Dispersion of Silica Fines in Water-Ethanol Suspensions
Original entry by Hyerim Hwang, AP 225, Fall 2011.
J. Ren, S. Song, A. Lopez-Valdinieso, J. Shen, and S. Lu, "Dispersion of Silica Fines in Water-Ethanol Suspensions", Journal of Colloid and interface Science 2001 238, 279-284
- Dispersion of silica
As shown in Figure 1, the settling efficiency increased with increasing settling time. The silica fines exhibit different degrees of dispersion in different liquid media. The strongest dispersion occurs in the water-ethanol suspension, while the weakest is observed in the aqueous. suspension. The results from Figure 2 shows that the different interactions between the silica particles and the liquid media leads silica fines to have different dispersion behavior in different liquids. Plus, Figure 3 shows that the wetting rate increased as the fraction increased, whereas the negative zeta potentials of silica fines steadily decreased when the fraction increased, which means that there is no correlation between zeta potentials and the dispersion of silica fines.
- Solvation film thickness on silica
A formula has been presented to determine the thickness of the solvation film on the basis of Einstein's theory of viscosity of dispersions, from which the solvation film thickness on silica particles in various liquid mediums have been estimated through the measurement of the suspension viscosity as a function of the volume fraction of the particles.
The results from this paper demonstrates that the dispersion stability of the silica suspensions increased as the fraction of ethanol increased. The stability was stronger in a pure ethanol suspension than in a pure water suspension and it means that stability which is correlated with the lyophilicity of the particles is predominated by the DLVO theory but not by surface charge.