Preparation of colloidal silica using peptization method

Colloidal silica was prepared by peptizing a hydro-wet gel obtained with sodiumsilicate solution in a mixture with nitric acid and pure water. Prepared samples exhibited a fairly uniform particle size of ca. 20 nm and could be concentrated up to over 20 wt% SiO2 by ultrafiltration. Various parameters influencing the peptization efficiency and the particle property were investigated. The characteristics of the prepared colloidal silica were examined by TEM, TGA, and FT-IR spectroscopy. The peptization efficiency turns out to be mainly dependent upon the gelling conditions such as the concentration of silica source, the gelling pH, and the aging time. In addition, hydrothermal treatment is found to reduce the density of external silanol groups and thus make the colloidal silica stabilized.