Synergistic Effect of EDTA and HEDP on the Crystal Growth, Polymorphism, and Morphology of CaCO3

Polymorphic compositions of CaCO3 synthesized under the influence of a blended system of EDTA and HEDP between 60 and 230 degrees C using a controlled precipitation technique from CaCl2 solution using Na2CO3 has been investigated. The phases and structures of the samples were characterized by Raman, FTIR, and powder XRD techniques. The morphological studies were carried out using SEM, field emission scanning electron microscope (FESEM), and TEM. Usually, at higher temperatures vaterite and aragonite are transformed into stable calcite. Here, we report the stabilization of metastable aragonite and vaterite in the presence of a blended system of EDTA and HEDP at 200 and 230 degrees C. We also report a novel morphology, roselike structure for vaterite at 230 degrees C, which is not reported earlier.