Influence of polyvinylpyrrolidone on the precipitation of calcium carbonate and on the transformation of vaterite to calcite

The Precipitation process of calcium carbonate (CaCO3) in the absence and presence of poly (N-vinyl-2-pyrrolidone) (PVP) was investigated using scanning electron microscopy, powder X-ray diffraction, and Fourier transform infrared spectroscopy methods at room temperature. The results indicate that PVP does not affect the polymorphy, but has influence on their morphology and size of CaCO3 crystals. With the addition of PVP, the amorphous CaCO3 could aggregate into bigger amorphous spherulites before transforming to crystalline state. Also, the transformation from the thermodynamically unstable vaterite to the stable calcite was investigated in the presence of PVP. As a particle-stabilizing agent, PVP molecules inhibit the formation of vaterite, however, promote the formation of calcite as well as the rate of the solvent-mediated. transformation from vaterite to calcite. (C) 2003 Elsevier Science B.V. All rights reserved.