Effect of surfactants on the size and morphology of the silica particles prepared by an emulsion technique

Studies were performed on precipitation of silica in an emulsion system from aqueous solution of sodium metasilicate and hydrochloric acid. Cyclohexane formed the organic phase. Anionic, cationic and non-ionic surfactants were used as emulsifiers. Optimum composition of the emulsion and optimum parameters for the precipitation reaction were established. Effects of a dispersing medium on quality of the produced silicas were examined. The silicas were subjected to physicochemical characterization. Bulk density, water, dibutyl phthalate and paraffin oil absorbing capacities were measured. Surface charge of the obtained dispersion, particle size and shape of the formed silicas were estimated. Specific surface area (BET) was defined and the complete pore characteristics was also presented for the selected silicas. Application of Rokanol K-7 (C16-22O(CH2CH2O)(7)H) as an emulsifier resulted in production of almost ideally spherical silica particles of nanometric size and of a monodisperse character. (C) 2002 Kluwer Academic Publishers.