engleski

Morphological kinetics in calcium carbonate precipitation

Precipitated calcium carbonate (PCC) is receiving a large attention in industry as a specialty product. Different process conditions are used, producing crystals of different shapes. The monitoring of crystal population kinetics is usually made by laser diffraction, but the size distributions are obtained in volume and are not easy to interpret due to difficulties in the calculation of correct shape factors. Morphology can be investigated by particle imageing. It was therefore decided to use image analysis to characterize quantitatively the shapes observed during the precipitation of ultrapure calcium carbonate in a water solution of calcium nitrate and monoethanolamine (MEA) in a well-stirred contactor with and without an additive (sucrose). Crystals were observed by SEM, and digital images were directly captured and analyzed. Crystals were also examined by laser diffraction, IR-spectroscopy, and XRD. Sample specific surfaces were obtained by BET method. Based on these results crystal phase transformations and morphological kinetics during precipitation are discussed.

precipitated calcium carbonate; phase transformation; image analysis

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