Aqueous Oxidation of Iron Monosulfide (FeS) by Molecular Oxygen

ABSTRACT

Aqueous oxidation of iron monosulfide (FeS) by oxygen at initial pH between 2.5 and 5 was investigated in a closed system at different temperatures (25, 35, and 40°C). It was found that the rate of aqueous oxidation of FeS increases when initial [H⁺] and temperature increase. The reaction order with respect to [H⁺] was 0.16 ± 0.02 at 25°C. The activation energy was found to be 23 ± 5 kJ mol^–1 at initial pH 2.5. This value suggests that aqueous oxidation of FeS by oxygen is controlled by a mixed regime of diffusion and surface reaction control. FTIR analysis of the initial and reacted FeS samples has shown that during the aqueous oxidation of FeS by O₂ a sulfur-rich layer is formed on the mineral surface. The experimental results indicate that the protons adsorb on the mineral surface and catalyze Fe²⁺ release into solution (by Couloumbic repulsion) and S(-II) oxidation to higher oxidation states.

KEYWORDS:

• Closed system
• FeS
• oxygen
• pH
• temperature

Acknowledgments

The comments and suggestions of an anonymous reviewer are gratefully acknowledged for their valuable contributions to this manuscript.

Funding

The work was partly funded by the Capacitati Program (Project number 04/2010).

Additional information

Funding

The work was partly funded by the Capacitati Program (Project number 04/2010).