A unified analysis of the coagulation behaviour of silica hydrosols—when the colloid and polymer science meet

Abstract

An allegedly anomalous behaviour of aqueous dispersions of silica has attracted continually a great attention from Thomas Graham’s time. However, even recent coagulation experiments with apparently well-defined colloidal silica spheres are not interpretable when their surface is assumed intact in contact with water. In fact, various explanations such as a hairy layer of polysilicic acid and the hydration layer on the silica surface are well-known but not proven accompaniments of the hydration process. It has been previously suggested (Skvarla, J., Langmuir, 29:8809–8824, 2013) basing on a combination of the soft-sphere model of colloids, surface charge data, and the Flory-Donnan theory that a swellable polyelectrolyte gel-like layer develops inherently on the surface of highly charged silica in aquoeus KCl solutions. Here, we support this rationalization by extending the coagulation analysis. Results are also discussed from the standpoint of approaches associated with the traditional and extended DLVO theories.