Production And Concentration Of Fine Colloidal Silica By Electrodialysis

The aim of our experiments was to verify the possibility of preparation and concentration of colloidal silica using an electrodialysis unit and membranes RALEX (R). The experimental conditions for the preparation of initial solution suitable for electrodialysis by utilization of phosphoric(V) acid were optimized. A proper control during the following concentration steps was suggested and a fine high-purity colloidal solution of concentration up to 10 % w/w (SiO2/water) was successfully prepared. Concentrated solution evinced good long-term stability. Phenomenon that provides stabilization during concentration step is described. We have observed that pH control during electrodialysis process is crucial to prevent membranes clogging and influences overall stability at laboratory condition. Size characterization of the colloidal system was carried by dynamic light scattering. Measured average particles size of colloidal solution was 9 nm.