The reductive dissolution of hematite by H2S was investigated under conditions of constant partial pressure of H2S (10-4 to 10-2 atm), pH = 3-7 and 25°C, and under conditions where the solubility product of iron sulfide is not exceeded. The reaction proceeds by an initial (relatively fast) formation of ≡FeS- and ≡FeSH surface complexes; subsequently, electron transfer and detachment of Fe(II) from the oxide surface occur. The rate law for the dissolution can be interpreted by assuming a surface-controlled reaction depending on the surface concentration of the surface complexes ≡FeS- and ≡FeSH: Rt = ke{≡FeS-} + ke′{≡FeSH} where {≡FeS-} and {≡FeSH} are surface concentrations in mol·m-2. The experimental data are compatible with the constants ke = 30 h-1 and ke′ = 400 h-1 and surface complex formation constants for ≡FeS- (≡FeOH + H2S(g) ⇄ ≡FeS- + H+ + H2O) and ≡FeSH (≡FeOH + H2S(g) ⇄ ≡FeSH + H2O) of log Ks = -2.70 and 2.82, respectively. Preliminary experiments with lepidocrocite and goethite give results on the reaction rates that show the same kind of dependence on solution variables as those with α-Fe2O3 and are compatible with the mechanism proposed here. © 1992 American Chemical Society.
Documento: | Artículo |
Título: | Reductive dissolution of iron(III) (hydr)oxides by hydrogen sulfide |
Autor: | Dos Santos Afonso, M.; Stumm, W. |
Filiación: | Swiss Federal Institute for Water Resources and Water Pollution Control (EAWAG), Swiss Federal Institute of Technology (ETH), Duebendorf, Switzerland Depto de Química Inorgánica, Analítica y Química Física, Ciudad Universitaria Pabellón II, 1428 Buenos Aires, Argentina |
Idioma: | Inglés |
Año: | 1992 |
Volumen: | 8 |
Número: | 6 |
Página de inicio: | 1671 |
Página de fin: | 1675 |
Título revista: | Langmuir |
ISSN: | 07437463 |
Registro: | https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_07437463_v8_n6_p1671_DosSantosAfonso |