The role of magnesium in stabilising amorphous calcium carbonate and controlling calcite morphologies

By E. Loste, R. Wilson, R. Seshadri, F. Meldrum. 2003

537 citations recorded by the source corpus.

Abstract Calcium carbonate has been precipitated from aqueous solutions containing magnesium under conditions of high supersaturation. The precipitates were analysed over time using X-ray diffraction (XRD) and Infrared Spectroscopy (IR), and it was demonstrated that in all cases amorphous calcium carbonate (ACC) was the first phase formed. The magnesium content of the ACC was defined by the Mg:Ca ratio in the solution, and increased systematically with increasing Mg:Ca. In turn, ACC occluding higher magnesium concentrations was significantly more stable than low magnesium ACC. The crystalline phase produced on transformation of ACC depended on the Mg:Ca ratio, and ACC precipitated from solutions containing higher Mg concentrations crystallised to yield high-Mg calcites (occluding up to 47 mol% Mg), together with CaCO3.H2O and/or CaCO3.6H2O. The magnesium content of the ACC phase also directly affected the final morphology of the precipitates, such that continuous sheets of CaCO3 were produced at the air/solution interface at solution ratios of 3:1 Mg:Ca and above. Previously, this effect has only been observed for ACC stabilised with organic additives. These results have relevance to the mechanism of formation of biological magnesian calcites, and suggest that the stabilisation of ACC by magnesium may provide organisms with a mechanism for controlling crystal morphologies.

Subfields: Biomaterials, Biomedical Engineering, Paleontology

View Paper: https://www.semanticscholar.org/paper/23e0a71b3757da606a12a1dc3773035b69e00b6c

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In Biomaterials

1. J. Rodriguez-Blanco
2. S. Shaw
3. L. Benning
4. J. Provis
5. S. A. Bernal
6. J. V. van Deventer

In Biomedical Engineering

1. J. Rodriguez-Blanco
2. L. Benning
3. J. V. van Deventer
4. S. Shaw
5. S. A. Bernal
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In Paleontology

1. J. Rodriguez-Blanco
2. L. Benning
3. S. Shaw

Citations in the corpus

• A route for the direct crystallization of dolomite (2015, background): “This is consistent with studies that showed a direct proportionality between Mg content and crystallization induction time in the calcium carbonate system (e.g., calcite formation; Reddy and Nancollas 1976; Tracy et al. 1998a, 1998b; Loste et al. 2003; Raz et al. 2003).”
• The role of Mg in the crystallization of monohydrocalcite (2014, background): “…with increasing Mg contents is not unexpected, and confirms both abiotic (Ajikumar et al., 2005; Rodriguez-Blanco et al., 2011, 2009) and biotic (Loste et al., 2003; Raz et al., 2003; Politi et al., 2010) data that demonstrate the importance of Mg in stabilizing amorphous precursors and…”
• Alkali-activated slag cements produced with a blended sodium carbonate/sodium silicate activator (2016, background): “Magnesium has a significant influence on calcium carbonate precipitation, and can stabilise amorphous carbonates, aragonite and/or vaterite when its concentration is sufficiently high (Falini et al., 1996; Loste et al., 2003).”