Abstrakt

Calcium carbonate is a widespread compound in nature and it can be produced by living organisms in the biomineralization process. Calcite, aragonite and vaterite are anhydrous polymorphic forms of calcium carbonate, wherein the calcite is the most thermodynamically stable. Vaterite is the metastable crystalline phase, which can be a precursor of calcite and aragonite, because it can easily transformed by dissolution and re crystallization into more stable forms. Synthetic CaCO3 obtained in the precipitation process is used as an additive in many products. There are two main methods for the production of precipitated calcium carbonate (PCC) on the industrial scale, i.e. precipitation in the gas liquid system and in the liquid liquid system. Diverse PCC applications require the use of well defined particles which are characterized by the polymorph composition, the particle morphology and the crystal size distribution. The concentration of reagents, temperature, pH, duration of the reaction and the presence of inorganic and organic additives play an important role during the calcium carbonate formation and influence on the product characteristics. The effect of glucose, fructose, sucrose and trehalose on the precipitation of CaCO3 in the gas liquid system has been investigated and it has been shown that the addition of saccharides into the reaction mixture can influence the polymorph composition of produced precipitates. Saccharides are characterized by different pKa values. The lower the pKa of the saccharide, the lower the initial pH of the aqueous solution. As a consequence, it leads to a longer initial time of reaction. The presence of saccharides in the solution increases the rate of the CO2 absorption. In addition, mono- and disaccharides are able to stabilize the pre-nucleation clusters of CaCO3, i.e. prevent their aggregation and coalescence. In this work, the interaction of selected saccharides has been studied using the NP-HPLC technique. As a stationary phase vaterite and rhombohedral calcite were used, while DMSO was an eluent. Solutions of saccharides in DMSO were samples injected to the tested columns. Among the analyzed disaccharides, trehalose is characterized by the smallest capacity factor for both calcium carbonate polymorphs, thus, it exhibits the weakest adsorptive interactions. Comparing monosaccharides, fructose interacts stronger with vaterite, while higher adsorptive interactions with calcite has been observed for glucose.

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