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Abstract: The thermal decomposition of tribochemically activated Al2(SO4)3xH2O was studied by TG, DTA and EMF methods. For some of the intermediate solids, X-ray diffraction and IR-spectroscopy were applied to learn more about the reaction mechanism. Thermal and EMF studies confirmed that, even after mechanical activation of Al2(SO4)3xH2O, Al2O(SO4)2 is formed as an intermediate. Isothermal kinetic experiments demonstrated that the thermochemical sulphurization of inactivated Al2(SO4)3xH2O has an activation energy of 102.2 kJmol−1 in the temperature range 850–890 K. The activation energy for activated Al2(SO4)3xH2O in the range 850–890 K is 55.0 kJmol−1. The time of thermal decomposition is almost halved when Al2(SO4)3xH2O is activated mechanically. The results permit conclusions concerning the efficiency of the tribochemical activation of Al2(SO4)3xH2O and the chemical and kinetic mechanisms of the desulphurization process.

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, Mössbauer 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, BaFeC3 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.

The effect of P2O5 on the thermal decomposition of phosphogypsum to phospholime and sulphur dioxide has been studied.

Thermochemical decomposition of phosphogypsum was studied in the temperature range 1000-1100° C.Carrier gas contains 4%CO, 5–20% CO2and Ar. The kinetics study of decomposition enable to calculate activation energy derived from the Arrhenius equation.The results are compared with our earlier work in CO-Ar atmosphere.