Kellermeier, Matthias and Glaab, Fabian and Klein, Regina and Melero-Garcia, Emilio and Kunz, Werner and Garcia Ruiz, Juan Manuel (2013) The effect of silica on polymorphic precipitation of calcium carbonate: an on-line energy-dispersive X-ray diffraction (EDXRD) study. NANOSCALE, 5 (15). pp. 7054-7065. ISSN 2040-3364, 2040-3372
Full text not available from this repository. (Request a copy)Abstract
Calcium carbonate is the most abundant biomineral and a compound of great industrial importance. Its precipitation from solution has been studied extensively and was often shown to proceed via distinct intermediate phases, which undergo sequential transformations before eventually yielding the stable crystalline polymorph, calcite. In the present work, we have investigated the crystallisation of calcium carbonate in a time-resolved and non-invasive manner by means of energy-dispersive X-ray diffraction (EDXRD) using synchrotron radiation. In particular, the role of silica as a soluble additive during the crystallisation process was examined. Measurements were carried out at different temperatures (20, 50 and 80 degrees C) and various silica concentrations. Experiments conducted in the absence of silica reflect the continuous conversion of kinetically formed metastable polymorphs (vaterite and aragonite) to calcite and allow for quantifying the progress of transformation. Addition of silica induced remarkable changes in the temporal evolution of polymorphic fractions existing in the system. Essentially, the formation of calcite was found to be accelerated at 20 degrees C, whereas marked retardation or complete inhibition of phase transitions was observed at higher temperatures. These findings are explained in terms of a competition between the promotional effect of silica on calcite growth rates and kinetic stabilisation of vaterite and aragonite due to adsorption (or precipitation) of silica on their surfaces, along with temperature-dependent variations of silica condensation rates. Data collected at high silica concentrations indicate the presence of an amorphous phase over extended frames of time, suggesting that initially generated ACC particles are progressively stabilised by silica. Our results may have important implications for CaCO3 precipitation scenarios in both geochemical and industrial settings, where solution silicate is omnipresent, as well as for CO2 sequestration technologies.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | SELF-ORGANIZED FORMATION; HOMOGENEOUS PRECIPITATION; WOLLASTONITE CARBONATION; PRENUCLEATION CLUSTERS; RICH ENVIRONMENTS; DISSOLVED SILICA; AQUEOUS-SOLUTION; CRYSTAL-GROWTH; ARAGONITE; VATERITE; |
| Subjects: | 500 Science > 540 Chemistry & allied sciences |
| Divisions: | Chemistry and Pharmacy > Institut für Physikalische und Theoretische Chemie > Chair of Chemistry VI - Physical Chemistry (Solution Chemistry) > Prof. Dr. Werner Kunz |
| Depositing User: | Dr. Gernot Deinzer |
| Date Deposited: | 28 Apr 2020 13:45 |
| Last Modified: | 28 Apr 2020 13:45 |
| URI: | https://pred.uni-regensburg.de/id/eprint/17395 |
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