Zeta potential of anatase (TiO 2) in mixed solvents

Abstract

The replacement of water with mixed solvents (aqueous methanol and ethanol, up to 30% wt.) does not change the surface charge density dependence on the pH of anatase suspensions in 10 −3−10 −1 mol dm −3 KCI solutions. The negative ξ-potentials are decreased and the isoelectric point is shifted towards higher pH values in systems containing 10 −1 mol dm −3 KCl, LiCl, CsCl, or KI in 30% ethanol/water or 30% methanol/water mixtures as compared to pure aqueous systems. The effect is observed only at a sufficiently high ionic strength and alcohol concentration and is similar to that previously found for silica. The charge of anatase can be reversed by BaCl 2 and K 2SO 4 in aqueous and mixed solvent systems. Finally, analogous phenomena were observed with uniform yttria particles dispersed in ethanol/water mixtures in the presence of 10 −1 mol dm −3 KCl.