A time-resolved X-ray diffraction study of Cs exchange into hexagonal H-birnessite

Claire R. Fleeger, Peter J. Heaney, Jeffrey E. Post

Research output: Contribution to journalArticle

11 Citations (Scopus)

Abstract

To measure the uptake of radioactive Cs in soils that are rich in Mn oxides, we applied time-resolved synchrotron X-ray diffraction (TR-XRD), inductively coupled plasma-mass spectrometry (ICP-MS), and analytical scanning electron microscopy (SEM) to determine the kinetics and mechanisms of aqueous Cs substitution in the phyllomanganate hexagonal H-birnessite at pH values ranging from 3 to 10. We observed that the rate of Cs cation exchange into hexagonal H-birnessite exhibited only a weak dependence on pH, but the total amount of Cs loading in the interlayer region increased dramatically above pH 6.5. The increase in Cs content at higher pH may be attributed to the increasingly negative charge on the Mn-O octahedral sheets and perhaps to a structural change toward triclinic symmetry with high pH. Dissolution at low pH may have inhibited Cs sequestration. Our work supports delamination-reassembly as a mechanism of cation exchange.

Original languageEnglish (US)
Pages (from-to)671-679
Number of pages9
JournalAmerican Mineralogist
Volume98
Issue number4
DOIs
StatePublished - Apr 1 2013

Fingerprint

birnessite
Cations
ion exchange
X-ray diffraction
X ray diffraction
Inductively coupled plasma mass spectrometry
delamination
Synchrotrons
diffraction
Delamination
structural change
Oxides
symmetry
Dissolution
substitution
x rays
Substitution reactions
mass spectrometry
scanning electron microscopy
dissolution

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Geochemistry and Petrology

Cite this

Fleeger, Claire R. ; Heaney, Peter J. ; Post, Jeffrey E. / A time-resolved X-ray diffraction study of Cs exchange into hexagonal H-birnessite. In: American Mineralogist. 2013 ; Vol. 98, No. 4. pp. 671-679.
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A time-resolved X-ray diffraction study of Cs exchange into hexagonal H-birnessite. / Fleeger, Claire R.; Heaney, Peter J.; Post, Jeffrey E.

In: American Mineralogist, Vol. 98, No. 4, 01.04.2013, p. 671-679.

Research output: Contribution to journalArticle

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AB - To measure the uptake of radioactive Cs in soils that are rich in Mn oxides, we applied time-resolved synchrotron X-ray diffraction (TR-XRD), inductively coupled plasma-mass spectrometry (ICP-MS), and analytical scanning electron microscopy (SEM) to determine the kinetics and mechanisms of aqueous Cs substitution in the phyllomanganate hexagonal H-birnessite at pH values ranging from 3 to 10. We observed that the rate of Cs cation exchange into hexagonal H-birnessite exhibited only a weak dependence on pH, but the total amount of Cs loading in the interlayer region increased dramatically above pH 6.5. The increase in Cs content at higher pH may be attributed to the increasingly negative charge on the Mn-O octahedral sheets and perhaps to a structural change toward triclinic symmetry with high pH. Dissolution at low pH may have inhibited Cs sequestration. Our work supports delamination-reassembly as a mechanism of cation exchange.

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