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HWAHAK KONGHAK,
Vol.36, No.2, 262-266, 1998
Vol.36, No.2, 262-266, 1998
NH4Cl 존재하에서 탄산가스반응법에 의한 구헝 Vaterite 합성
The Preparation of Spherical Vaterite in the Presence of NH4Cl by Carbonation Process
수산화 칼슘 수용액에 NH4Cl을 첨가하여 탄산가스 반응법으로 탄산칼슘을 합성하였다. 반응시간, 반응온도, NH4Cl의 양 그리고 pH에 따른 탄산칼슘 결정형태에 미치는 영향을 연구하였는데, 반응시간에 따라서 탄산칼슘 결정형태에는 많은 영향이 있음을 알 수 있었다. 즉, 2.5wt%의 NH4Cl용액에 Ca(OH)2를 용해하여 반응온도 20℃에서 탄산가스반응법으로 입자를 합성시, 반응초기에는 구형의 vaterite가 합성되었으나, 반응시간이 30분을 경과하면 vaterite에서 안정한 calcite로 전환됨을 관찰하였다. 그리고 용액의 pH에도 많은 영향이 있었으나, 반응온도에는 영향이 거의 없었다. 따라서 구형의 vaterite를 합성하는 최적조건으로서 반응온도 20℃, 반응시간 10분 그리고 NH4Cl의 양은 5.0wt%/H2O에서 pH의 범위는 9.9-10.5이었다.
Calcium carbonate was precipitated by carbonation in the aqueous solution of Ca(OH)2 and NH4Cl as additive. The effect of reaction time, reaction temperature, concentrations of NH4Cl and pH on the particle shape and polymorphs of calcium carbonate was investigated. The reaction time were found to have a significant effect on the shape and polymorphs of calcium carbonate. In these reaction conditions such as 2.5 wt% NH4Cl at 20℃, the early stage of reaction, the precipitated calcium carbonate was vaterite, but after 30 minutes, vaterite was transformed to calcite. And pH has effect on the polymorphs, but reaction temperature has no effect on the polymorphs. From these results, we found that spherical vaterites were prepared in the presence of 5 wt%/H2O NH4Cl solution for 10 mins at 20℃ and pH range was 9.9-10.5.
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