engleski

Synthesis of calcite crystals with well developed (001) faces

Calcium carbonate crystals with different morphologies are interesting model for studying the additive-controlled processes which are important for pharmaceutical industry and for understanding the crystallization in biological systems [1]. Calcite is the most stable calcium carbonate polymorph that crystallizes with notable variety of habits under different environmental conditions. The addition of inorganic ions such as Mg2+ and Li+ can exert profound effect on the calcite morphology [2]. In previous experimental studies it has been shown that increasing amounts of lithium enhance the formation of (001) calcite form [3]. Atomistic simulation of predicted calcite morphology shows that the crystals, with incorporated lithium ions are tabular, comprising basal (001) and (104) side faces [4]. Such crystals could be used as a good model for determination of adsorption mechanisms of organic molecules on the (001) calcite surface. The aim of this study was to define the factors that favor the formation of plate-like calcite in a number of model systems. For this purpose the hydrodynamic parameters (a mode of mixing of the reaction components) and the concentration of the lithium ions, in the range from, c = 0.0 to 1.0 mol dm−3, were extensively studied. Precipitated calcite samples were studied by FTIR/ATR spectroscopy, thermogravimetry and PXRD method. The SEM and AFM microscopy were used for identification and surface analysis of (001) face. In addition, the chemical composition of the precipitate has been determined by the ion chromatography. The results indicated that the plate-like calcite is preferably precipitated when the ultrasound was applied, as well as after the addition of lithium ions at concentrations higher than, c = 0.3 mol dm−3. Precipitation of the plate-like calcite is also observed in the systems in which the magnetic and mechanical stirring and higher concentrations of lithium ions in the solution were applied.

calcium carbonate ; lithium ; plate-like calcite

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