Kinetics and Mechanism of the Reaction of Hydrogen Sulfide with Lepidocrocite
The initial reaction between hydrogen sulfide and the surface of lepidocrocite was studied in the pH range between 4 and 8.6 by monitoring the change of the emf of a pH2S sensor. The rate of H2S oxidation is pseudo first order with respect to H2S and shows a strong pH dependence with a maximum at pH...
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| Autores principales: | , , , |
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| Formato: | JOUR |
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| Acceso en línea: | http://hdl.handle.net/20.500.12110/paper_0013936X_v26_n12_p2408_Stefan |
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| Sumario: | The initial reaction between hydrogen sulfide and the surface of lepidocrocite was studied in the pH range between 4 and 8.6 by monitoring the change of the emf of a pH2S sensor. The rate of H2S oxidation is pseudo first order with respect to H2S and shows a strong pH dependence with a maximum at pH 7. Two rate laws were derived: R(5<pH<6) = ka[H+]-2[H2S]tot,A and R(7<PH<8.6) = Kb[H+]1[H2S]totA with ka = 1.5 × 10-13 M2 min-1 and kb = 2 X 106 M-1 min-1. The pH maximum of the reaction rate can be explained by using a surface speciation model suggested for the reductive dissolution of hematite by H2S (1): The oxidation rate of H2S is proportional to the concentration of inner-sphere surface complexes of HS- formed with either the neutral ferric oxide surface sites (>FeOH) or the protonated ferric oxide surface sites (>FeOH2+). The amount of protons consumed per mole of H2Stot suggests that polysulfides and elemental sulfur are the initial products formed during the experiments. © 1992, American Chemical Society. All rights reserved. |
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