skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Changes in the structure of birnessite during siderophore-promoted dissolution: A time-resolved synchrotron X-ray diffraction study

Authors:
; ;
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
Sponsoring Org.:
DOE - OTHERNSF
OSTI Identifier:
1416569
Resource Type:
Journal Article
Resource Relation:
Journal Name: Chemical Geology; Journal Volume: 476; Journal Issue: C
Country of Publication:
United States
Language:
ENGLISH

Citation Formats

Fischer, Timothy B., Heaney, Peter J., and Post, Jeffrey E. Changes in the structure of birnessite during siderophore-promoted dissolution: A time-resolved synchrotron X-ray diffraction study. United States: N. p., 2018. Web. doi:10.1016/j.chemgeo.2017.11.003.
Fischer, Timothy B., Heaney, Peter J., & Post, Jeffrey E. Changes in the structure of birnessite during siderophore-promoted dissolution: A time-resolved synchrotron X-ray diffraction study. United States. doi:10.1016/j.chemgeo.2017.11.003.
Fischer, Timothy B., Heaney, Peter J., and Post, Jeffrey E. 2018. "Changes in the structure of birnessite during siderophore-promoted dissolution: A time-resolved synchrotron X-ray diffraction study". United States. doi:10.1016/j.chemgeo.2017.11.003.
@article{osti_1416569,
title = {Changes in the structure of birnessite during siderophore-promoted dissolution: A time-resolved synchrotron X-ray diffraction study},
author = {Fischer, Timothy B. and Heaney, Peter J. and Post, Jeffrey E.},
abstractNote = {},
doi = {10.1016/j.chemgeo.2017.11.003},
journal = {Chemical Geology},
number = C,
volume = 476,
place = {United States},
year = 2018,
month = 1
}
  • Time-resolved Rietveld refinements using synchrotron X-ray diffraction (XRD) have documented real-time changes in unit-cell parameters in response to cation substitution in synthetic Na-birnessite. Potassium- and Ba-birnessite, like Na-birnessite, were found to have triclinic symmetry. Rietveld analyses of the XRD patterns for K- and Ba-exchanged birnessite revealed decreases in the a, c, and {beta} unit-cell parameters, with a decrease of 1.7 and 0.5%, respectively, in unit-cell volume relative to Na-birnessite. Fourier electron difference syntheses revealed that the changes in the configuration of the interlayer species, and the charge, size, and hydration of the substituting cations, serve as the primary controls onmore » changes in unit-cell parameters. Split electron density maxima with centers at (0 0 0.5) were present for Na, K, and Ba end-members; however, with increased substitution of K{sup +} for Na{sup +}, the axis connecting the split-site maxima rotated from an orientation parallel to the b-axis to along the a-axis. Substitution of Ba{sup 2+} for Na{sup +} did not result in rotation, but splitting of the interlayer site was more pronounced.« less
  • In this study, we applied time-resolved synchrotron X-ray diffraction (TRXRD) to develop kinetic models that test a proposed two-stage reaction pathway for cation exchange in birnessite. These represent the first rate equations calculated for cation exchange in layered manganates. Our previous work has shown that the substitution of K, Cs, and Ba for interlayer Na in synthetic triclinic birnessite induces measurable changes in unit-cell parameters. New kinetic modeling of this crystallographic data supports our previously postulated two-stage reaction pathway for cation exchange, and we can correlate the kinetic steps with changes in crystal structure. In addition, the initial rates ofmore » cation exchange, R ({angstrom}{sup 3} min{sup -1}), were determined from changes in unit-cell volume to follow these rate laws: R = 1.75[K{sup +}{sub (aq)}]{sup 0.56}, R = 41.1[Cs{sup +}{sub (aq)}]{sup 1.10}, R = 1.15[Ba{sup 2+}{sub (aq)}]{sup 0.50}. Thus, the exchange rates for Na in triclinic birnessite decreased in the order: Cs >> K > Ba. These results are likely a function of hydration energy differences of the cations and the preference of the solution phase for the more readily hydrated cation.« less
  • We have explored the exchange of Cs for interlayer Na in birnessite using several techniques, including transmission electron microscopy (TEM) and time-resolved synchrotron X-ray diffraction (XRD). Our goal was to test which of two possible exchange mechanisms is operative during the reaction: (1) diffusion of cations in and out of the interlayer or (2) dissolution of Na-birnessite and reprecipitation of Cs-birnessite. The appearance of distinct XRD peaks for Na- and Cs-rich phases in partially exchanged samples offered support for a simple diffusion model, but it was inconsistent with the compositional and crystallographic homogeneity of (Na,Cs)-birnessite platelets from core to rimmore » as ascertained by TEM. Time-resolved XRD revealed systematic changes in the structure of the emergent Cs-rich birnessite phase during exchange, in conflict with a dissolution and reprecipitation model. Instead, we propose that exchange occurred by sequential delamination of Mn oxide octahedral sheets. Exfoliation of a given interlayer region allowed for wholesale replacement of Na by Cs and was rapidly followed by reassembly. This model accounts for the rapidity of metal exchange in birnessite, the co-existence of distinct Na- and Cs-birnessite phases during the process of exchange, and the uniformly mixed Na- and Cs-compositions ascertained from point analyses by selected area electron diffraction and energy dispersive spectroscopy of partially exchanged grains.« less
  • Recent research has revealed that siderophores, a class of biogenic ligands with high affinities for Fe(III), can also strongly complex Co(III), an element essential to the normal metabolic function of microbes and animals. This study was conducted to quantify the rates and identify the products and mechanisms of the siderophore-promoted dissolution of Co from synthetic Co-bearing minerals. The dissolution reactions of heterogenite (CoOOH) and four Co-substituted goethites (Co-FeOOH) containing different Co concentrations were investigated in the presence of a trihydroxamate siderophore, desferrioxamine B (DFOB), using batch and flow-through experiments. Results showed that DFOB-promoted dissolution of Co from Co-bearing minerals maymore » occur via pH-dependent ligand-promoted or reductive dissolution mechanisms. For heterogenite, ligand-promoted dissolution was the dominant pathway at neutral to alkaline pH, while production of dissolved Co(II) for pH <6. It was not possible from our data to decouple the separate contributions of homogenous and heterogeneous reduction reactions to the aqueous Co(II) pool. Cobalt substitution in Co-substituted goethite, possibly caused by distortion of goethite structure and increased lattice strain, resulted in enhanced total dissolution rates of both Co and Fe. The DFOB-promoted dissolution rates of Co-bearing minerals, coupled with the high affinity of Co(III) for DFOB, suggest that siderophores may be effective for increasing Co solubility, and thus possibly Co bioavailability. The results also suggest that siderophores may contribute to the mobilization of radioactive {sup 60}Co from Co-bearing mineral phases through mineral weathering and dissolution processes.« less