High-yield synthesis of vaterite CaCO3 microspheres in ethanol/water: structural characterization and formation mechanisms

Abstract

Calcium carbonate (CaCO 3 ) is widely used as an important model system for investigating inorganic precipitation reaction or crystallization. However, recent results show that the yield of vaterite CaCO 3 microspheres is poor in ethanol/water in the presence of polyelectrolyte poly(sodium 4-styrenesulfate) (PSS), which is up to 16 mM. We now report on an approach to synthesize pure vaterite CaCO 3 microspheres through improving the concentration of polymer PSS and the yield is greatly high up to 80 mM. The exploration provides the possibility for large-scale synthesis of CaCO 3 materials with controllable morphology and crystallographic structure in aqueous solution at room temperature. The possible formation mechanism toward the occurrence of vaterite CaCO 3 microspheres has also been illustrated in virtue of a series of time-resolved experimental results. It is revealed that the vaterite microspheres evolve gradually from the initial amorphous precursor, to poorly crystallized nanoparticles, to sphere-like aggregates, and then to vaterite microspheres embedded with the calcite rhombohedra, finally to the vaterite microspheres with smooth surface. This research may provide a new viewpoint into the forming process of vaterite CaCO 3 microspheres.

Synthesis of calcium carbonate in trace water environments

“…[26][27][28] In addition, Anhydrous calcium chloride and ammonium carbonate were dissolved in absolute ethanol, and then the solutions were added to absolute ethanol, or other alcohols, using syringe pumps under continuous magnetic stirring until the desired concentration was reached (see the Experimental section in the ESI †).…”

Nucleation and Growth of Mg-Calcite Spherulites Induced by the BacteriumCurvibacter lanceolatusStrain HJ-1

“…The nucleation and growth of calcite spherulites is closely associated with the ambient microenvironment, such as the activities and types of bacteria present, alkalinity, ion species, additives, and impurities (Beck & Andreassen, 2010 a ). The influence of various factors on the precipitation of calcite spherulites has been investigated by many authors (Zhang et al, 2015; Xu et al, 2017), and spherulitic precipitation appears to be extremely complex since virtually any parameter may trigger morphological change. Despite nearly a century of research on the growth features of such crystals (Goldenfeld, 1987; Gránásy et al, 2005; Beck & Andreassen 2010a, 2010b), the formation of spherulites remains poorly understood.…”

Exploring the Influence of Reaction Parameters on the Preparation of Calcium Carbonate by Spontaneous Precipitation

“…Citrate ions also can play a role in initiating the nucleation of vaterite in this stage through a slow crystallization process . In the growth stage of CaCO 3 , the citrate ions further adsorb on the surface of the as‐formed composite and prevent the further growth of particles along specific planes, which leads to spherical morphology . Citrate ions preferentially adsorb on the vaterite nuclei, they can prevent the vaterite transform into calcite during the growth process.…”

“…Spontaneous precipitation by the mixing of two concentrated solutions of calcium and carbonate results in a gelatinous matter when ionic activity product exceeds the solubility product (KSP) of amorphous calcium carbonate. This amorphous precursor is highly unstable and will transform into a mixture of the crystalline polymorphs within few minutes if kept in solution . In this work, calcium carbonate crystals were synthesized by spontaneous precipitation in the presence of trisodium citrate and NaOH.…”