Effect of sodium stearate and calcium ion on dispersion properties of precipitated calcium carbonate suspensions

The adsorptions of sodium stearate and calcium ion on calcium carbonate particles in aqueous media were investigated in terms of zeta potential and yield stress. The zeta potentials of calcium carbonate particles were fluctuated strongly by the co-adsorption of stearate molecules and calcium ions, showing the counter effect on the potential change. At the high concentration of stearate, zeta potentials varied with the surface state of adsorbed surfactant layer. The co-adsorption of stearate and calcium ion indicated a strong interaction of calcium ion with solid/liquid interface at low concentrations, however, showed a similar trend with the case of stearate at high concentrations. Since the zeta potential presents the potential at shear plane, practically it is responsible for the interaction of particles and the destabilization of solution structure at yield stress (τ0). The yield stresses of suspensions determined by Casson’s plots were postulated to present the persistency of stagnant bulk state of dispersions near zero shear rate and inverse to the square of zeta potential. Further, the stability of calcium carbonate suspension mainly depends on an electrostatic repulsion force given by the classical DLVO theory.