On the rest potential of pyrite electrode in oxygen-free solutions of iron (II) sulfate
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Polish Academy of Sciences, Institute of Catalysis and Surface Chemistry
Jagiellonian University
Publication date: 2002-01-01
Physicochem. Probl. Miner. Process. 2002;36(1):77–88
The exchange current density (ECD) for the reaction: Fe1+ yS2 = Fe1+ y−xS2 + xFe2+ + 2xe was estimated measuring the impedance of pyrite electrodes in the solutions of iron (II) sulfate. For five different pyrite electrodes, 0.5 mol dm-3 FeSO4 solution and potentials close to the potential of the reaction FeS2 = Fe2+ + 2S0 + 2e the ECD was found to be between 8 and 15 μA cm2. Low value of the ECD causes that the potential of pyrite electrode in solutions of iron (II) sulfate does not attain the equilibrium value (i.e. the value within the range of pyrite thermodynamic stability) except the most concentrated and very well deoxidized solutions. For the concentrations of FeSO4 solution lower than 0.5 mol dm-3 pyrite electrode shows the rest potential outside the limits of thermodynamic stability, which means that the measured potential is a mixed (corrosion), not equilibrium potential.