Controlling CaCO3 particle size with {Ca2+}:{CO32-} ratios in aqueous environments

Sergej Seepma, Sergio Ruiz Hernandez, Gernot Nehrke, Karline Soetaert, Albert Philipse, Bonny Kuipers, Mariette Wolthers

Research output: Contribution to conferenceAbstractAcademic


The impact of stoichiometry (raq = {Ca2+}:{CO32-}) on the new formation and subsequent growth of CaCO3 is important, as most natural waters and industrial crystallization processes proceed nonstoichiometrically. Therefore, we investigated in a broad range (10 -4 < raq < 104) the effect of solution stoichiometry at various, initially constant degrees of supersaturation (30 < Ωcal < 200; where Ω cal = {Ca2+}{CO32-}/Ksp), pH of 10.5 ± 0.27, and ambient temperature and pressure (Seepma et al., 2021). At raq = 1 and Ωcal < 150, dynamic light scattering (DLS) showed that ion adsorption onto nuclei (1 – 10 nm) was the dominant mechanism. At higher supersaturation levels, no continuum of particle sizes is observed with time, suggesting aggregation of prenucleation clusters into larger particles as dominant growth mechanism. At raq ≠ 1 (Ωcal = 100), prenucleation particles remained smaller than 10 nm for up to 15 hours. Cross-polarized light in optical light microscopy was used to measure the time needed for new particle formation and growth to at least 20 μm. This precipitation time depends strongly and asymmetrically on raq. Complementary Molecular Dynamics (MD) simulations confirm that raq affects CaCO3 nanoparticle formation substantially. At raq = 1 and Ωcal >> 1000, the largest nanoparticle in the system had a 21 - 68% larger gyration radius after 20 ns of simulation time than in non-stoichiometric systems. Our results imply that, besides Ωcal, stoichiometry affects particle size and persistence, growth and ripening time towards μm-sized crystals. Our results may help to improve understanding, prediction and formation of CaCO3 in geological, industrial and geo-engineering settings.
Original languageEnglish
Number of pages1
Publication statusPublished - 6 Jul 2021
EventGoldschmidt 2021 - virtual
Duration: 4 Jul 20219 Jul 2021


ConferenceGoldschmidt 2021


  • Solution stoichiometry
  • Crystallization
  • Scale formation
  • Dynamic light scattering
  • Crystal formation
  • calcium carbonate


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