Temperature dependence of goethite dissolution promoted by trihydroxamate siderophores

Abstract

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 Fe 3ϩ 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.

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

“…Although siderophores are essential for Fe uptake by many aerobic bacteria, they are inefficient at releasing Fe from the surfaces of the mineral species that are the most common terrestrial sources of Fe (6,9,22,25,27). They also inevitably diffuse away from the source of production and into the greater geologic matrix.…”

Dissolution of Al-Substituted Goethite in the Presence of Ferrichrome and Enterobactin at pH 6.5

“…The initial dissolution rates of pure goethite by ferrichrome and enterobactin are 9.91 9 10 -3 and 35.9 9 10 -3 lmol m -2 h -1 , respectively. This compares with dissolution rates of 3.86 9 10 -3 lmol m -2 h -1 (Cocozza et al 2002) and ; pH 6.5; 25°C…”

“…The surface excess for each siderophore was then derived by dividing the enterobactin or ferrichrome lost from solution by the goethite surface area. On the basis of previous studies that show there is an optimal reaction period during which ligand adsorption is achieved, but where dissolution is minimal (Cocozza et al 2002;Simanova et al 2010), we choose 30 min reaction time to determine maximum siderophore surface excess.…”

“…When the dissolution rates are normalised for siderophore surface excess through a calculation of the pseudo-first-order rate coefficient, we observe an increase in dissolution kinetics in line with Al substitution. The pseudo-first-order rate coefficient is commonly used to characterise ligand-promoted dissolution kinetics far from equilibrium (Cocozza et al 2002) and is obtained as a ratio by dividing the surface normalised initial dissolution rate by the surface excess of the ligand promoting the dissolution. Steady-state Al release rates for each dissolution experiment are given in Table 3.…”

Effect of desferrioxamine B and Suwannee River fulvic acid on Fe(III) release and Cr(III) desorption from goethite

“…Filtrate DFOB was quantified by the chelometric method, in which concentrations of the Fe(III)-DFOB complex are measured spectrophotometrically by absorption at 467 nm (Cocozza et al, 2002;Cheah et al, 2003). Briefly, 2.5 mL portions of filtrates and standards, the latter containing predetermined quantities of DFOB to construct the calibration curve, were acidified to pH 1.5 to 1.7 with 8 µL 70% HClO 4 (BDH ARISTAR).…”