Abstract
As well as the variation of particle size, the polymorphism of calcium carbonate was investigated using an anionic micelle system in a standard mixing reactor. Anionic surfactants of SDS (sodium dodecyl sulfate) and AOT (sodium bis (2-ethylhexyl) sulfosuccinate) were used to stabilize the aqueous reactant solutions for the reaction crystallization in continuous phase of cyclohexane (water in oil microemulsion system). As fractions of the surfactant and cyclohexane in the microemulsion gradually increased, the structural transformation of calcium carbonate from calcite to vaterite suddenly occurred. The polymorphic ratio of vaterite over calcite, Xv, could allow evaluating the homogeneity and completeness of micellization in each operating condition. The impact of SDS micelle on the morphological transformation was clearer than AOT. Based on the concurrent fluctuation of size and morphology in AOT reverse micelle, the phase discrepancy region of R (= [H2O]/ [surfactant]) was also confirmed in the crystallization of calcium carbonate experimentally.
