How is Low Sodium Type Colloidal Silica/Silica Sol prepared?

Low Sodium Type Colloidal Silica/Silica Sol is an important industrial raw material. It is widely used in many fields such as coatings, ceramics, food and medicine due to its good stability and versatility. The following will introduce the preparation method of low sodium type colloidal silica in detail, including raw material selection, preparation process and key parameter control.

1. Raw material selection
The raw materials for preparing low sodium type colloidal silica are mainly as follows.
Silicon source: Commonly used silicon sources are sodium silicate, ammonium silicate and silica powder. When selecting a silicon source, its purity and sodium ion content should be given priority.
Water: Pure water is the main solvent in the preparation process, and it is necessary to ensure that the water quality meets the experimental requirements.
Acid or alkali: Acid and alkali agents for adjusting pH value, commonly used are hydrochloric acid, ammonia water or acetic acid.

2. Preparation process
The preparation process of low sodium type colloidal silica mainly includes the following steps:
Hydrolysis reaction: Dissolve the selected silicon source in pure water to form a transparent solution. Taking sodium silicate as an example, it can be dissolved in water and then the pH value can be adjusted by adding dilute hydrochloric acid drop by drop. The pH value is controlled in the range of 6 to 9 to ensure the smooth progress of the reaction.
Gelation process: As the pH value is adjusted, the silicate ions in the solution begin to polymerize and form small particles. This process is called gelation. At this stage, stirring should be continued to maintain the uniformity of the solution and prevent the particles from settling.
Temperature control: During the gelation process, the reaction temperature has an important influence on the formation and stability of the particles. Generally, the reaction temperature is controlled between room temperature and 80 degrees Celsius to promote the growth of particles and improve their uniformity. High temperature helps to accelerate the reaction, but excessive temperature should be avoided to cause particle agglomeration.
Stabilization treatment: In order to improve the stability of the colloid, the solution after the reaction needs to be treated. Stabilizers (such as surfactants) can be added to prevent the aggregation and precipitation of particles. The choice of stabilizer should be adjusted according to the specific application requirements to ensure the stability of the final product.
Filtration and washing: After the reaction is completed, the solution may contain unreacted silicon source and other impurities. At this time, these impurities need to be removed by filtration or centrifugation. The filtered colloid needs to be washed several times with pure water to remove residual sodium ions and other impurities to ensure the purity of the final product.

3. pH and concentration adjustment
During the preparation process, pH is a key parameter. Too high or too low pH will affect the formation and stability of the colloid. Therefore, the pH value needs to be tested and adjusted regularly. In addition, the concentration of the final product also needs to be adjusted according to the application requirements, usually controlled between 10% and 30%.

4. Storage and use
After preparation, low-sodium colloidal silica should be stored in a cool, dry environment, away from direct sunlight and high temperature. When using, it needs to be fully stirred to ensure the uniformity of the colloid, and follow the relevant instructions for use in the application.