Fe(II)-Catalyzed Ligand-Controlled Dissolution of Iron(hydr)oxides

Autor(en)

Jagannath Biswakarma, Kyounglim Kang, Susan Borowski, Walter Schenkeveld, Stephan Krämer, Janet Hering, Stephan Hug

Abstrakt

Dissolution of iron(III)phases is a key process in soils, surface waters, and the ocean. Previous studies found that traces of Fe(II) can greatly increase ligand controlled dissolution rates at acidic pH, but the extent that this also occurs at circumneutral pH and what mechanisms are involved are not known. We addressed these questions with infrared spectroscopy and 57Fe isotope exchange experiments with lepidocrocite (Lp) and 50 μM ethylenediaminetetraacetate (EDTA) at pH 6 and 7. Addition of 0.2–10 μM Fe(II) led to an acceleration of the dissolution rates by factors of 7–31. Similar effects were observed after irradiation with 365 nm UV light. The catalytic effect persisted under anoxic conditions, but decreased as soon as air or phenanthroline was introduced. Isotope exchange experiments showed that added 57Fe remained in solution, or quickly reappeared in solution when EDTA was added after 57Fe(II), suggesting that catalyzed dissolution occurred at or near the site of 57Fe incorporation at the mineral surface. Infrared spectra indicated no change in the bulk, but changes in the spectra of adsorbed EDTA after addition of Fe(II) were observed. A kinetic model shows that the catalytic effect can be explained by electron transfer to surface Fe(III) sites and rapid detachment of Fe(III)EDTA due to the weaker bonds to reduced sites. We conclude that the catalytic effect of Fe(II) on dissolution of Fe(III)(hydr)oxides is likely important under circumneutral anoxic conditions and in sunlit environments.

Organisation(en)

Department für Umweltgeowissenschaften

Externe Organisation(en)

Eidgenössische Technische Hochschule Zürich

Journal

Environmental Science & Technology

Band

53

Seiten

88-97

Anzahl der Seiten

10

ISSN

0013-936X

DOI

https://doi.org/10.1021/acs.est.8b03910

Publikationsdatum

01-2019

Peer-reviewed

Ja

ÖFOS 2012

104014 Oberflächenchemie, 105906 Umweltgeowissenschaften

Schlagwörter

ASJC Scopus Sachgebiete

Allgemeine Chemie, Environmental Chemistry

Link zum Portal

https://ucrisportal.univie.ac.at/de/publications/8ea0c7db-66d4-4d82-83e6-c734217689ba