EFFECTS OF SURFACTANTS ON CACO3 SPHERES PREPARED BY INTERFACIAL REACTION METHOD

Spherical particles of CaCO3 powder were prepared by an interfacial reaction method in which CaCO3 powder was formed by the reaction of K2CO3 aqueous solution emulsified in benzene with CaCl2 aqueous solution. The spherical particles were prepared under the following conditions; concentration of K2CO3 was 3 mol/liter and concentration of CaCl2 was 0.2 mol/liter. Five nonionic surface active agents in the form of sorbitan esters of fatty acids were used in the concentration range of 0.01-1.0 wt%, for examining the effects of the surfactants on the spherical particle content and vaterite fraction. The spherical particle content and the vaterite fraction were determined by X-ray diffraction and microphotographic methods, respectively. It was found that the spherical particle content depended on the vaterite fraction, and that the vaterite fraction was related to the concentration and HLB-number of the surfactant. These results suggest that the vaterite sphere is initially formed by the interfacial reaction in 100% yield. After that, the vaterite partially transforms into calcite while in contact with the water phase. It is concluded that differences in the vaterite fraction are caused by the conditions of contacting with water, which depend on the adsorption of surfactants on the surface of the spheres. © 1979.