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The effect of silica on polymorphic precipitation of calcium carbonate : an on-line energy-dispersive X-ray diffraction (EDXRD) study

The effect of silica on polymorphic precipitation of calcium carbonate : an on-line energy-dispersive X-ray diffraction (EDXRD) study

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KELLERMEIER, Matthias, Fabian GLAAB, Regina KLEIN, Emilio MELERO-GARCÍA, Werner KUNZ, Juan Manuel GARCÍA-RUIZ, 2013. The effect of silica on polymorphic precipitation of calcium carbonate : an on-line energy-dispersive X-ray diffraction (EDXRD) study. In: Nanoscale. 5(15), pp. 7054-7065. ISSN 2040-3364. eISSN 2040-3372. Available under: doi: 10.1039/c3nr00301a

@article{Kellermeier2013-08-07effec-42078, title={The effect of silica on polymorphic precipitation of calcium carbonate : an on-line energy-dispersive X-ray diffraction (EDXRD) study}, year={2013}, doi={10.1039/c3nr00301a}, number={15}, volume={5}, issn={2040-3364}, journal={Nanoscale}, pages={7054--7065}, author={Kellermeier, Matthias and Glaab, Fabian and Klein, Regina and Melero-García, Emilio and Kunz, Werner and García-Ruiz, Juan Manuel} }

Kunz, Werner García-Ruiz, Juan Manuel Melero-García, Emilio eng 2013-08-07 Glaab, Fabian Kellermeier, Matthias 2018-04-18T09:19:58Z Klein, Regina The effect of silica on polymorphic precipitation of calcium carbonate : an on-line energy-dispersive X-ray diffraction (EDXRD) study García-Ruiz, Juan Manuel Kunz, Werner Kellermeier, Matthias Melero-García, Emilio 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 °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 °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 CaCO<sub>3</sub> precipitation scenarios in both geochemical and industrial settings, where solution silicate is omnipresent, as well as for CO<sub>2</sub> sequestration technologies. Klein, Regina Glaab, Fabian 2018-04-18T09:19:58Z

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