There are many methods for preparing acidic silica sol, mainly including the following:
1. Ion exchange method
Ion exchange method is a common method for preparing acidic silica sol. This method uses water glass as the main raw material, removes sodium ions and other cationic impurities in the solution through ion exchange resin, and obtains a dilute polysilicic acid solution. Then add a stabilizer to adjust the pH value, so that the polysilicic acid solution undergoes the formation of crystal nuclei and the growth of grains to obtain a mother liquor. Finally, the polysilicic acid solution is added to the mother liquor at a certain rate to obtain a monodisperse silica sol with controllable particle size.
2. Sol-gel method
The sol-gel method is to dissolve the silicate raw material in a solvent to form a sol, then obtain a gel through a gelation reaction, and finally obtain a silica sol after drying and heat treatment. This method can prepare acidic silica sol with high purity and high stability, but the process is relatively complicated and the cost is high.
3. Electrolytic electrodialysis method
The electrolytic electrodialysis method is to generate monosilicic acid in the electrodialysis cell by regulating the pH, current density, temperature and other conditions of the electrolyte solution, and form silica sol under the action of polymerization reaction. The silica sol particles prepared by this method are uniform, but the electrolysis conditions need to be strictly controlled.
4. Chemical precipitation method
The chemical precipitation method is to add acid or alkali to the silicate solution to cause the silicate to precipitate and generate silica sol. This method has a simple process, but the size and distribution of the prepared silica sol particles are difficult to control.