Preparation of Stable Colloidal Silica with Controlled Size Nano Spheres from Sodium Silicate Solution

The formation process of stable colloidal silica solution was discussed in this article. The affecting parameter including pH, zeta potential, and colloidal concentration was investigated to elucidate the stability of colloid. Sodium silicate was used as the silica source. The colloidal silica prepared via sol-gel method at the base condition. Sodium ion of sodium silicate was removed by ion-exchanging to obtain the active silicic acid which was titrated with potassium hydroxide (KOH) solution to form the colloidal silica. Size distribution and solution zeta potential were measured by Particle Size Distribution (PSA). In this experiment, the results showed that the higher solution pH (affect the decreasing of zeta potential value) and higher colloidal concentration (affect the increasing of zeta potential value) play important role in the stability of colloidal silica and controlling the particle growth to form the larger particle size. The colloidal silica formed at this condition was agglomeration free for a long period that indicated the colloids were stable.