LAUSR

Abstract Calcium carbonate (CaCO 3 ) crystals with various morphologies and polymorphs were synthesized from the aging calcium chloride (CaCl 2 ) and sodium carbonate (Na 2 CO 3 ) solution using inorganic silica as well as organic partially hydrolyzed polyacrylamide (HPAM) and surfactant heavy alkyl-benzene sulfonate (HABS) as effective crystal growth modifiers by the rapidly mixing method at 45 °C. The effect of different additives on controlling calcium carbonate morphology has been investigated by field emission scanning electron microscopy (FESEM), fourier transform infrared (FT-IR) spectrometer and X-ray diffraction (XRD). Peanut-like CaCO 3 particles were successfully obtained after the mixture system being aged for 6 h at pH of 11.3 ± 0.2, and the transition from sphere through peanut-like shape to cubic shape for CaCO 3 particles occurred with increasing of aging time. All the CaCO 3 particles were pure calcite when pH was unadjusted (pH = 11.2 ± 0.1), however, lower pH favored the formation of vaterite. The research results showed that the adsorption of HPAM and HABS on SiO 2 -coated CaCO 3 surfaces played a crucial role in modifying the crystals morphologies. A hypothetical mechanism for the formation process of the peanut-like CaCO 3 was presented.