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| Titel |
Carbon dioxide sequestration via olivine carbonation: Examining the formation of reaction products |
| VerfasserIn |
H. E. King, O. Plümper, A. Putnis |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250021462
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| Zusammenfassung |
| Due to its abundance and natural ability to sequester CO2, olivine has been proposed as one
mineral that could be used in the control of CO2 emissions into the atmosphere (Metz, 2005).
Large scale peridotite deposits found in locations such as the Western Gneiss Region in
Norway could provide in-situ sites for sequestration or the raw materials for ex-situ mineral
carbonation. Determining the conditions under which magnesite (MgCO3) forms
most efficiently is crucial to conduct a cost effective process. Understanding the
development of secondary minerals is particularly important for in-situ methods as
these phases can form passivating layers and affect the host rock porosity. The
final solution of flow-through experiments conducted at alkaline pH have been
shown to be supersaturated with respect to talc and chrysotile (Giammer et al.,
2005), although these phases were not found to have precipitated the formation of a
passivating, amorphous silica layer has been observed on reacted olivine surfaces
(Bearat et al., 2006). By studying magnesite and other products produced during the
carbonation of olivine within Teflon lined steel autoclaves we have begun to form a
more comprehensive understanding of how these reactions would proceed during
sequestration processes. We have performed batch experiments using carbonated saline
solutions in the presence of air or gaseous CO2 from 80 to 200 Ë C. X-ray powder
diffraction was used to identify magnesite within the reaction products. Crystals
of magnesite up to 20 μm in diameter can be observed on olivine grain surfaces
with scanning electron microscopy. Secondary reaction products formed a platy
layer on olivine surfaces in reactions above 160 Ë C and below pH 12. Energy
dispersive X-ray analysis of the platy layer revealed an increase in Fe concentration. The
macroscopically observable red colouration of the reaction products and Raman spectroscopy
indicate that hematite is present in these layers. For experiments with a duration of 4
weeks, lizardite has also been identified using X-ray powder diffraction. The Mg/Si
ratio obtained from energy dispersive X-ray analysis of the secondary phases from
shorter period experiments indicates that lizardite may also be present. However, the
components of these platy layers are closely associated and too low in concentration
to be distinguishable with X-ray diffraction analysis. We have not observed the
precipitation of talc or chrysotile phases in any of our experiments. Amorphous
silica has also not been identified in any of the reaction rims. Higher temperature
experiments and those with an initial solution slightly undersaturated with respect to
magnesite produced well formed carbonate crystals. The presence of CO2 above the
solution did not affect the final magnesite crystal shape but did increase the rate of
precipitation.
References:
Bearat H., McKelvy M. J., Chizmeshya A. V. G., Gormley D., Nunez R., Carpenter R. W.,
Squires K. and Wolf G. H. (2006), Environ. Sci. Technol., 40 4802-4808.
Giammar D. E., Bruant R. G. and Peters C. A. (2005), Chem. Geol., 217 257-276.
Metz B. D. O., de Coninck H., Loos M. and Meyer L. (2005), IPCC Special Report on
Carbon Dioxide Capture and Storage, Cambridge University Press. |
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