Silica sol is a colloidal solution in which colloidal particles of silicon dioxide are dispersed in water, also known as silica sol or silica hydrosol. The appearance is mostly milky white or light blue transparent solution. Most of them are stable alkaline, and a few are acidic. The concentration of SiO2 in silica sol is generally 10%~35%, and can reach 50% when the concentration is high. The specific surface area of silica sol particles is 50~400m2/g, and the particle size range is generally 5~100nm, that is, it is at the nanoscale. Compared with the general emulsion with a particle size of 0.1~10μm, its particles are much smaller.
The production process of silica sol mainly includes the following methods:
Ion exchange resin method: This method uses ion exchange resin to treat dilute sodium silicate solution and prepare silica sol by removing sodium ions in the solution. Ion exchange resins are usually cross-linked organic polymers containing active acidic groups, such as sulfonic acid groups and carboxyl groups. The H+ ions in these resins can be ionized and exchanged with other cations to finally obtain silica sol.
Sulfuric acid neutralization method: This method uses sulfuric acid to neutralize a dilute solution of water glass, and prepares silica sol by controlling the pH, temperature and other conditions of the solution. Under appropriate conditions, the crystal nucleus grows further, and then the silica sol product can be obtained by concentration and purification. The whole process requires strict control of process conditions such as the Na+ concentration in the mixed solution, the heating temperature, the pH of the solution and the addition time.
Electrolysis electrodialysis method: This method prepares silica sol through an electrochemical process. Electrolyte raw materials are added to the electrodialysis cell, and monosilicic acid H4SiO4 is generated by regulating the pH, current density, temperature and other conditions of the electrolyte solution, and crystal nuclei are formed under polymerization reaction, and finally the silica sol product is formed. The process flow of the electrolysis electrodialysis method includes the steps of placing the electrolysis electrodialysis cell, adding electrolyte raw materials, and electrifying the electrolysis electrodialysis process.
Other methods: In addition to the above methods, there are other methods for preparing silica sol, such as the gelation method, the gas phase silica method and the dispersion method. These methods each have their own unique process flow and application conditions.
In order to cope with the current downturn in the silica market, break through the communication barriers between the upstream and downstream of the silica sol industry, and promote technical exchanges between enterprises, SAGSI has decided to establish a silica sol technology and application exchange group. This group will regularly publish silica sol industry information, industry activities, release corporate needs, and discuss the latest technological progress. Upstream and downstream related companies are welcome to join the group to participate in technology, supply and demand, industry information and other exchanges.
