Electrostatic stabilization of ultrafine titania in ethanol

The colloidal stability of a suspension of very fine titania (TiO2) powder in ethanol has been investigated. The electro-kinetic behavior and stability ratios were determined as a function of operational pH and salt concentration. We show that the stability is strongly dependent on ionic strength; the TiO2 suspensions will aggregate relatively rapidly at ionic strengths > 10(-3)M, while suspensions exhibiting long-term stability can be made at less than or equal to10(-4)M, providing that the zeta potential of the TiO2 particles is sufficiently high, i.e., \xi\ = 40-50 mV. Theoretical estimates of the stability based on electrostatic repulsion show a relatively good correlation with the experimental results, in particular in the acidic operational pH (pH*) range.