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The mechanisms of ligand adsorption and iron oxide dissolution in the presence of biogenic surfactants

English title The mechanisms of ligand adsorption and iron oxide dissolution in the presence of biogenic surfactants
Applicant Kretzschmar Ruben
Number 112280
Funding scheme Project funding (Div. I-III)
Research institution Institut für Biogeochemie und Schadstoffdynamik ETH Zürich
Institution of higher education ETH Zurich - ETHZ
Main discipline Pedology
Start/End 01.04.2006 - 31.12.2006
Approved amount 41'858.00
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Keywords (8)

surfactants; extracellular biogenic compounds; biological iron acquisition; siderophores; ligand controlled dissolution; dissolution; iron oxides; surface chemistry

Lay Summary (English)

Lead
Lay summary
Many microorganisms and plants produce and release bio-surfactants, for example, in the soil directly surrounding active plant roots (called the rhizosphere). Surfactants are organic compounds with hydrophilic head groups and hydrophobic tails. They generally have a high affinity for mineral surfaces due to electrostatic and hydrophobic interactions.Adsorption of surfactants onto mineral surfaces has pronounced effects on the physico-chemical properties of the mineral-water interface (e.g., surface charge, hydrophobicity). Therefore, we hypothesized that presence of surfactants may have strong effects on a variety of reactions between microorganisms or plant roots exudates and mineral surfaces occurring in soils and other natural environments. One such reaction is the acquisition of the essential nutrient iron by microorganisms or plants through the release of siderophores. Siderophores are organic compounds that strongly bind iron and that promote dissolution of iron bearing minerals by a so called ligand-controlled dissolution mechanism.

The specific objective of this work was to study the influence of surfactants on the ligand-controlled dissolution of goethite (α-FeOOH), one of the most common iron oxide minerals in soils and sediments. Two different siderophores and a synthetic ligand (EDTA) were chosen as the complexing ligands. Sodium dodecyl sulfate (synthetic) and rhamnolipids (biogenic) were used as surfactants. Our results revealed that low amounts of adsorbed surfactants significantly increase the ligand-controlled dissolution rates of goethite. The dissolution rates were not proportional to the amount of adsorbed ligands, as stipulated by the rate law of ligand-controlled dissolution. We hypothesized that the enhancement of dissolution rates in the presence of surfactants is related to changing surface speciation of the adsorbed ligand and changes of the surface protonation by proton co-adsorption with the surfactants. Our results suggest that bio-surfactants may play an important role in the iron acquisition by bacteria and roots of certain plant species which release siderophores under iron-limiting conditions.
Direct link to Lay Summary Last update: 21.02.2013

Responsible applicant and co-applicants

Employees

Publications

Publication
Adsorption of hydroxamate siderophores and EDTA on goethite in the presence of the surfactant sodium dodecyl sulfate
Carrasco N, Kretzschmar R, Xu JD, Kraemer SM (2009), Adsorption of hydroxamate siderophores and EDTA on goethite in the presence of the surfactant sodium dodecyl sulfate, in GEOCHEMICAL TRANSACTIONS, 10, 1186-1467.
Effects of anionic surfactants on ligand-promoted dissolution of iron and aluminum hydroxides
Carrasco N, Kretzschmar R, Pesch ML, Kraemer SM (2008), Effects of anionic surfactants on ligand-promoted dissolution of iron and aluminum hydroxides, in JOURNAL OF COLLOID AND INTERFACE SCIENCE, 321(2), 279-287.
Low concentrations of surfactants enhance siderophore-promoted dissolution of goethite
Carrasco N, Kretzschmar R, Pesch ML, Kraemer SM (2007), Low concentrations of surfactants enhance siderophore-promoted dissolution of goethite, in ENVIRONMENTAL SCIENCE & TECHNOLOGY, 41(10), 3633-3638.

Associated projects

Number Title Start Funding scheme
66910 The influence of biogenic surfactants on mineral weathering 01.12.2002 Project funding (Div. I-III)

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