Abstract:
The solubility data of ferrous sulfate hydrates in dilute H
2SO
4 solutions (mass fraction 1% and 3%) at 293.15~363.15 K were determined by static equilibrium method. X-Ray diffraction and thermogravimetric analysis were employed to identify the phases and formations of the crystals. It was showed that in the 1% H
2SO
4 solution, the crystals showed three forms of ferrous sulfate heptahydrate, ferrous sulfate tetrahydrate and ferrous sulfate monohydrate. While in the 3% H
2SO
4 solution only two distinct crystal phases were detected, i.e., ferrous sulfate heptahydrate and monohydrate. The solubility of ferrous sulfate was highly dependent on the temperature and acidity. The solubility firstly increased with the increase of temperature, while decreased when the temperature was higher than the transition temperature. The solubility decreased with the increase of the acidity at the same temperature. The results obtained in this work can offer fundamental thermodynamic data for the wet crystal phase transformation of ferrous sulfate.