| Synthesis of Precipitated Calcium carbonate in Ca(OH)2-CO2-H2O System by the Continuous Drop Method of Ca(OH)2 Slurry |
| Ji-Whan Ahn, Jae-Sung Lee1, Sung-Min Joo, Hyung-Seok Kim, Jong-Kuk Kim2, Choon Han1, Hwan Kim3 |
Korea Institute of Geoscience & Mineral Resources
1Department of Chemical Engineering,Kwangwoon University
2Institute of Basic Science, Changwon National University
3School of Materials Science and Engineering, Seoul National University |
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| ABSTRACT |
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Experiments were conducted to investigate the synthesis characteristics of Precipitated Calcium Carbonate(for short PCC) in Ca(OH)$_2-CO_2-H_2O$ system by the continuous drop method of Ca(OH)$_2$ slurry into the solution containing $CO_2$(aq). When the flow rate of $CO_2$(g) increases and the concentration of Ca(OH)$_2$ slurry become low, the absorption rate of $CO_2$(g) become faster than the dissolution rate of Ca(OH)$_2$. Consequently, the growth of the calcite crystal plane is facilitated resulting in synthesis of $1.0{mu}m$ of rhombohedral calcite. On the other hand, when the flow rate of $CO_2$(g) decreases and the concentration of Ca(OH)$_2-CO_2-H_2O$ slurry become high, new nuclei is created along with the crystal growth resulting in synthesis of $0.1{mu}m$ of prismatic calcite. Maintaining 1.0wt% of Ca(OH)$_2-CO_2-H_2O$ slurry, 120 drops/min of drop rate and $25^{circ}C$ of temperature, the shape of PCC shows colloidal and spherical agglomerate at 100 mL/min of the flow rate of $CO_2$(g); the mixture of rhombohedral and plate-shaped calcite, at 200∼500 mL/min. Therefore, as the flow rate of $CO_2$(g) increases, the shape of PCC changes from colloidal and rhombohedral calcite to plate-shaped calcite. Maintaining 500 mL/min of the flow rate of $CO_2$(g), 120 drops/min of the drop rate of Ca(OH)$_2$ slurry, and $25^{circ}C$ of temperature, the shape of PCC shows the plate-shaped calcite at 1.0∼3.0 wt% of Ca(OH)$_2$ slurry; the hexagonal plate-shape calcite of the thickness of $0.1{mu}m$ and the width of $1.0{mu}m$, at 4.0 wt%. |
| Key words:
PCC, Continuous drop method, Calcite, Ca(OH)$_2-CO_2-H_2O$ |
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