Fine silica powders were synthesized from sodium silicate at room temperature using w/o emulsion containing water, nonionic surfactant of Triton N-57, and cyclohexane. Submicron and sodium-free silica particles could be prepared at low cost using inexpensive starting material of aqueous sodium silicate solution and ion exchange of ammonium sulfate. The particle size and size distribution of the silica powders were affected by the factors of reaction time, and concentrations of surfactant and sodium silicate solutions. The particle size of silica powders could be controlled by the same factors to be ranged from submicron to micron sizes. The particle Size of SiO2 decreased with reaction time and concentration of surfactant, but increased with concentration of sodium silicate. The preparation conditions were experimentally determined for obtaining the silica powder with submicrori size, narrow size distribution, sphere in shape, and high purity without sodium contamination. (c) 2006 Elsevier B.V. All rights reserved.