best fit led to the kinetic triplets of Eα=(79.97±6.51) kJ/mol, ln A=16.83 and f(α)=α0.520(1–α)1.255 (α is the extent of conversion). The thermodynamic functions of activation were calculated using activated complex theory together with A value.