Synthesis of peanut-like calcium carbonate intermediates in silica system containing partially hydrolyzed polyacrylamide and heavy alkyl-benzene sulfonate

- HPAM and HABS roughen the surfaces of CaCO3 particles.
- CaCO3 underwent morphological transformation from spherical to cubic-like shape.
- Peanut-like CaCO3 intermediates were obtained ascribe to package action of SiO2.

Calcium carbonate (CaCO3) crystals with various morphologies and polymorphs were synthesized from the aging calcium chloride (CaCl2) and sodium carbonate (Na2CO3) 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 CaCO3 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 CaCO3 particles occurred with increasing of aging time. All the CaCO3 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 SiO2-coated CaCO3 surfaces played a crucial role in modifying the crystals morphologies. A hypothetical mechanism for the formation process of the peanut-like CaCO3 was presented.

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