Structural response of phyllomanganates to wet aging and aqueous Mn(II)
Journal Article
·
· Geochimica et Cosmochimica Acta
- Washington Univ., St. Louis, MO (United States); DOE Office of Scientific and Technical Information (OSTI)
- Washington Univ., St. Louis, MO (United States)
Naturally occurring Mn(IV/III) oxides are often formed through microbial Mn(II) oxidation, resulting in reactive phyllomanganates with varying Mn(IV), Mn(III), and vacancy contents. Residual aqueous Mn(II) may adsorb in the interlayer of phyllomanganates above vacancies in their octahedral sheets. The potential for interlayer Mn(II)-layer Mn(IV) comproportionation reactions and subsequent formation of structural Mn(III) suggests that aqueous Mn(II) may cause phyllomanganate structural changes that alters mineral reactivity or trace metal scavenging. Here we examine the effects of aging phyllomanganates with varying initial vacancy and Mn(III) content in the presence and absence of dissolved Mn(II) at pH 4 and 7. Three phyllomanganates were studied: two exhibiting turbostratic layer stacking (δ-MnO2 with high vacancy content and hexagonal birnessite with both vacancies and Mn(III) substitutions) and one with rotationally ordered layer stacking (triclinic birnessite containing predominantly Mn(III) substitutions). Structural analyses suggest that during aging at pH 4, Mn(II) adsorbs above vacancies and promotes the formation of phyllomanganates with rotationally ordered sheets and mixed symmetries arranged into supercells, while structural Mn(III) undergoes disproportionation. These structural changes at pH 4 correlate with reduced Mn(II) uptake onto triclinic and hexagonal birnessite after 25 days relative to 48 h of reaction, indicating that phyllomanganate reactivity decreases upon aging with Mn(II), or that recrystallization processes involving Mn(II) uptake occur over 25 days. At pH 7, Mn(II) adsorbs and causes limited structural effects, primarily increasing sheet stacking in δ-MnO2. These results show that aging-induced structural changes in phyllomanganates are affected by aqueous Mn(II), pH, and initial solid-phase Mn(III) content. In conclusion, such restructuring likely alters manganese oxide reactions with other constituents in environmental and geologic systems, particularly trace metals and redox-active compounds.
- Research Organization:
- Washington Univ., St. Louis, MO (United States). School of Medicine
- Sponsoring Organization:
- National Science Foundation; USDOE
- Grant/Contract Number:
- AC02-06CH11357
- OSTI ID:
- 1418531
- Alternate ID(s):
- OSTI ID: 1306611
OSTI ID: 1432896
- Journal Information:
- Geochimica et Cosmochimica Acta, Journal Name: Geochimica et Cosmochimica Acta Journal Issue: C Vol. 192; ISSN 0016-7037
- Publisher:
- The Geochemical Society; The Meteoritical SocietyCopyright Statement
- Country of Publication:
- United States
- Language:
- English
Characterization of manganese oxide amendments for in situ remediation of mercury-contaminated sediments
|
journal | January 2018 |
Impact of dissolved O 2 on phenol oxidation by δ-MnO 2
|
journal | January 2019 |
Similar Records
Impact of Mn(II)-Manganese Oxide Reactions on Ni and Zn Speciation
Molecular simulations of hydrated phyllomanganates
Structural Transformation of Birnessite by Fulvic Acid under Anoxic Conditions
Journal Article
·
Tue Feb 28 19:00:00 EST 2017
· Environmental Science and Technology
·
OSTI ID:1418550
Molecular simulations of hydrated phyllomanganates
Journal Article
·
Thu May 31 20:00:00 EDT 2018
· Geochimica et Cosmochimica Acta
·
OSTI ID:1543544
Structural Transformation of Birnessite by Fulvic Acid under Anoxic Conditions
Journal Article
·
Sun Jan 21 19:00:00 EST 2018
· Environmental Science and Technology
·
OSTI ID:1424770