Trace concentration – Huge impact: Nitrate in the calcite/Eu(III) system

Hofmann, Sascha; Voïtchovsky, Kislon; Schmidt, Moritz; Stumpf, Thorsten

doi:10.1016/j.gca.2013.10.008

Cited by 10 publications

(21 citation statements)

References 39 publications

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“…The lifetime of 2450 ± 150 μs here also points at complete loss of hydration in the first coordination sphere of Eu 3+ and therefore an incorporation into the crystal bulk. Comparison of emission spectrum and lifetime clearly identifies β as species B , which had been previously identified in coprecipitation experiments 3 29 .…”

Section: Resultssupporting

confidence: 55%

“…The interaction of Eu 3+ as well as Cm 3+ with calcite synthesized in mixed flow reactors 3 13 29 or formed by mineral phase transition 14 has previously been investigated at the molecular level by site-selective time-resolved laser-induced fluorescence spectroscopy (TRLFS). Here, three main species were identified.…”

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confidence: 99%

“…Studies dedicated to the interaction of Eu 3+ or Cm 3+ with calcite under recrystallization conditions are scarce. Our previous work 29 studied the sorption of Eu 3+ on a single calcite powder in 0.01 mol L −1 NaClO 4 at different contact times, i.e. one day, two weeks and one month at recrystallization conditions.…”

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confidence: 99%

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Incorporation of Eu(III) into Calcite under Recrystallization conditions

Hellebrandt

Hofmann

Jordan

et al. 2016

Sci Rep

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The interaction of calcite with trivalent europium under recrystallization conditions was studied on the molecular level using site-selective time-resolved laser fluorescence spectroscopy (TRLFS). We conducted batch studies with a reaction time from seven days up to three years with three calcite powders, which differed in their specific surface area, recrystallization rates and impurities content. With increase of the recrystallization rate incorporation of Eu3+ occurs faster and its speciation comes to be dominated by one species with its excitation maximum at 578.8 nm, so far not identified during previous investigations of this process under growth and phase transformation conditions. A long lifetime of 3750 μs demonstrates complete loss of hydration, consequently Eu must have been incorporated into the bulk crystal. The results show a strong dependence of the incorporation kinetics on the recrystallization rate of the different calcites. Furthermore the investigation of the effect of different background electrolytes (NaCl and KCl) demonstrate that the incorporation process under recrystallization conditions strongly depends on the availability of Na+. These findings emphasize the different retention potential of calcite as a primary and secondary mineral e.g. in a nuclear waste disposal site.

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Section: Resultssupporting

confidence: 55%

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confidence: 99%

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Incorporation of Eu(III) into Calcite under Recrystallization conditions

Hellebrandt

Hofmann

Jordan

et al. 2016

Sci Rep

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“…For this reason perchlorate salts, particularly sodium perchlorate NaClO 4 , are frequently chosen, due to the perchlorate ion's very weak coordination strength with nearly all cations. However, recent results highlight that even minor changes in the background electrolyte composition can drastically alter the reactivity of a mineral surface (Hofmann et al, 2014). In this study, trace concentrations of NO 3 À in a predominantly ClO 4 À background electrolyte significantly changed the surface morphology of calcite, which in turn affected the uptake of Eu(III) at the interface.…”

Section: Introductionmentioning

confidence: 68%

Effects of the background electrolyte on Th(IV) sorption to muscovite mica

Schmidt

Hellebrandt

Knope

et al. 2015

Geochimica et Cosmochimica Acta

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The adsorption of tetravalent thorium on the muscovite mica (0 0 1) basal plane was studied by X-ray crystal truncation rod (CTR) and resonant anomalous X-ray reflectivity (RAXR) measurements and alpha spectrometry in the presence of perchlorate background electrolytes LiClO 4 , NaClO 4 , and KClO 4 ([Th(IV)] = 0.1 mM, I = 0.1 M or 0.01 M, pH = 3.3 ± 0.3). RAXR data directly reveal a strong influence of the background electrolyte on the actinide sorption. No significant Th adsorption was observed in 0.1 M NaClO 4 , i.e., the Th coverage h(Th), the number of Th per unit cell area of the muscovite surface (A UC = 46.72 Å 2 ), was 60.01 Th/A UC , whereas limited uptake (h(Th) $ 0.04 Th/A UC ) was detected at a lower ionic strength (I = 0.01 M). These results are in stark contrast to the behavior of Th in 0.1 M NaCl which showed a coverage of 0.4 Th/A UC (Schmidt et al., 2012a). Th uptake was also influenced by the electrolyte cation. Weak adsorption was observed in 0.1 M KClO 4 (h(Th) $ 0.07 Th/A UC ) similar to the results in NaClO 4 at lower ionic strength. In contrast, strong adsorption was found in 0.1 M LiClO 4 , with h(Th) = 4.9 Th/A UC , a $10-fold increase compared with that previously reported in NaCl. These differences are confirmed independently by ex situ alpha spectrometry, which shows no measurable Th coverage in 0.1 M NaClO 4 background in contrast to a large coverage of 1.6 Th/A UC in 0.1 M LiClO 4 . Alpha spectrometry cannot be obtained in situ, but sample preparation requires several washing steps that may affect Th(IV) sorption, RAXR, however, is considered to reflect the in situ sorption structure. The CTR/RAXR analyses of Th-LiClO 4 show the sorption structure consisting of Th species that are broadly distributed, centered at heights of 4.1 Å and 29 Å distance from the interface. Neither the very large distribution height of the second species nor the high coverage can be explained with (hydrated) ionic adsorption, suggesting that the enhanced uptake is presumably due to the formation and sorption of Th nanoparticles.

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“…(64) We can, however, reject aragonite formation or recrystallization to calcite as there is (1) no trace of aragonite neither in the XRD analyses ( Figure S1) nor in the Raman spectroscopic spot analyses of the crystal interiors and (2) dominant scalenohedral habit of the crystals, which rules out pseudomorphic recrystallization after aragonite that typically consists of acicular crystals of the orthorhombic system. Trivalent Eu and other trivalent ions (e.g., Am) may be structurally incorporated and replace Ca in the calcite lattice,(65-67) but thermodynamic considerations and spectroscopic results(66, [68][69][70]show that a range of incorporation species and potential endmember phases can be involved.…”

Section: Incorporation Of Metals Into Calcitementioning

confidence: 99%

Incorporation of Metals into Calcite in a Deep Anoxic Granite Aquifer

Drake

Mathurin

Zack

et al. 2018

Environ. Sci. Technol.

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Understanding metal scavenging by calcite in deep aquifers in granite is of importance for deciphering and modeling hydrochemical fluctuations and water-rock interaction in the upper crust and for retention mechanisms associated with underground repositories for toxic wastes. Metal scavenging into calcite has generally been established in the laboratory or in natural environments that cannot be unreservedly applied to conditions in deep crystalline rocks, an environment of broad interest for nuclear waste repositories. Here, we report a microanalytical study of calcite precipitated over a period of 17 years from anoxic, low-temperature (14 °C), neutral (pH: 7.4-7.7), and brackish (Cl: 1700-7100 mg/L) groundwater flowing in fractures at >400 m depth in granite rock. This enabled assessment of the trace metal uptake by calcite under these deep-seated conditions. Aquatic speciation modeling was carried out to assess influence of metal complexation on the partitioning into calcite. The resulting environment-specific partition coefficients were for several divalent ions in line with values obtained in controlled laboratory experiments, whereas for several other ions they differed substantially. High absolute uptake of rare earth elements and U(IV) suggests that coprecipitation into calcite can be an important sink for these metals and analogousactinides in the vicinity of geological repositories.

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Trace concentration – Huge impact: Nitrate in the calcite/Eu(III) system

Cited by 10 publications

References 39 publications

Incorporation of Eu(III) into Calcite under Recrystallization conditions

Incorporation of Eu(III) into Calcite under Recrystallization conditions

Effects of the background electrolyte on Th(IV) sorption to muscovite mica

Incorporation of Metals into Calcite in a Deep Anoxic Granite Aquifer

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