Mode of incorporation of Sr2+ in calcite: Determination by X-ray absorption spectroscopy

Pingitore, Nicholas E.; Lytle, F. W.; Davies, Brian M.; Eastman, Michael P.; Eller, P. G.; Larson, E. M.

doi:10.1016/0016-7037(92)90222-5

Cited by 106 publications

(46 citation statements)

References 16 publications

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“…Our spectra were similar to those reported by Pingitore et al (1992) in their study of Sr incorporation into natural and synthetic calcites. Pingitore et al (1992) interpreted their spectra as evidence for Sr substitution at Ca structural sites.…”

Section: Sr Coordination In Calcitesupporting

confidence: 89%

“…Pingitore et al (1992) interpreted their spectra as evidence for Sr substitution at Ca structural sites. In an EXAFS analysis of calcite, strontianite, and samples of Sr coprecipitated with CaCO 3 , Parkman et al (1998) verified an approximately hexacoordinate structure for strontium in the calcite lattice.…”

Section: Sr Coordination In Calcitementioning

confidence: 99%

“…XANES analyses indicate that the Sr incorporated into calcite through the activity of urea hydrolyzing organisms is present in the form of a solid solution, ensuring the relative stability of 90 Sr immobilized in calcite through this mechanism. As Pingitore et al (1992) point out, "no significant alteration of the strontium in geological calcites should occur, barring the actual dissolution of the material." This robustness bodes well for the potential application of the proposed remediation approach as a long-term containment and stabilization strategy for 90 Sr in environments such as the SRPA where calcite is stable.…”

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confidence: 99%

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Strontium incorporation into calcite generated by bacterial ureolysis

Fujita

Redden

Ingram

et al. 2004

Geochimica et Cosmochimica Acta

214

141

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Abstract-Strontium incorporation into calcite generated by bacterial ureolysis was investigated as part of an assessment of a proposed remediation approach for 90 Sr contamination in groundwater. Urea hydrolysis produces ammonium and carbonate and elevates pH, resulting in the promotion of calcium carbonate precipitation. Urea hydrolysis by the bacterium Bacillus pasteurii in a medium designed to mimic the chemistry of the Snake River Plain Aquifer in Idaho resulted in a pH rise from 7.5 to 9.1. Measured average distribution coefficients (D EX ) for Sr in the calcite produced by ureolysis (0.5) were up to an order of magnitude higher than values reported in the literature for natural and synthetic calcites (0.02-0.4). They were also higher than values for calcite produced abiotically by ammonium carbonate addition (0.3). The precipitation of calcite in these experiments was verified by X-ray diffraction. Time-of-flight secondary ion mass spectrometry (ToF SIMS) depth profiling (up to 350 nm) suggested that the Sr was not merely sorbed on the surface, but was present at depth within the particles. X-ray absorption near edge spectra showed that Sr was present in the calcite samples as a solid solution. The extent of Sr incorporation appeared to be driven primarily by the overall rate of calcite precipitation, where faster precipitation was associated with greater Sr uptake into the solid. The presence of bacterial surfaces as potential nucleation sites in the ammonium carbonate precipitation treatment did not enhance overall precipitation or the Sr distribution coefficient. Because bacterial ureolysis can generate high rates of calcite precipitation, the application of this approach is promising for remediation of 90 Sr contamination in environments where calcite is stable over the long term.

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Section: Sr Coordination In Calcitesupporting

confidence: 89%

Section: Sr Coordination In Calcitementioning

confidence: 99%

mentioning

confidence: 99%

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Strontium incorporation into calcite generated by bacterial ureolysis

Fujita

Redden

Ingram

et al. 2004

Geochimica et Cosmochimica Acta

214

141

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“…However, the question remains as to whether larger ions, such as Ba and Pb, achieve similar coordination. An XAFS study of Sr incorporation in calcite indicates that octahedral coordination is indeed possible for that ion [16]. …”

Section: Discussionmentioning

confidence: 99%

Characterization of Heavy Metal Incorporation in Calcite by XAFS Spectroscopy

1997

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Zn and Co K-edge XAFS have been analyzed for spectra obtained from synthetic calcite that incorporated trace amounts of zn2+ and co2+ during growth from aqueous solutions at room temperature. Zn and Co concentrations in the calcite ranged from 250 to 2150 ppm. Analysis of the first shells indicates that the immediate coordination of both metal ions is approximately six oxygens at 2.11-2.12 A. These results are consistent with octahedral coordination at the unique Ca site in calcite. The observation that Co and Zn attain similar coordination in the bulk following incorporation suggests that their strongly contrasting surface site preferences are not expressed after being buried by subsequent growth layers.

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“…Traditionally, optimized geometries and charge densities, rather than energies, have been evaluated for incorporated systems (e.g., [9,21,22]). Quantum-mechanically optimized geometries are compared with experimental measurements, such as extended X-ray absorption fine structure (EXAFS) measurements, to identify coordination environments and distances to nearest neighbors.…”

Section: Previous Approachesmentioning

confidence: 99%

Quantum-Mechanical Methods for Quantifying Incorporation of Contaminants in Proximal Minerals

et al. 2014

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Abstract:Incorporation reactions play an important role in dictating immobilization and release pathways for chemical species in low-temperature geologic environments. Quantum-mechanical investigations of incorporation seek to characterize the stability and geometry of incorporated structures, as well as the thermodynamics and kinetics of the reactions themselves. For a thermodynamic treatment of incorporation reactions, a source of the incorporated ion and a sink for the released ion is necessary. These sources/sinks in a real geochemical system can be solids, but more commonly, they are charged aqueous species. In this contribution, we review the current methods for ab initio calculations of incorporation reactions, many of which do not consider incorporation from aqueous species. We detail a recently-developed approach for the calculation of incorporation reactions and expand on the part that is modeling the interaction of periodic solids with aqueous source and sink phases and present new research using this approach. To model these interactions, a systematic series of calculations must be done to transform periodic solid source and sink phases to aqueous-phase clusters. Examples of this process are provided for three case studies: (1) neptunyl incorporation into studtite and boltwoodite: for the layered boltwoodite, the incorporation energies are smaller (more favorable) for reactions using environmentally relevant source and sink phases (i.e., ΔE rxn (oxides) > ΔE rxn (silicates) > ΔE rxn (aqueous)). Estimates of the solid-solution behavior of Np to predict the limit of Np-incorporation into boltwoodite (172 and 768 ppm at 300 °C, respectively); (2) uranyl and neptunyl incorporation into carbonates and sulfates: for both carbonates and sulfates, it was found that actinyl incorporation into a defect site is more favorable than incorporation into defect-free periodic structures. In addition, actinyl incorporation into carbonates with aragonite structure is more favorable than into carbonates with calcite structure; and (3)

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Mode of incorporation of Sr2+ in calcite: Determination by X-ray absorption spectroscopy

Cited by 106 publications

References 16 publications

Strontium incorporation into calcite generated by bacterial ureolysis

Strontium incorporation into calcite generated by bacterial ureolysis

Characterization of Heavy Metal Incorporation in Calcite by XAFS Spectroscopy

Quantum-Mechanical Methods for Quantifying Incorporation of Contaminants in Proximal Minerals

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