Effects of temperature on precipitation kinetics and microstructure of calcium carbonate in the presence of magnesium and sulphate ions

摘要

In the present work, the effects of the temperature on the kinetics and microstructure of CaCO_3, precipitated in the presence of magnesium and sulphate ions, were studied using degassing dissolved CO_2 method. The precipitates were identified by X-ray diffraction, atomic absorption spectroscopy and scanning electron microscopy. It was shown that at fixed temperature and ionic strength, the presence of sulphate and magnesium ions increased the induction time, decreased the crystal growth rate and reduced the amount of the CaCO_3 precipitates obtained. Magnesium induced the formation of aragonite form rather than the cal-cite and vaterite form. The increase of temperature in presence of magnesium and sulphate ions lead to a change on the effect of magnesium on kinetics of CaCO_3 precipitation and caused the Mg~(2+) ions incorporation in the CaCO_3 lattice. The increase of temperature favoured the aragonite phase in magnesium solutions and both aragonite and vaterite in presence of sulphate ions.