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Temperature dependence of goethite dissolution promoted by trihydroxamate siderophores |
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| Authors: | Claudio CocozzaCalvin CG Tsao Sing-Foong CheahStephan M Kraemer Kenneth N RaymondTeodoro M Miano Garrison Sposito |
| Institution: | 1 Dipartimento di Biologia e Chimica Agro-Forestale e Ambientale, Universitá degli Studi di Bari, 70126 Bari, Italy 2 Division of Ecosystem Sciences, University of California, Berkeley, CA 94720-3110, USA 3 Institute of Terrestrial Ecology, ETH-Zürich, CH-8952, Schlieren, Switzerland 4 Department of Chemistry, University of California, Berkeley, CA 94720-1460, USA |
| Abstract: | This article reports an investigation of the temperature dependence of goethite dissolution kinetics in the presence of desferrioxamine B (DFO-B), a trihydroxamate siderophore, and its acetyl derivative, desferrioxamine D1 (DFO-D1). At 25 and 40°C, DFO-D1 dissolved goethite at twice the rate of DFO-B, whereas at 55°C, the behavior of the two ligands was almost the same. Increasing the temperature from 25 to 55°C caused little or no significant change in DFO-B or DFO-D1 adsorption by goethite. A pseudo-first-order rate coefficient for dissolution, calculated as the ratio of the mass-normalized dissolution rate coefficient to the surface excess of siderophore, was approximately the same at 25 and 40°C for both siderophores. At 55°C, however, this rate coefficient for DFO-D1 was about half that for DFO-B. Analysis of the temperature dependence of the mass-normalized dissolution rate coefficient via the Arrhenius equation led to an apparent activation energy that was larger for DFO-B than for DFO-D1, but much smaller than that reported for the proton-promoted dissolution of goethite. A compensation law was found to relate the pre-exponential factor to the apparent activation energy in the Arrhenius equation, in agreement with what has been noted for the proton-promoted dissolution of oxide minerals and for the complexation of Fe3+ by DFO-B and simple hydroxamate ligands in aqueous solution. Analysis of these results suggested that the siderophores adsorb on goethite with a only single hydroxamate group in bidentate ligation with an Fe(III) center. |
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