The influence of pH and temperature on the rheology and stability of aqueous titanium dioxide dispersions

The effects of pH and temperature on the rheology and stability of aqueous dispersions of rutile (titanium dioxide) were investigated systematically. The dispersions exhibit shear-thinning behaviour, conforming to the Herschel-Bulkley or the Casson-type models in the shear rate range investigated. Extreme sensitivity with pH was observed, whereby the dispersion viscosity can be changed by as much as an order of magnitude with pH variation at constant volume fraction. The temperature effect study indicates that the relative contribution of Brownian motion and shear flow to the viscosity is dependent on the flocculation state of the dispersion. The rheological behaviour of the dispersions in this study has been explained in terms of hydrodynamic interactions between particles as well as non-hydrodynamic interactions. These observations have important implications in crossflow microfiltration of these dispersions. (C) 1997 Elsevier Science S.A.