Web Release Date: November 17,
Thermal Decomposition Kinetics of FePO4·3H2O Precursor To Synthetize Spherical Nanoparticles FePO4
and
King Mongkut's Institute of Technology Ladkrabang Chumpon Campus, 17/1 M. 6 Pha Thiew District, Chumphon 86160, Thailand, and Department of Chemistry, Faculty of Science, Khon Kaen University, Khon Kaen 40002, Thailand
Received for review August 14, 2007
Revised manuscript received September 19, 2007
Accepted September 30, 2007
Abstract:
The thermal decomposition of iron phosphate trihydrate FePO4·3H2O was investigated in air using TG-DTG/DTA. The FePO4·3H2O decomposes in two steps, and the final decomposition product (FePO4) was studied
by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared
(FT-IR) spectroscopy. The activation energies of the second dehydration reaction of FePO4·3H2O were
calculated through the isoconversional methods of Ozawa and Kissinger-Akahira-Sunose (KAS), and the
possible conversion functions have been estimated through the Coats-Redfern method. The specificity of
thermal decomposition was characterized by identification of the bonds to be selectively activated due to
energy absorption at the vibrational level, which was assigned by comparing the calculated wavenumbers
with the observed wavenumbers in FTIR spectra. The kinetic model that better describes the second reaction
of dehydration for FePO4·3H2O is the Fn model as a simple n-order reaction, and the corresponding function
is ×c4(
) = (1-)2.50 and g() = -[1-(1-)-1.50/(1.50)].
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