The preparation methods of cationic silica sol mainly include hydrothermal method, sol-gel method and reverse microemulsion method. These methods have their own advantages and disadvantages, and the specific selection depends on the characteristics and application fields of the required cationic silica sol.
Hydrothermal method
The hydrothermal method is a method for preparing silica sol by hydrothermal reaction under high temperature and high pressure. During the hydrothermal reaction, the silicon source (such as sodium silicate, ethyl silicate, etc.) undergoes hydrolysis and polycondensation reaction in a high temperature and high pressure aqueous solution to form nano-silica particles. By adjusting the reaction conditions and subsequent processing steps, silica sols with different particle sizes and charge properties can be obtained. When preparing cationic silica sol, it is usually necessary to introduce cations (such as Al3+) into the reaction system so that they are bonded to the silicate on the surface of the silica sol particles to form a positively charged silica sol.