Influence of Ion Size on Short-Range Repulsive Forces between Silica Surfaces

Abstract

The influence of counterion size on short-range repulsive forces at high salt concentrations was investigated with silica slurries at various pHs. Ions from the lyotropic series of monovalent electrolytes (LiCl, NaCl, KCl, and CsCl) were used to coagulate dispersed slurries. Measurements of viscosity and sedimentation rate were performed. The results at high salt concentrations and volume fractions of silica clearly show that the extent of the short-range repulsive forces correlates with the size of the unhydrated ion. This trend is opposite to the ion-adsorption sequence on silica at low volume fractions of solids or lower ionic strength. Our results are also contrary to the widely accepted hydration force model but concur with the recently developed reference-hypernetted chain statistical mechanics models describing the interaction of ions with solvated surfaces.

Adhesion between Silica Particle and Mica Surfaces in Water and Electrolyte Solutions

“…The adhesion dependence on the cation species is correlated excellently with the recent rheological studies performed with silica and aluminum slurries by Colic, and Franks and co-authors (4)(5)(6)(7)(8). They have shown that the strength of attractive particle networks in the high electrolyte concentration solutions decreases in the sequence: Li + > Na + > K + > Cs + .…”

Dynamic Features of Short-Range Interaction Force and Adhesion in Solutions

“…There are the other reports claiming that the repulsive force between silica surfaces is explained by the hydration of surfaces rather than by a gel layer (8,9). The existence of a thick structured layer is also suggested by coagulation experiments with silica dispersions (24) and rheological studies on silica and aluminum slurries (25)(26)(27).…”

Origins of the Non-DLVO Force between Glass Surfaces in Aqueous Solution

“…However, in silica and glass systems the additional force does not seem to be strongly dependent on the type or concentration of electrolyte. In fact, a decrease in magnitude of the non-DLVO forces with increasing electrolyte concentration has been reported (2,3,21). As a result of these investigations, it is generally assumed that the origin of the non-DLVO forces on silica is different than those in other oxide systems.…”