Lloyd, Thomas (1999) Dissolution of Fe(III)- and Mn(III,IV)- (hydr)oxides by deferrioxamine B. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechETD:etd-02082008-163932
NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.
Microbially produced siderophores are thought to have evolved to increase the availability of iron in oxic aqueous systems. Historically, it has been assumed that siderophores interact with iron found in Fe(III)-(hydr)oxides, removing iron from the solid to form ferrated aqueous species of the siderophore available for uptake by the microorganism. However, this proposed interaction of siderophore with the solid phase has not been examined in detail.
The work presented in this thesis examines the interaction of a model trihydroxamic acid siderophore (deferrioxamine B) with synthetic Fe(III)-, Mn(III), Mn(IV)- (hydr)oxide particles. The experiments were designed to characterize the mineral dissolution process mediated by deferrioxamine B (DFA). DFA was found to dissolve all the solid particles used in the study. The Fe(III)- (hydr)oxides dissolved exclusively by a nonreductive mechanism. The dissolution is a surface-mediated process. Dissolution of manganite was found to be analogous to the Fe(III)-(hydr)oxide dissolution process, while the dissolution of pyrolusite was found to follow a complicated mechanism that involves reductive processes. The interactions between DFA and the solid surface are examined experimentally and theoretically.
Under the conditions in which (i) the concentration of DFA in solution remains essentially constant over the course of the reaction, i.e., the concentration of the ferrated form of DFA (FA) is much less than [DFA][...] over the whole time of the reaction, and (ii) the concentration of available surface sites remains constant, the dissolution rate can be modeled as a pseudo-zero [...] order reaction, where
R = k'.
Under the same conditions and where the concentration of adsorbed DFA is measured, the dissolution rate can be modeled as a pseudo-first order process, where
R = k [[...]Fe — DFA],
where [[...]Fe — DFA] is defined as the concentration of adsorbed DFA. Conditions (i) and (ii) imply that a necessary condition for observation of a pseudo-zero [...] order process is that [[...]Fe — DFA] remains constant over the course of the reaction. Where these conditions fail, the dissolution process becomes more complicated, and the experiments presented here do not address these cases in detail.
|Item Type:||Thesis (Dissertation (Ph.D.))|
|Degree Grantor:||California Institute of Technology|
|Division:||Engineering and Applied Science|
|Major Option:||Environmental Science and Engineering|
|Thesis Availability:||Restricted to Caltech community only|
|Defense Date:||1 January 1999|
|Default Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Imported from ETD-db|
|Deposited On:||20 Feb 2008|
|Last Modified:||26 Dec 2012 02:30|
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