Para-amino benzoic acid-mediated synthesis of vaterite phase of calcium carbonate

Calcium carbonate polymorphs were precipitated at room temperature and 80(a similar to)C by varying the precipitation pH, carbonate source, effect of solvent in presence and absence of structure directing agent such as para-aminobenzoic acid. Calcite phase of calcium carbonate was obtained when sodium hydrogen carbonate and/or sodium carbonate (used as precipitating agents) were added to calcium chloride solution at different pHs in water and/or methanol as solvent in separate experiments. Vaterite phase of calcium carbonate (CaCO3) has been synthesized by mixing calcium chloride and sodium carbonate in presence of para-aminobenzoic acid when water-methanol binary mixture was used as solvent. Vaterite phase of calcium carbonate crystallizes in P63/mmc, while that of calcite phase in R-3mc, respectively. Calcite phase of calcium carbonate exhibits rhombohedral morphology, while vaterite phase has spherical morphology.