Industries use displacement washing with solvent to separate solutes from the voids in a porous medium. Tarleton, Wakeman, and Liang (Trans IchemE, 2003) developed a new technique to improve separation of solid-liquid mixture, using an electric field during washing. They recorded zeta potential of titania (TiO2) in 0.01 or 0.001 M concentrations of NaNO3 solutions at different pH levels. The data from their experiments are listed in table at the right. The zeta potential is the overall charge a particle acquires in a specific medium. It is used to understand and control colloidal suspensions, emulsions, and slurries. Its value is related to the stability of colloidal dispersions. Colloids with high zeta potential (negative or positive) are electrically stabilized. Colloids with low zeta potentials tend to coagulate or flocculate.
a Make a scatterplot of zeta potential against the solution pH for each NaNO3 concentration.
b Describe the nature of the relationships.
c Fit the appropriate model to describe the predicted zeta potential.