Properties of Calcium Carbonate Prepared by Interfacial Reaction Method

Abstract

The hydrophobic powder of calcium carbonate (CaCO₃) was prepared by interfacial reaction method, in which one of the reactant was an emulsion consisting of aqueous solution of calcium chloride and benzene, and the other was aqueous solution of sodium carbonate, and the reaction had been made at surface of drops of liquid.
It was f ound by X-ray diffraction that the CaCO₃ powder was composed of two crystalline modifications, calcite and vaterite. And also, it was recognized that the fraction of calcite and vaterite was a little dependent on the emulsifying conditions.
It was found that the vaterite was transformed to calcite in water phase, as a function of time, and the reaction rates were 1.2%/hr at room temperature and 2.5%/hr at boiling water temperature respectively.
It was reco g nized that the kinetic data of the transition were applicable to Avrami's equation, one of the solid state models, and the slope of lines was 1.025.
These results suggest that the transition occurs in the solid phase. But, it could not be disregarded that the dissolution and deposition of CaCO₃ had played a significant part of the transition, because the transition actually took place in the presence of water.