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Iron(III) precipitates formed by iron(II) oxidation in natural waters: Structure, reactivity and impact on arsenic

English title Iron(III) precipitates formed by iron(II) oxidation in natural waters: Structure, reactivity and impact on arsenic
Applicant Voegelin Andreas
Number 132123
Funding scheme Project funding
Research institution Swiss Federal Institute of Aquatic Science and Technology (EAWAG)
Institution of higher education Swiss Federal Institute of Aquatic Science and Technology - EAWAG
Main discipline Other disciplines of Environmental Sciences
Start/End 01.02.2011 - 31.03.2014
Approved amount 198'448.00
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All Disciplines (4)

Discipline
Other disciplines of Environmental Sciences
Geochemistry
Hydrology, Limnology, Glaciology
Pedology

Keywords (12)

iron; arsenic; phosphate; colloids; nanoparticles; oxidation; precipitation; adsorption; coagulation; structure; X-ray absorption spectroscopy; electron microscopy

Lay Summary (English)

Lead
Lay summary
The oxidation of ferrous (Fe(II)) to ferric iron (Fe(III)) in waters containing phosphate, silicate, calcium (Ca) and trace elements results in short-range-ordered (SRO) Fe(III)-precipitates that control the cycling of major and trace elements at anoxic-oxic boundaries in natural and engineered systems. These precipitates largely vary in composition and degree of Fe(III) polymerization. Their structural diversity and resulting differences in colloidal and chemical behavior however are still poorly understood. The proposed project takes advantage of state-of-the-art synchrotron X-ray absorption spectroscopy (XAS) and analytical electron microscopy (AEM) for the study of SRO Fe(III)-precipitates formed under widely varying chemical conditions. It thereby aims at achieving a new level of understanding regarding the formation, structure and stability of SRO Fe(III)-precipitates and their role in the biogeochemical cycling of major and trace elements. Such mechanistic knowledge is increasingly important for the quantitative description of nutrient and contaminant behaviour in aquatic systems and improved water resource use and water treatment. Specifically, the proposed research will focus on the following four research questions:1) How do the kinetics of Fe oxidation, precipitation, and aggregation/coagulation affect the types, structure and nanometer- to micrometer-scale spatial arrangement of SRO Fe(III)-precipitates?2) How does the composition, structure, and morphology of Fe(III)-Ca-phosphates and -arsenates formed by Fe(II) oxidation in presence of phosphate or/and arsenate vary as a function of solution chemistry?3) How does the composition, structure and morphology of different SRO Fe(III)-precipitates change during aging and how do these changes affect their solubility?4) How does Fe oxidation, precipitation and aging affect the co-oxidation and co-transformation of As and what are the implications for As removal in water treatment and for biogeochemical As cycling?To address these questions, Fe(II) (and As(III)) oxidation experiments will be designed that capture the complex interplay of key parameters (concentrations of Fe(II), phosphate, silicate, Ca, As (III) or As(V); solution pH; O2 partial pressure; ionic strength) while being controlled enough to allow for a quantitative description and modeling of the observed processes. XAS will provide molecular-level insight into precipitate structure from the perspective of local element coordination, and AEM into particle composition, structure, and morphology from the nanometer- to the micrometer scale.
Direct link to Lay Summary Last update: 21.02.2013

Responsible applicant and co-applicants

Employees

Publications

Publication
Dynamic Fe-precipitate formation induced by Fe(II) oxidation in aerated phosphate-containing water
Voegelin Andreas, Senn Anna-Caterina, Kaegi Ralf, Hug Stephan J., Mangold S. (2013), Dynamic Fe-precipitate formation induced by Fe(II) oxidation in aerated phosphate-containing water, in Geochimica et Cosmochimica Acta, 117, 216-231.

Collaboration

Group / person Country
Types of collaboration
Synchrotron ANKA, Karlsruher Institut für Technologie Germany (Europe)
- Publication
- Research Infrastructure

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
Goldschmidt Conference 2014 Talk given at a conference Structure, composition and arsenate uptake of Fe oxidation products 08.06.2014 Sacramento, United States of America Voegelin Andreas; Hug Stephan; Kägi Ralf; Senn Anna-Caterina;
Goldschmidt Conference 2014 Talk given at a conference Natural nanoparticles: Formation and impact on trace elements 08.06.2014 Sacramento, United States of America Voegelin Andreas;
International Seminar "Dynamic Processes in Capillary Fringes" Talk given at a conference Formation of Fe precipitates at dynamic redox interfaces and their effect on trace elements 24.02.2014 Karlsruhe, Germany Voegelin Andreas;
11th Swiss Geoscience Meeting Talk given at a conference Composition and structure of fresh and aged Fe oxidation products 15.11.2013 Lausanne, Switzerland Voegelin Andreas; Hug Stephan; Kägi Ralf; Senn Anna-Caterina;
Goldschmidt Conference 2013 Talk given at a conference Arsenic sequestration by fresh and aged Fe oxidation products 25.08.2013 Florence, Italy Voegelin Andreas; Kägi Ralf; Senn Anna-Caterina; Hug Stephan;
Goldschmidt Conference 2013 Talk given at a conference Composition and structure of fresh and aged Fe oxidation products 25.08.2013 Florence, Italy Kägi Ralf; Senn Anna-Caterina; Hug Stephan; Voegelin Andreas;
245th ACS National Meeting Talk given at a conference Formation of iron(III)-phases and redox transformations upon aeration of natural and synthetic groundwaters containing Fe(II), silicate, phosphate, carbonate, and arsenic 07.04.2013 New Orleans, United States of America Voegelin Andreas; Senn Anna-Caterina; Hug Stephan; Kägi Ralf;
6th IBP PhD Congress Poster Effects of dissolved P, Si and Ca on composition, structure and As uptake of fresh and aged Fe precipitates 05.04.2013 Dübendorf, Switzerland Voegelin Andreas; Kägi Ralf; Hug Stephan; Senn Anna-Caterina;
Monte Verità Conference "Iron Biogeochemistry - From Molecular Processes to Global Cycles" Talk given at a conference Dynamic Fe precipitate formation during Fe(II) oxidation in phosphate-containing aqueous solutions 03.03.2013 Ascona, Switzerland Senn Anna-Caterina; Hug Stephan; Voegelin Andreas; Kägi Ralf;
Monte Verità Conference "Iron Biogeochemistry - From Molecular Processes to Global Cycles" Poster Effects of dissolved P, Si and Ca on composition, structure and As uptake of fresh and aged Fe precipitates 03.03.2013 Ascona, Switzerland Voegelin Andreas; Senn Anna-Caterina; Kägi Ralf; Hug Stephan;
10th Swiss Geoscience Meeting Talk given at a conference Dynamic Fe precipitation by Fe(II) oxidation in water 16.11.2012 Bern, Switzerland Senn Anna-Caterina; Hug Stephan; Voegelin Andreas; Kägi Ralf;
10th Swiss Geoscience Meeting Poster Effects of P, Si and Ca on composition, structure and As uptake of fresh and aged Fe precipitates 16.11.2012 Bern, Switzerland Senn Anna-Caterina; Kägi Ralf; Voegelin Andreas;
4th ANKA / KNMF Joint Users Meeting Poster Dynamic Fe precipitate formation during Fe(II) oxidation in aerated phosphate-containing water 10.10.2012 Karlsruhe, Germany Kägi Ralf; Voegelin Andreas; Senn Anna-Caterina; Hug Stephan;
FIMIN-Workshop "Modelling of surface reactions of ferric (hydr)oxides" Poster ffects of dissolved P, Si and Ca on the composition and As uptake of Fe precipitates formed by Fe(II) oxidation by O2 08.10.2012 Bayreuth, Germany Senn Anna-Caterina; Voegelin Andreas; Hug Stephan; Kägi Ralf;
Eurosoil Conference 2012 Poster Phosphate-bearing Fe(III) precipitates forming by Fe(II) oxidation in water 02.07.2012 Bari, Italy Kägi Ralf; Voegelin Andreas; Schwarz Susanne; Hug Stephan;
Goldschmidt Conference 2012 Talk given at a conference Dynamic precipitate formation during Fe(II) oxidation in aerated phosphate-containing water 24.06.2012 Montreal, Canada Voegelin Andreas; Kägi Ralf;
3rd ANKA/KNMF Joint Users Meeting Poster New insight into the formation, structure and aging of iron oxidation products 13.10.2011 Karlsruhe, Germany Hug Stephan; Voegelin Andreas; Kägi Ralf; Schwarz Susanne;
Goldschmidt Conference 2011 Talk given at a conference Nanoparticulate Fe(III)-precipitates forming by Fe(II) oxidation in water 14.08.2011 Prag, Czech Republic Voegelin Andreas; Schwarz Susanne; Hug Stephan; Kägi Ralf;


Associated projects

Number Title Start Funding scheme
113654 Arsenic Contamination of Paddy Soils through Irrigation Water in Bangladesh: Field Evidence and Investigation of Relevant Processes 01.01.2007 Project funding
152993 Iron(III) precipitates formed by iron(II) oxidation in natural waters: Structure, reactivity and impact on arsenic 01.04.2014 Project funding
124411 Diagenetic evolution and mineral composition of Fe/Mn layers in the sediments of Lake Baikal 01.08.2009 Project funding
117933 Dynamics of Trace Metal Speciation in Periodically Reduced Soils 01.03.2008 Project funding

Abstract

The oxidation of ferrous iron (Fe(II)) to ferric iron (Fe(III)) in waters containing phosphate, silicate, calcium (Ca) and trace elements results in short-range-ordered (SRO) Fe(III)-precipitates that control the cycling of major and trace elements at anoxic-oxic boundaries in natural and engineered systems. These precipitates largely vary in composition and degree of Fe(III) polymerization. Their structural diversity and resulting differences in colloidal and chemical behavior however are still poorly understood. Furthermore, although Fe(II) oxidation and Fe(III)-precipitates have long been studied, the full complexity of redox reactions involving Fe(II), reactive oxygen intermediates and trace elements, leading for example to co-oxidation of arsenic (As) and its incorporation into SRO Fe(III)-precipitates, has only received limited attention. The proposed project takes advantage of state-of-the-art synchrotron X-ray absorption spectroscopy (XAS) and analytical electron microscopy (AEM) for the study of SRO Fe(III)-precipitates formed under widely varying chemical conditions. It thereby aims at achieving a new level of understanding regarding the formation, structure and stability of SRO Fe(III)-precipitates and their role in the biogeochemical cycling of major and trace elements. Such mechanistic knowledge is increasingly important for the quantitative description of nutrient and contaminant behavior in aquatic systems and improved water resource use and water treatment. Specifically, the proposed research will focus on the following four research questions:1) How do the kinetics of Fe oxidation, precipitation, and aggregation/coagulation affect the types, structure and nanometer- to micrometer-scale spatial arrangement of SRO Fe(III)-precipitates?2) How does the composition, structure, and morphology of Fe(III)-Ca-phosphates and -arsenates formed by Fe(II) oxidation in presence of phosphate or/and arsenate vary as a function of solution chemistry?3) How does the composition, structure and morphology of different SRO Fe(III)-precipitates change during aging and how do these changes affect their solubility?4) How does Fe oxidation, precipitation and aging affect the co-oxidation and co-transformation of As and what are the implications for As removal in water treatment and for biogeochemical As cycling?To address these questions, Fe(II) (and As(III)) oxidation experiments will be designed that capture the complex interplay of key parameters (concentrations of Fe(II), phosphate, silicate, Ca, As (III) or As(V); solution pH; O2 partial pressure; ionic strength) while being controlled enough to allow for a quantitative description and modeling of the observed processes. XAS will provide molecular-level insight into precipitate structure from the perspective of local element coordination, and AEM into particle composition, structure, and morphology from the nanometer- to the micrometer scale.
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