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

Abstract

Naturally occurring goethites often show Al for Fe substitution approaching 33 mol% Al. This substitution has potential to influence the rate of goethite dissolution and therefore the supply of bioavailable Fe. Siderophores such as ferrichrome and enterobactin have considerable potential to dissolve Fe from Fe 3? rich minerals, including Al-substituted goethites. Here, we show that Al substitution in synthetic goethites (0.021 C x C 0.098) gives rise to a significant increase in both ferrichrome-and enterobactin-mediated dissolution rates. In the presence of ferrichrome, Al-goethite (x = 0.033) yields a dissolution rate of 19.0 9 10 -3 lmol m -2 h -1 , nearly twice that of pure goethite, whereas dissolution of the most highly substituted Al-goethite (x = 0.098) is 36.9 9 10 -3 lmol m -2 h -1, more than threefold greater than the pure mineral. Similarly, in the presence of enterobactin, the dissolution rate of Al-goethite increases with increasing Al substitution. Ferrichrome is a less effective ligand than enterobactin in its dissolution of both pure goethite and the range of Al-goethites, an observation we ascribe to the lower affinity of the hydroxamate functional groups of ferrichrome for both Fe 3? and Al 3? . Despite greater affinity of both ferrichrome and enterobactin for Fe 3? over Al 3? , we observe a broadly congruent dissolution of all our Al-goethites.

In vitro assessment of cobalt oxide particle dissolution in simulated lung fluids for identification of new decorporating agents

“…Siderophore-promoted dissolution has also been described for iron oxides. Dubbin et al, described an increase in iron release from synthetic goethite in the presence of ferrichrome and enterobactin at pH 6.5 (Dubbin and Bullough, 2017). Desferrioxamine B (DFOB) has been shown to increase Fe release from Cr(III)-Fe(III)-(oxy)hydroxides in an HEPES buffer at pH 7, and oxalate acted synergistically with DFOB to increase the Fe release (Saad et al, 2017).…”

Iron and manganese mobilisation due to dam height increase for a tropical reservoir in South East Asia

“…This reaction depends on the available surface area of goethite for reduction as the surface area can become passivated, e.g. due to the accumulation of aluminium (Dubbin and Bullough 2017).…”

Contrasting effects of siderophores pyoverdine and desferrioxamine B on the mobility of iron, aluminum, and copper in Cu-contaminated soils

“…The process is hypothesized to be the same for DFOB and Pvd and, in accordance with the hypothesis formulated above, a first explanation is that Cu 2+ ions adsorbed onto the surface of Fe-bearing phases in preference to the Al-bearing phases in soil L. According to this hypothesis, the accumulation of Cu 2+ ions promoted the adsorption of siderophores onto the surface of Fe-bearing phases (notably Fe-oxides) thereby increasing the rate of Fe release. Another possible explanation based on the study by Dubbin and Bullough (2017) is that the accumulation of Cu 2+ ions at the surface of Al-bearing phases blocked the reactive sites of Al dissolution thereby reducing the rate of Al mobilization by DFOB and Pvd.…”