Mechanism of solid-state oxidation of FeSO4·H2O: model of simultaneous reactions
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The mechanism of the thermal transformation of FeSO4·H2O in air has been studied under isothermal conditions at temperatures (150–460)°C using mainly57Fe Mössbauer spectroscopy and X-ray powder diffraction (XRD). Two trends are typical for the thermal behaviour of FeSO4·H2O in air, a tendency toward oxidation and dehydration. We suggested a new transformation model consisting of two ways of oxidation, direct one and indirect one. Fe(OH)SO4 was identified as a product of the direct way, Fe2(SO4)3 and superparamagnetic nanoparticles ofγ-Fe2O3 as products of the indirect way. The suggested model of simultaneous reactions explains the unusual non-monotonous dependence of the oxidation level of the thermally treated samples on temperature.
KeywordsFeSO4 Maghemite Oxidation Level Thermal Transformation Simultaneous Reaction
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