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Kinetics and thermodynamic properties of the thermal decomposition of manganese dihydrogenphosphate dihydrate
Author(s)
Date Issued
July 1, 2008
Type
Article
Abstract
The thermal decomposition of manganese dihydrogenphosphate dihydrate Mn(H2PO4)2·2H2O was investigated in air using differential thermal analysis-thermogravimetry. Mn(H2PO4)2·2H2O decomposes in two steps and the final decomposition product (Mn2P 4O12) was studied by X-ray powder diffraction and FT-IR spectroscopy. The activation energies of the dehydration and decomposition steps of Mn(H2PO4)2·2H2O were calculated through the isoconversional methods of Ozawa and Kissinger - Akahira - Sunose and the possible conversion functions have been estimated through the Coats - Redfern method. The activation energy calculated for the dehydration and decomposition of Mn(H2PO4)2·2H 2O by different methods and techniques were found to be consistent. The possible conversion functions of the dehydration and decomposition reactions for Mn(H2PO4)2·2H2O were "cylindrical symmetry" and "three-dimension diffusion", respectively. Activated complex theory has been applied to each step of the reaction and the thermodynamic functions ΔH*, ΔG* and ΔS* are calculated. These values for two stages showed that they are connected with the introduction of heat and are nonspontaneous processes. © 2008 American Chemical Society.
Citation
Journal of Chemical and Engineering Data, 53(7), 1533-1538, 2008