FeSO4 is a waste obtained in the production of TiO2 and also in steel etching in block metallurgy. The thermochemical decomposition of different FeSO4 - FeS2 - BaO2 mixtures was studied by means of a derivatograph, X-ray diffraction, Mossbauer spectroscopy, EMF and other methods in order to understand the chemical transformations, new solid phases and kinetic limitations in the temperature range 292 - 1292 K. It was shown that there is a multistep process in which BaSO4, FeS, BaFeO3 and BaFe2O4 can be formed as intermediates. Depending on the initial ratio of the components, the atmosphere and the temperature range, different phase compositions of the final solid product can be obtained. At the present stage of the investigations, the possibility of obtaining pure barium ferrite as a product is not confirmed.
