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TEM Characterization of Precipitated Calcium Carbonate Prepared by Bubbling Method

In this work, the effect of different parameters on the particle morphology and size of produced PCC was studied. Calcium carbonate was precipitated by bubbling 20% CO_2/80% N_2 gas mixture through an aqueous suspension of Ca(OH)_2. Constant driving force, i.e., constant supersaturation, was maintained by PID regulation of electrical conductivity. The experiments were carried out at temperature 20 - 50 &ordm ; C, electrical conductivity 1 - 7 mS cm^-1, flow rate of gas mixture 1 - 5 dm^3 min^-1, stirring speed 800 - 1400 rpm and mass concentration of Ca(OH)_2 suspension 50 - 150 g dm^-3. The samples of precipitates were characterized by FT-IR spectroscopy, TEM and BET analysis. At the examined range of experimental conditions calcite was the only polymorph that precipitated. It was found that temperature and supersaturation have significante influence on both, morphology and size of the produced PCC. Thus, the size of crystal varied in the range from app. 30 nm - 1.5 um having various morphologies: rhombohedral, truncated prismatic, scalenohedral, chain-like and spheroidal.

precipitated calcium carbonate; carbonation; TEM

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