Mechanism of solid-state oxidation of FeSO4 center dot H2O: model of simultaneous reactions

The mechanism of the thermal transformation of FeSO4.H2O in air has been st udied under isothermal conditions at temperatures (150-460)degreesC using m ainly Fe-57 Mossbauer spectroscopy and X-ray powder diffraction (XRD). Two trends are typical for the thermal behaviour of FeSO4.H2O in air, a tendenc y toward oxidation and dehydration. We suggested a new transformation model consisting of two ways of oxidation, direct one and indirect one. Fe(OH)SO 4 was identified as a product of the direct way, Fe-2(SO4)(3) and superpara magnetic: nanoparticles of gamma -Fe2O3 as products of the indirect way. Th e suggested model of simultaneous reactions explains the unusual non-monoto nous dependence of the oxidation level of the thermally treated samples on temperature.