Correlation between the zeta potential and rheological properties of anatase dispersions

The viscosity at an arbitrarily selected shear rate of 1.16 s(-1) and the y ield stress of anatase dispersions are linearly correlated, and both show a maximum at the isoelectric point (IEP) at pristine conditions. The rheolog ical properties of anatase dispersions respond; to the shift in the IEP to higher pH values, which is observed in concentrated solutions of 1-1 electr olytes and in the presence of the organic cosolvents, but the shift in the pH corresponding to a maximum viscosity does not exactly match the shift in the IEP. In contrast with the electrokinetic curves, the rheological curve s at high ionic strengths are rather insensitive to the nature of the suppo rting electrolyte. The acidic branch of the viscosity(pH) curves is relativ ely insensitive to the ionic strength while the slope of the basic branch d ecreases when the ionic strength increases. (C) 1999 Academic Press.