Flocculation of precipitated calcium carbonate (PCC) by cationic tapioca starch with different charge densities. I: Experimental

The dynamics of the flocculation of precipitated calcium carbonate (PCC) with two commercial cationic tapioca starches (S858 and S880) with different charge densities were studied by small angle static light scattering. The effects of temperature, polymer dosage, ionic strength, and shear rate on the floc size and structure were investigated by employing a response surface methodology involving the central composite statistical design and analysis of variance (ANOVA). The evolution of floc size and structure was observed and it was found that larger and more compact flocs were produced by the high charge density starch S880. The flocʹs mass fractal dimension indicates the flocʹs compactness and it was found that the compactness increases as the flocculation proceeds. The ionic strength plays a significant role on the floc size with S880. Finally, the negative effect of shear rate on floc size was more pronounced for the low charge density starch S858.