Impact of Mn(II)-Manganese Oxide Reactions on Ni and Zn Speciation
Journal Article
·
· Environmental Science and Technology
- Washington Univ., Saint Louis, MO (United States); DOE OSTI
- Washington Univ., Saint Louis, MO (United States)
- Washington Univ., St. Louis, MO (United States)
Layered Mn oxide minerals (phyllomanganates) often control trace metal fate in natural systems. The strong uptake of metals such as Ni and Zn by phyllomanganates results from adsorption on or incorporation into vacancy sites. Mn(II) also binds to vacancies and subsequent comproportionation with structural Mn(IV) may alter sheet structures by forming larger and distorted Mn(III)O6 octahedra. Such Mn(II)-phyllomanganate reactions may thus alter metal uptake by blocking key reactive sites. Here we investigate the effect of Mn(II) on Ni and Zn binding to phyllomanganates of varying initial vacancy content (δ-MnO2, hexagonal birnessite, and triclinic birnessite) at pH 4 and 7 under anaerobic conditions. Dissolved Mn(II) decreases macroscopic Ni and Zn uptake at pH 4 but not pH 7. Extended X-ray absorption fine structure spectroscopy demonstrates that decreased uptake at pH 4 corresponds with altered Ni and Zn adsorption mechanisms. These metals transition from binding in the interlayer to sheet edges, with Zn increasing its tetrahedrally coordinated fraction. These effects on metal uptake and binding correlate with Mn(II)-induced structural changes, which are more substantial at pH 4 than 7. Finally, through these structural effects and the pH-dependence of Mn(II)-metal competitive adsorption, system pH largely controls metal binding to phyllomanganates in the presence of dissolved Mn(II).
- Research Organization:
- Washington Univ., Saint Louis, MO (United States)
- Sponsoring Organization:
- National Science Foundation (NSF); USDOE Office of Science (SC)
- Grant/Contract Number:
- AC02-06CH11357; AC02-76SF00515
- OSTI ID:
- 1418550
- Journal Information:
- Environmental Science and Technology, Journal Name: Environmental Science and Technology Journal Issue: 6 Vol. 51; ISSN 0013-936X
- Publisher:
- American Chemical Society (ACS)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
Characterization of manganese oxide amendments for in situ remediation of mercury-contaminated sediments
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journal | January 2018 |
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