Zeta potentials of monodispersed, spherical silica particles in mixed solvents as a function of cesium chloride concentration

Zeta potentials of silica are negative in most mixed solvents (99% organic co-solvent, 1% water), but in t-butanol and pyridine they are positive. Whe n CsCI is added to the suspension as a probe substance, two types of behavi or are observed. In solvents of epsilon > 25, the xi potential asymptotical ly approaches zero, while in solvents of lower dielectric constant, the sig n of xi potential is reversed to positive at a sufficiently high CsCI conce ntration, c(rev). In order to evaluate the nature of interaction leading to different solvent responses, a range of frequently used solvent scales rel ating to specific interactions between the components of the system were co mpared. A moderate correlation was found between c(rev) for silica and one solvent property alone, and those previously found for anatase, respectivel y. Using linear combinations of two solvent scales improved the correlation , but it was still not satisfactory. However, considering separately the co ntributions from both solvent components, a nearly statistically significan t correlation was found. The results are evaluated considering the particul ar behaviour of each solvent group, and the specific influence of the mater ial properties of silica and of possible impurities present in the system. (C) 2000 Elsevier Science B.V. All rights reserved.