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| Titel |
Calcite crystallization in the presence of europium: Preliminary results |
| VerfasserIn |
Aikaterini Vavouraki, Ángeles Fernández-González, Manuel Prieto |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250031846
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| Zusammenfassung |
| Ubiquitous calcite is found in natural abiogenic and biogenic environments. Europium
radionuclide is enlisted as a rare Earth element and frequently occurs in natural samples of
calcite. In this study two complementary crystallization methods are tested to investigate
possible conditions of europium uptake by calcite. Counter-diffusion-reaction of
(Ca2+, Eu3+) and (Na+, CO32-) ions through a porous silica gel (Prieto et al., 1997) was
used to examine possible Ca-Eu-Na carbonate solid solution formation. A variety of calcium,
carbonate and europium aqueous solution compositions were prepared at high supersaturation
with respect to calcite. Crystallization in gel media enables to improve crystal size and
facilitates with its characterization. Here, polymorphs of calcium carbonate were obtained in
the presence of europium in one month duration gel experiments. An alternative quick
method of crystallizing calcium carbonate is the method of vapour diffusion on a
crystallization mushroom (Hernández-Hernández et al., 2008). Ammonium bicarbonate
solution releases NH3(g) and CO2(g) and in a sitting drop of calcium chloride, nucleation of
calcium carbonate is observed. In both diffusion processes calcite crystals and its polymorphs
of aragonite and vaterite were obtained and analyzed by scanning electron microscopy
(SEM-EDS) and microprobe (EMP). Crystals exhibited a wide variety of forms as
a function of the europium mole fraction (XEu,aq.) in the aqueous solution. At
XEu,aq. = 0.02 trace of europium was detected into solid calcite crystal structure. This
study examines calcite as a potential host mineral for radionuclide deposits such as
europium.
References
Prieto, M. et al., 1997. Geochim. Cosmochim. Acta 61, 3383–3397.
Hernández-Hernández, A. et al., 2008. J. Crystal Growth 310, 1754–1759. |
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