Crystal Research and Technology
Cryst. Res. Technol. 40, 586 (2005) - Abstract -

Effect of monovalent salts on morphology of calcium carbonate crystallized in Couette-Taylor reactor

Taesung Jung, Woo-Sik Kim*, and Chang Kyun Choi

School of Chemical Engineering, Seoul National University, Seoul 151-744, Korea
*School of Chemical Engineering, KRRC, Kyunghee University, Yongin, Kyungki-Do 449-701, Korea

Keywords monovalent salt, morphology, agglomeration, calcium carbonate, crystallization, Couette-Taylor reactor
PACS 81.10.-h
DOI 10.1002/crat.200410387

Monovalent ionic additives, Na+, K+ and NH4+ impact on the morphology and agglomeration of CaCO3 crystals. As increasing the additive concentration, the regular shaped crystals such as rhombohedron and spindle are changed to irregular one due to the inclusion of Na+ and K+ into the crystal structure. The inclusion of Na+ and K+ is detected using ICP-AES. The partition of coefficients of Na+ and K+ are estimated as 9.74x10-4, 9.73x10-4, respectively and the amount of inclusion in the crystals is about 2x103 ppm. However, the inclusion of ions does not modify a crystal structure of calcite. Since NH4+ is large in radius, it is not included in crystal but shifts the spindle shape of crystal to the rhombohedral one. It is interesting to find that such modification of crystal morphology begins to appear at high additive concentration (0.05 M). In addition, the crystal agglomeration is promoted because the electric repulsive charge is reduced as increasing the additive concentration.




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