Iron sulfate, in particular FeSO 4 ·7H 2 O, is derived from titanium dioxide production and the steel pickling process. Regarding TiO 2 manufacturing, the amount of the resultant FeSO 4 ·7H 2 O can be as high as 6 tons per ton of produced TiO 2 , leading to a huge amount of ferrous sulfate heptahydrate, which is considered an environmental and economic concern for the titanium dioxide industry in European countries. The present paper focuses on the thermal treatment of ferrous sulfate (heptahydrate and monohydrate) samples under different conditions. Nonisothermal thermogravimetric (TG) analysis was used to study the behavior of iron sulfate samples at temperatures of up to 1000 • C in Cl 2 + O 2 , O 2 , and N 2 atmospheres. Results showed that the dehydration of iron sulfate heptahydrate in nitrogen started at room temperature and resulted in iron sulfate tetrahydrate (FeSO 4 ·4H 2 O). The ferrous sulfate monohydrate (FeSO 4 ·H 2 O) was formed at temperatures close to 150 • C, while the anhydrous ferrous sulfate (FeSO 4) was obtained when the samples were heated in nitrogen at over 225 • C. The kinetic features of FeSO 4 decomposition into Fe 2 O 3 were revealed under isothermal conditions at temperatures ranging from 500 to 575 • C. The decomposition of iron sulfate was characterized by an apparent activation energy of around 250 kJ/mol, indicating a significant temperature effect on the decomposition process. The obtained powder iron oxide could be directed to the agglomeration unit of iron and the steelmaking process.