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

Jagannath Biswakarma; Kyounglim Kang; Susan C. Borowski; Walter D.C. Schenkeveld; Stephan M. Kraemer; Janet G. Hering; Stephan J. Hug

doi:10.1021/acs.est.8b03910

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

Jagannath Biswakarma, Kyounglim Kang, Susan C. Borowski, Walter D.C. Schenkeveld, Stephan M. Kraemer, Janet G. Hering, Stephan J. Hug^*

^*Corresponding author for this work

Research output: Contribution to journal › Article (Academic Journal) › peer-review

32 Citations (Scopus)

Abstract

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 ⁵⁷ Fe 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 ⁵⁷ Fe remained in solution, or quickly reappeared in solution when EDTA was added after ⁵⁷ Fe(II), suggesting that catalyzed dissolution occurred at or near the site of ⁵⁷ Fe 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.

Original language	English
Pages (from-to)	88-97
Number of pages	10
Journal	Environmental Science and Technology
Volume	53
Issue number	1
DOIs	https://doi.org/10.1021/acs.est.8b03910
Publication status	Published - 2 Jan 2019

Bibliographical note

Funding Information:
We thank Thomas Ruettimann (Eawag) for ICP−MS analyses and for technical assistance. We also thank Numa Pfenninger (Eawag) for BET and XRD measurements and Dr. Ralf Kaegi (Eawag) for SEM images. This project was financially supported by the Swiss National Science Foundation, project number 200021L_150150 “Synergistic effects of redox processes and ligand-controlled dissolution of iron(hydr)oxide phases” Mathematics, Natural Sciences, and Engineering (Division II). S.K., W.S., and K.K. were supported by the Austrian Science Fund (FWF, Grant No.: I 1528-N19).

Publisher Copyright:
© 2018 American Chemical Society.

Access to Document

10.1021/acs.est.8b03910

Handle.net

Persistent link

Cite this

@article{8933cbb83ec2444cb58637bbf368947d,

title = "Fe(II)-Catalyzed Ligand-Controlled Dissolution of Iron(hydr)oxides",

abstract = " 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 57 Fe 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 57 Fe remained in solution, or quickly reappeared in solution when EDTA was added after 57 Fe(II), suggesting that catalyzed dissolution occurred at or near the site of 57 Fe 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. ",

author = "Jagannath Biswakarma and Kyounglim Kang and Borowski, {Susan C.} and Schenkeveld, {Walter D.C.} and Kraemer, {Stephan M.} and Hering, {Janet G.} and Hug, {Stephan J.}",

note = "Funding Information: We thank Thomas Ruettimann (Eawag) for ICP−MS analyses and for technical assistance. We also thank Numa Pfenninger (Eawag) for BET and XRD measurements and Dr. Ralf Kaegi (Eawag) for SEM images. This project was financially supported by the Swiss National Science Foundation, project number 200021L_150150 “Synergistic effects of redox processes and ligand-controlled dissolution of iron(hydr)oxide phases” Mathematics, Natural Sciences, and Engineering (Division II). S.K., W.S., and K.K. were supported by the Austrian Science Fund (FWF, Grant No.: I 1528-N19). Publisher Copyright: {\textcopyright} 2018 American Chemical Society.",

year = "2019",

month = jan,

day = "2",

doi = "10.1021/acs.est.8b03910",

language = "English",

volume = "53",

pages = "88--97",

journal = "Environmental Science and Technology",

issn = "0013-936X",

publisher = "American Chemical Society",

number = "1",

}

TY - JOUR

T1 - Fe(II)-Catalyzed Ligand-Controlled Dissolution of Iron(hydr)oxides

AU - Biswakarma, Jagannath

AU - Kang, Kyounglim

AU - Borowski, Susan C.

AU - Schenkeveld, Walter D.C.

AU - Kraemer, Stephan M.

AU - Hering, Janet G.

AU - Hug, Stephan J.

N1 - Funding Information: We thank Thomas Ruettimann (Eawag) for ICP−MS analyses and for technical assistance. We also thank Numa Pfenninger (Eawag) for BET and XRD measurements and Dr. Ralf Kaegi (Eawag) for SEM images. This project was financially supported by the Swiss National Science Foundation, project number 200021L_150150 “Synergistic effects of redox processes and ligand-controlled dissolution of iron(hydr)oxide phases” Mathematics, Natural Sciences, and Engineering (Division II). S.K., W.S., and K.K. were supported by the Austrian Science Fund (FWF, Grant No.: I 1528-N19). Publisher Copyright: © 2018 American Chemical Society.

PY - 2019/1/2

Y1 - 2019/1/2

N2 - 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 57 Fe 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 57 Fe remained in solution, or quickly reappeared in solution when EDTA was added after 57 Fe(II), suggesting that catalyzed dissolution occurred at or near the site of 57 Fe 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.

AB - 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 57 Fe 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 57 Fe remained in solution, or quickly reappeared in solution when EDTA was added after 57 Fe(II), suggesting that catalyzed dissolution occurred at or near the site of 57 Fe 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.

UR - http://www.scopus.com/inward/record.url?scp=85059414889&partnerID=8YFLogxK

U2 - 10.1021/acs.est.8b03910

DO - 10.1021/acs.est.8b03910

M3 - Article (Academic Journal)

C2 - 30571098

AN - SCOPUS:85059414889

SN - 0013-936X

VL - 53

SP - 88

EP - 97

JO - Environmental Science and Technology

JF - Environmental Science and Technology

IS - 1

ER -

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

Abstract

Bibliographical note

Access to Document

Handle.net

Other files and links

Fingerprint

Cite this