Anomalous transformation of calcite to vaterite: Significance of HEDTA on crystallization behavior and polymorphism at elevated temperatures

Phase transformation of calcite to vaterite in the presence of N-(2-hydroxy ethyl) ethylenediamine- N, N, N 1 - triacetic acid (HEDTA) is reported. The effect of HEDTA on the crystallization behavior and polymorphism of CaCO3 are studied at different temperatures (60 – 240 °C). The samples are characterized by powder X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscope and field emission scanning electron microscopy. The study reveals that above 170 °C, HEDTA facilitates the unusual transformation of calcite to vaterite, which could make it a possible potential scale inhibitor and also a boiler sludge conditioner at elevated temperatures. The present study also provides a novel understanding of the crystallization behavior of CaCO3 using HEDTA; conversion of a stable polymorph to a less stable one (calcite to vaterite), which can be extended to other systems by the careful optimization of different parameters.