Naslov
Effects of heat treatment on the aggregation and charging of Stöber-type silica

Autori
Kobayashi, Motoyoshi ; Skarba, Michal ; Galletto, Paolo ; Čakara, Duško ; Borkovec, Michal*

Izvornik
Journal of colloid and interface science (0021-9797) 292 (2005), 1; 139-147

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
Aggregation ; Coagulation ; Colloid stability ; Silica ; Heat treatment ; DLVO theory
(Aggregation ; Coagulation ; Colloid stability ; Silica ; Heat treatment ; DLVO theoryeatment DLVO theory)

Sažetak
Colloidal silica is known to be stable at high salt concentrations and low pH, where silica is basically uncharged. This observation is in qualitative disagreement with the theory of Derjaguin, Landau, Verwey, and Overbeek (DLVO), which predicts rapid aggregation (or coagulation) under these conditions. This study reports a very different behaviour for Stöber-type silica heated at 800 °C, as these particles follow DLVO theory quantitatively. Unheated samples behave approximatively according to DLVO theory, but they show systematic deviations, in particular, featuring higher stability at low pH. The heat treatment also substantially modifies the charging properties, as heated particles show titratable surface charge densities in the range expected for the water–silica interface, while much higher charge densities are observed for the unheated samples. The electrophoretic mobilities, on the other hand, are hardly influenced by the heat treatment. We suspect that the suspension stability of the unheated particles is influenced by the presence of a hairy-layer of polysilicilic acid chains on the surface.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

POVEZANOST RADA