Stabilization of PCC dispersions prepared directly in the mother-liquid after synthesis through the carbonation of (hydrated) lime

Various CaCO3-based products are often used in the form of concentrated aqueous dispersions. This study investigates the stabilization of PCC dispersions prepared directly in the mother-liquid after the carbonation of (hydrated) lime through the adsorption of a commercial sodium polyacrylate dispersant. The results demonstrate that the composition of the mother-liquid, particularly the Ca2+Ca2+ activity, profoundly influences virtually all processes pertinent to dispersion stabilization—from the initial charging of the CaCO3 surface in base PCC dispersions, to the surface charge regulation and dispersion stabilization efficiency of the polyacrylate dispersing agent. Rising prominence of the counterion condensation effects in Ca2+Ca2+ rich solutions limits the conditions conducive to the surface charge regulation through dispersant adsorption to an optimum pH range of about 8–11. Furthermore, dispersion stability analysis, based on the classical DLVO theory of colloid stability, and corroborated by experimental evidence in the form of particle size distribution analyses, also indicates that optimum stability conditions for such PCC dispersions are established with small dispersant doses (0.25–0.5% per dry weight) in the pH range of about 9–11.