Study On The Dispersion Of Nano-sized CaCO₃ In The Aqueous System And Its Mechanism

In order to realize the application of nano-sized CaCO₃ in the textile field, an aqueous dispersion of nano-sized CaCO₃ was prepared through adding dispersant and ultrasonic processing in this paper. The mechanism of the dispersion of nano-sized CaCO₃ in aqueous system was discussed comprehensively and deeply and the dispersive condition for a better dispersion was determined, which would contribute the application of nano-sized CaCO₃ in aqueous materials.Primarily SPP, SHMP, SDBS, CTAB, PEG400, Tween 80, OP-10 and PAANa was selected to work as the dispersants. Through measuring the particle size of nano-sized CaCO₃ and the stability of dispersion, SDBS was thought to be the most suitable dispersant for the dispersion of nano-sized CaCO₃ in aqueous system among the above eight dispersants.In order to get a better understanding of the mechanism of the dispersion of nano-sized CaCO₃ in aqueous system, the adsorption amount of SDBS on nano-sized CaCO₃ in aqueous system, the zeta potential change and the stability of adsorption were measured. The results showed that SDBS could be adsorbed on nano-sized CaCO₃, and the adsorption amount of SDBS on nano-sized CaCO₃ became larger with the increasing concentration of SDBS solution and reached saturated adsorption when the concentration exceeded 2g/L. pH had an impact on the adsorption amount, and the amount of adsorption became smaller with the increase of pH. After SDBS was adsorbed on nano-sized CaCO₃, the change of zeta potential was great. The adsorption of SDBS on nano-sized CaCO₃ was a spontaneous process and this adsorption was relatively stableThe particle size of nano-sized CaCO₃ and the stability of dispersions, which were prepared by different ultrasonic processing method or with different ultrasonic processing time, SDBS amount and pH, were measured. Combined with the adsorption of SDBS on nano-sized CaCO₃, the mechanism of the dispersion of nano-sized CaCO₃ in aqueous system was discussed by employing the extended DLVO theory and the dispersive condition for a better dispersion was determined. The results showed that SDBS could improve the dispersion and stability of nano-sized CaCO₃ in aqueous system by enhancing the electrostatic repulsion and steric hindrance between particles and the hydratation film. A stable aqueous dispersion of nano-sized CaCO₃ could be achieved when the amount of SDBS was between 0.5g/L～2g/L, pH was at 9 and the ultrasonic processing time was 10 min.Aimed at the problem that metal ions in the modified system could destruct the stability of dispersion, KCl, MgCl₂ and AlCl₃ was added into the prepared aqueous dispersion of nano-sized CaCO₃ respectively, the influence of metal ions on the stability of dispersion was observed. The results showed that when adding KCl, MgCl₂ and AlCl₃ into the aqueous dispersion of nano-sized CaCO₃ respectively, the stability of dispersion could be disturbed and the stability decreased with the increasing concentration of metal ions. The impact of the metal ions on the stability of dispersions at different pH was same, when the dispersions had same concentration of SDBS solution. In the same condition, the ability of different metal ion to destroy the stability was different, and the ability ranked in the following order, Al³⁺>Mg²⁺>>K⁺. When the amount of SDBS increased, the destructive power of K⁺ became stronger, while the destructive power of Mg²⁺ and Al³⁺ weakened. So when preparing the aqueous dispersion of nano-sized CaCO₃, the amount of SDBS should be determined according the final condition in which the dispersion was applied.