Dissolution mechanisms of goethite in the presence of siderophores and organic acids

Roles of Siderophores, Oxalate, and Ascorbate in Mobilization of Iron from Hematite by the Aerobic Bacterium Pseudomonas mendocina

“…Although the oxalate alone did not have an appreciable effect on the growth kinetics and final culture density, a clear advantage over DFO-B alone was observed when a small amount of DFO-B was also present. This effect was not seen when oxalate was added simultaneously with DFO-B and the bacteria (data not shown), indicating that pretreatment is important to allow time for the initial labilization of surface iron from hematite by the adsorbed oxalate, as previously shown by Reichard et al in abiotic studies (41).…”

“…The model is described simply here as follows for amorphous Fe(OH) 3 and has been described in detail by Kraemer (26): Fe(OH) 3 (39), suggests that [FeL] could in principle easily be micromolar or higher and could support vigorous bacterial growth. However, the trishydroxamate siderophores that have been studied most to date adsorb only weakly to Fe(III) (hydr)oxide minerals, likely due to steric constraints, although charge repulsion may also play a role for positively charged siderophores, such as desferrioxamine B (DFO-B) (6,26,41,42). Therefore, it has been proposed that siderophores act primarily in conjunction with other molecules, such as simple plant-derived carboxylic acids or reductants, which interact more strongly with mineral surfaces and release Fe directly through ligand-promoted and/or reductive mechanisms (52).…”

“…This proposed "synergistic effect," in which the combined effect of various elements is greater than the sum of the individual effects, suggests that an interaction of biogenic molecules may overcome kinetic and thermodynamic barriers to the release of Fe from minerals in the presence of siderophores. The role of the siderophore in such a synergistic system is not a direct role in surface processes; rather, the siderophore maintains a low concentration of aqueous Fe in equilibrium with the mineral (an Fe sink), thus driving the reaction toward more dissolution (26,41). Only a low concentration of a siderophore relative to the concentra-tions of surface-reacting organic species is required to promote efficient dissolution (26).…”

Analysis of Cleaning Process for Several Kinds of Soil by Probability Density Functional Method

“…As recent studies on the cleaning of metalbased soils by dissolution, Zhang 35 and Debnath 36 reported the dissolution of iron-based soil using ascorbic acid as a reducing agent, AI-Mayouf reported the dissolution of magnetite using ethylenediamine disuccinic acid as a chelating agent 37 , and Reichard studied the dissolution of goethite using organic acids and siderphores 38 .…”

Mechanisms of goethite dissolution in the presence of desferrioxamine B and Suwannee River fulvic acid at pH 6.5

“…Furthermore, at hydroxamate siderophore concentrations typical of 53 soils (i.e. 10 -7 -10 -8 M; Powell et al, 1980), goethite solubility increases over a wide pH 54 range (Kraemer, 2004), where the dissolution of goethite at pH > 4 is described as ligand-55 controlled (Holmén and Casey, 1996;Reichard et al, 2007a). 56…”