Oxidative dissolution of pyrite in acidic media
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The pyrite oxidative dissolution in air-saturated (AS), H2O2, and Fe3+ solutions at pH 2.5 and 25 °C was investigated by electrochemical and aqueous batch experiments. The corrosion current density (i corr) increases from AS solution to Fe3+ and H2O2 solutions. For the same oxidant, i corr increases when the concentration of the oxidant increases. Similar variation was observed for the corrosion potential (E corr). Electrochemical impedance spectroscopy measurements have indicated that in AS and H2O2 solutions, the charge transfer is the rate determining step of pyrite oxidative dissolution. In the presence of Fe (aq) 3+ , both the charge transfer process and mass transfer caused by the diffusion of oxidant or reaction products across the interface of electrode control the mineral oxidative dissolution. The corrosion current densities of oxidative dissolution measured by electrochemical methods are higher than those estimated from dissolution rates determined by aqueous bath experiments. The observed differences suggest that the mechanism of polarized electrode oxidation is different by the mechanism of pyrite oxidation under open circuit conditions.
KeywordsPyrite Oxidation Mechanism Electrochemical impedance spectroscopy
This work was partially supported by the strategic grant POSDRU/CPP107/DMI1.5/S/78421, Project ID 78421 (2010), co-financed by the European Social Fund-Investing in People, within the Sectorial Operational Programme Human Resources Development 2007–2013.
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