Mixed Colloidal Dispersions of Silica and Hematite

Abstract

The colloidal behavior of mixed dispersions containing hematite (diameter=138.9 nm) and silica (diameter=7.0 nm) has been studied by measuring the stability ratio, zeta potential, and particle size. When various particle numbers of silica were added to a constant particle number of hematite, different colloidal behavior was observed, depending on the pH. In a pH region where the two solids were oppositely charged, hematite particles showed a dispersion-coagulation-redispersion process with increasing particle number of silica, resulting in a coating layer of silica particles on the hematite surface. On the other hand, in a region where both solids were negative, the addition of silica enhanced the stability of the hematite.