Synthesis and characterization of spherical silica precipitated via emulsion route

The reaction of precipitation of amorphous silicon dioxide from aqueous solution of sodium silicate and hydrochloric acid in cyclohexane medium has been studied. The effects of experimental conditions on the dispersity and adsorptive character of the obtained silicas have been established on the basis of the particle size, polydispersity, specific surface area and pore characteristics. The effect of the dispersion–induction technique on the physicochemical characterization of the obtained silicas has been estimated. The application of homogenization has been found to lead to SiO2 particles of the most favourable dispersion and morphological character, while the application of a top propeller stirrer might be an alternative technique. The modification of the reaction involving precipitation of silica from sodium silicate emulsion dosed directly into hydrochloric acid has been shown to give SiO2 particles of a defined shape, provided that no exposure to ultrasound was employed. The silicas precipitated using a homogenizer and ultrasound bath have shown much higher specific surface area (ABET) than that of the obtained silica using the top propeller stirrer. The silica of the most favourable physicochemical parameters contained particles of the size of 400 nm, polydispersity of 0.005, and surface area of 466 m2/g.