Silica, commonly known as silica, is a basic chemical compound. It has a wide range of applications in various industries. The true excellence of silica is its adaptability. Because its preparation methods are various. These different methods produce various types of silica. Each silica is customized for a specific use.
In this exploration, we will embark on a journey. Explore the various techniques used to synthesize different forms of silica. From the nitric acid method to rice husk carbonization, each method holds the key to creating variations of silica. Contribute to our daily lives and technological advancement. Join us to explore the interesting world of silica production.
1）Method for producing amorphous silica
Amorphous silica has a variety of industrial applications. It can be prepared in a series of five steps. They are silica gel preparation, granulation, sintering, cleaning, and drying. These processes can be summarized as follows:
1. Preparation of silica gel:
The first step in producing amorphous silica involves the preparation of silica gel. This can be achieved by hydrolyzing silicon tetrachloride (SiCl4) to form silica gel. Alternatively, organosilicon compounds such as tetramethoxysilane can be hydrolyzed to produce silica gel. Another method involves the vapor phase formation of silica gel.
2. Granulation:
The silica gel obtained in the first step is then dried and processed into granules. These particles are then pulverized. It is then sieved to get the desired average particle size of the amorphous silica.
3. Sintering:
Granular silica typically undergoes a sintering process at temperatures between 800°C and 1450°C. During the sintering process, a plasma is used to heat and melt the silica. It achieves the desired product characteristics.
4. Cleaning:
After the sintering process, the amorphous silica is cleaned. to remove any fine particles that may be present on the surface. This increases the purity of the final product.
5. Drying:
In the final step, the cleaned amorphous silica is dried thoroughly. Make sure the product does not contain moisture. Can be used in a variety of applications.
2）Production method of crystalline silica
Crystalline silica is usually obtained through a simpler process involving the following steps:
1. Mixing and sealing:
In this method, a mixture of silicon-containing raw materials (silicon source), water, structure-directing agents, and alkaline or acidic media is thoroughly mixed. and sealed in a high-pressure reaction vessel.
2. Heating and heat preservation:
The sealed container is then heated to a temperature between 100°C and 220°C. Then it is maintained at this temperature for a period ranging from 5 hours to 10 days. This controlled heating and holding time allows the desired crystalline silica to form.
3. Cooling:
After the reaction, the vessel is rapidly cooled, stopping the formation of crystalline silica.
4. Washing and drying:
The resulting crystalline silica is washed with water or dilute acid solution. Bring the pH to 8 to 11. The product is then dried to obtain the original powder.
5. Activate:
To enhance its properties, silica powder can be formed into various products by adding binders. It is then fired in a muffle or tube furnace to activate its specific properties.
3）Various Production Methods of SiO2 powder
There are many ways to produce silica. Each method is suitable for different applications and industries. These methods include the use of hydrochloric acid, salt, and carbonization processes. and nitric acid and combustion methods. The specific choice of production method often depends on cost-effectiveness. and factors such as the purity and performance required of the silica product.
Production methods must be tailored to the intended application. To ensure that the final silica product meets the required specifications and quality standards.
1. Hydrochloric Acid Method:
In the hydrochloric acid method, a diluted solution of sodium silicate is added to a neutralization tank. With continuous stirring, hydrochloric acid is introduced. Seed crystals are added to start the neutralization reaction. The resulting mixture is filtered, washed, and subjected to spray drying to get active silica.
2. Salt Decomposition Method:
In the salt decomposition method, a 13°Bé sodium silicate solution and an 8°Bé sodium chloride solution are mixed to initiate a salting-out process. This is followed by the addition of 31% hydrochloric acid (or sulfuric acid in the case of the sulfuric acid method). It results in the precipitation of fine silica gel. The gel is then subjected to water washing, dehydration, drying, crushing, and sieving to produce precipitated silica.
3. Carbonization Method:
The carbonization method involves the fusion of silica sand with pure alkali at high temperatures. This fused material is then dissolved. Carbon dioxide gas containing 30% to 35% CO2 is introduced to achieve carbonization and neutralization over 6 to 8 hours. Following washing, sulfuric acid is added to adjust the pH to a range of 6 to 8. A second washing is carried out. Then it is followed by dehydration, drying, and particle size reduction (to 200-350 mesh) to obtain the final precipitated silica product.
4. Rice husk method:
The rice husk method requires careful control of the carbonization of the rice husk. to remove organic matter and retain the hydrated silica within the rice husk. After carbonization, the rice husk is immersed in a sodium carbonate solution at a specified temperature and pressure. This results in the release of hydrated silica. The extraction rate is as high as 90%. The extracted hydrated silica is then filtered, washed, and spray-dried to obtain precipitated silica.
5. Combustion Method:
In the combustion method, purified silicon tetrachloride, hydrogen gas, and air are evenly mixed and introduced into a combustion chamber. Here, the reaction of hydrogen gas with oxygen in the air generates high-temperature water vapor. This results in the high-temperature hydrolysis of silicon tetrachloride to form silica. The aerosol silica in the combustion gas is directed into a condensation chamber. Where the silica condenses into particles. These particles are separated using a cyclone separator. Any residual gas is treated with ammonia or dry air to remove acid impurities, ultimately yielding gaseous silica.
6. Nitric Acid Method:
The nitric acid method is a specialized method for producing high-quality silica. Particularly suitable for applications requiring electronic-grade silica. The method relies on a controlled chemical reaction between a solution of sodium silicate (often called water glass) and nitric acid. The obtained silica undergoes many post-reaction treatments to get the required electronic-grade products.
6.1. Reaction process:
The process begins by preparing a sodium silicate solution. Sodium silicate solution is used as the silica source. This solution was gradually mixed with nitric acid. A controlled reaction between sodium silicate and nitric acid produces silica precipitate. This reaction is usually carried out under specific conditions. to ensure the required product quality and purity.
6.2. Washing:
After the reaction is complete, wash the silica precipitate thoroughly. This washing step is critical to remove any remaining impurities, unreacted chemicals, and by-products. It helps improve the purity of the resulting silica.
6.3. Acid treatment:
Acid treatment is an important stage in the nitric acid method. It involves exposing washed silica to acid. This further refines the material. This acid treatment can help cut any remaining contaminants. and enhance the chemical properties of silica.
6.4. Rinse with deionized water:
After acid treatment, the silica undergoes a rinsing process with deionized water. Use deionized water to minimize the introduction of any ionic impurities. This step is critical, especially for electronic grade silica. Because even trace amounts of impurities can adversely affect their performance in electronic applications.
6.5. Dehydration:
The final step involves removing excess water. and achieve the required moisture content for silica products. Dehydration is usually accomplished through a drying process. This step ensures that the electronic-grade silica is free of excess moisture. making it suitable for a variety of high-purity applications.
The nitric acid method is the preferred method for producing electronic-grade silica. Because it is capable of producing highly pure and refined materials. Electronic-grade silica is critical in the semiconductor industry and other high-tech applications. Even the slightest impurity can affect the performance of electronic components. So, the method’s meticulous approach, including acid treatment and deionized water rinses, plays a vital role in obtaining silica that meets the stringent standards required by these industries.
By controlling the entire production process from reaction to purification. The nitric acid method ensures the stringent requirements of electronic applications. Making it an important part of modern technology and electronic manufacturing.
These various production methods offer diverse advantages. They are employed according to the specific requirements of the end application. From hydrochloric acid to carbonization, the choice of method depends on factors like cost-effectiveness and desired product quality. From various applications, silica production processes continue to evolve. It ensures a steady supply of this versatile material.
