Reductive dissolution of manganese (IV) oxides and precipitation of iron (III) : implications for redox processes in an alluvial aquifer affected by acid mine drainage

Persistent Link:
http://hdl.handle.net/10150/191257
Title:
Reductive dissolution of manganese (IV) oxides and precipitation of iron (III) : implications for redox processes in an alluvial aquifer affected by acid mine drainage
Author:
Villinski, John Eugene.
Issue Date:
2001
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
The processes that control the reductive dissolution of Mn0₂ by Fe(II) under conditions simulating the effects of acid mine drainage on subsurface environments and the subsequent precipitation of Fe(III) has been investigated. Results from real-time, in situ X-ray absorption spectroscopy (XAS) flow-through reaction cell studies indicate that a mixed Fe/Mn solid phase with the local structure of the spinel mineral jacobsite (MnFe₂O₄) is formed after the Mn0₂ surfaces are coated with ferric precipitates. In the absence of previously precipitated Fe(III), no reduced manganese solid is formed. The ferric precipitates do not incorporate significant quantities of Mn(II) down gradient from the reactive Fe(II) front. The maximum amount of the original Mn0₂ incorporated into this jacobsite-like solid is 5%. Results from batch experiments showed similar results compared to the flow-through experiments, with an initially fast rate of Mn(II) release, followed by a much slower release after 5-10 min had elapsed. The reaction products, Fe(III)(aq) and Fe(III)(s) were found to decrease the initial reaction rate. A simple model was developed to describe the temporal concentrations of Mn(II)(aq), Fe(II)(aq), and Fe(III)(aq) that include a Langmurian blocking function to describe the effects of the ferric reaction products on the reaction rate. The model also allowed for a second order process to occur at long time that was dependent solely on the aqueous concentrations of Fe(II) and Mn02. The formation of the ferric reaction products were found to transform from aqueous sulfate complexes to (presumable) ternary surface complexes with sulfate. Within 10 h, these precipitates may have formed chains of edge-sharing octahedra on the order of 60 Å. The precipitates have large amount of sulfate associated with them, which may preclude the formation of ferrihydrite, and may indicate the formation of schwertmannite. The average Fe:SO₄ ratio was 4.4 ± 1.0, a value similar to that reported for schwertmannite. The presence of goethite was identified by X-ray diffraction as early as 50 d, indicating that sulfate is being excluded from the precipitates. The release of Mn(II), FeT, and sulfate was controlled by diffusion, which may also be the process that controls the rate of transformation.
Type:
Dissertation-Reproduction (electronic); text
Keywords:
Hydrology.; Manganese oxides -- Arizona -- Pinal Creek.; Oxidation-reduction reaction -- Environmental aspects.; Acid mine drainage -- Environmental aspects -- Arizona -- Pinal Creek Watershed.
Degree Name:
Ph. D.
Degree Level:
doctoral
Degree Program:
Hydrology and Water Resources; Graduate College
Degree Grantor:
University of Arizona
Committee Chair:
Conklin, Martha H.

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titleReductive dissolution of manganese (IV) oxides and precipitation of iron (III) : implications for redox processes in an alluvial aquifer affected by acid mine drainageen_US
dc.creatorVillinski, John Eugene.en_US
dc.contributor.authorVillinski, John Eugene.en_US
dc.date.issued2001en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractThe processes that control the reductive dissolution of Mn0₂ by Fe(II) under conditions simulating the effects of acid mine drainage on subsurface environments and the subsequent precipitation of Fe(III) has been investigated. Results from real-time, in situ X-ray absorption spectroscopy (XAS) flow-through reaction cell studies indicate that a mixed Fe/Mn solid phase with the local structure of the spinel mineral jacobsite (MnFe₂O₄) is formed after the Mn0₂ surfaces are coated with ferric precipitates. In the absence of previously precipitated Fe(III), no reduced manganese solid is formed. The ferric precipitates do not incorporate significant quantities of Mn(II) down gradient from the reactive Fe(II) front. The maximum amount of the original Mn0₂ incorporated into this jacobsite-like solid is 5%. Results from batch experiments showed similar results compared to the flow-through experiments, with an initially fast rate of Mn(II) release, followed by a much slower release after 5-10 min had elapsed. The reaction products, Fe(III)(aq) and Fe(III)(s) were found to decrease the initial reaction rate. A simple model was developed to describe the temporal concentrations of Mn(II)(aq), Fe(II)(aq), and Fe(III)(aq) that include a Langmurian blocking function to describe the effects of the ferric reaction products on the reaction rate. The model also allowed for a second order process to occur at long time that was dependent solely on the aqueous concentrations of Fe(II) and Mn02. The formation of the ferric reaction products were found to transform from aqueous sulfate complexes to (presumable) ternary surface complexes with sulfate. Within 10 h, these precipitates may have formed chains of edge-sharing octahedra on the order of 60 Å. The precipitates have large amount of sulfate associated with them, which may preclude the formation of ferrihydrite, and may indicate the formation of schwertmannite. The average Fe:SO₄ ratio was 4.4 ± 1.0, a value similar to that reported for schwertmannite. The presence of goethite was identified by X-ray diffraction as early as 50 d, indicating that sulfate is being excluded from the precipitates. The release of Mn(II), FeT, and sulfate was controlled by diffusion, which may also be the process that controls the rate of transformation.en_US
dc.description.notehydrology collectionen_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.typetexten_US
dc.subjectHydrology.en_US
dc.subjectManganese oxides -- Arizona -- Pinal Creek.en_US
dc.subjectOxidation-reduction reaction -- Environmental aspects.en_US
dc.subjectAcid mine drainage -- Environmental aspects -- Arizona -- Pinal Creek Watershed.en_US
thesis.degree.namePh. D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineHydrology and Water Resourcesen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.chairConklin, Martha H.en_US
dc.contributor.committeememberBales, Roger C.en_US
dc.contributor.committeememberFernando, Quintusen_US
dc.contributor.committeememberPemberton, Jeanne E.en_US
dc.contributor.committeememberO'Day, Peggy A.en_US
dc.identifier.oclc225920817en_US
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