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Article

Effect of pH and Type of Stirring on the Spontaneous Precipitation of CaCO3 at Identical Initial Supersaturation, Ionic Strength and a(Ca2+)/a(CO32−) Ratio

1
Laboratory for Precipitation Processes, Division of Materials Chemistry, Ruđer Bošković Institute, Bijenička cesta 54, 10000 Zagreb, Croatia
2
Faculty of Science, University of Zagreb, Horvatovac 102A, 10000 Zagreb, Croatia
*
Author to whom correspondence should be addressed.
Academic Editor: Francesco Capitelli
Crystals 2021, 11(9), 1075; https://doi.org/10.3390/cryst11091075
Received: 30 July 2021 / Revised: 26 August 2021 / Accepted: 3 September 2021 / Published: 5 September 2021
(This article belongs to the Special Issue Green Approach in Synthesis of Bio-Inspired Materials)
CaCO3 precipitation is physical-chemical basis of biomineral formation of hard tissue (shells, skeletons) in marine calcifying organisms (=biomineralization). Processes controlling biomineralization are still not fully clarified, so the study of influence of pH on basic processes of CaCO3 precipitation should contribute to better understanding of biomineralization under climate change. This paper reports on the effect of initial pH (pH0) and type of stirring (mechanical and magnetical) on spontaneous precipitation and phase composition, size and morphology of spontaneously precipitated CaCO3 formed at the identical initial supersaturation, ionic strength and a(Ca2+)/a(CO32−) ratio. The initial pH varied in a range 8.50 ≤ pH0 ≤ 10.50 and included values relevant for mimicking the conditions related to biomineralization in marine organisms. In all systems two CaCO3 polymorphs were found: calcite and/or vaterite. The increase of pH0 favoured the formation of rhombohedral calcite no matter the type of stirring. This was exclusively influenced by the systems’ pH0 (other relevant initial parameters were identical). Furthermore, increase of pH0 caused change of vaterite morphology from cauliflower-like spheroids to regular spherulites. The mechanically stirred systems produced larger calcite and vaterite particles and higher content of calcite. View Full-Text
Keywords: calcium carbonate; biomineralization; spontaneous precipitation; pH; stirring; calcite; vaterite calcium carbonate; biomineralization; spontaneous precipitation; pH; stirring; calcite; vaterite
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MDPI and ACS Style

Kontrec, J.; Tomašić, N.; Matijaković Mlinarić, N.; Kralj, D.; Njegić Džakula, B. Effect of pH and Type of Stirring on the Spontaneous Precipitation of CaCO3 at Identical Initial Supersaturation, Ionic Strength and a(Ca2+)/a(CO32−) Ratio. Crystals 2021, 11, 1075. https://doi.org/10.3390/cryst11091075

AMA Style

Kontrec J, Tomašić N, Matijaković Mlinarić N, Kralj D, Njegić Džakula B. Effect of pH and Type of Stirring on the Spontaneous Precipitation of CaCO3 at Identical Initial Supersaturation, Ionic Strength and a(Ca2+)/a(CO32−) Ratio. Crystals. 2021; 11(9):1075. https://doi.org/10.3390/cryst11091075

Chicago/Turabian Style

Kontrec, Jasminka, Nenad Tomašić, Nives Matijaković Mlinarić, Damir Kralj, and Branka Njegić Džakula. 2021. "Effect of pH and Type of Stirring on the Spontaneous Precipitation of CaCO3 at Identical Initial Supersaturation, Ionic Strength and a(Ca2+)/a(CO32−) Ratio" Crystals 11, no. 9: 1075. https://doi.org/10.3390/cryst11091075

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