The main raw materials for precipitated white carbon black (hydrated silica) include sodium silicate (water glass), sulfuric acid (or other acids such as hydrochloric acid, carbon dioxide, etc.), and optional additives (such as surface modifiers, crystal control agents, etc.). According to the different raw materials and production processes, the production methods of precipitated white carbon black are mainly divided into the following types:
Sulfuric acid method (acid method)
Raw materials: sodium silicate (water glass), sulfuric acid.
Production method: Mix sodium silicate solution with sulfuric acid, and generate silica precipitate by controlling the pH value and reaction conditions. The precipitate is filtered, washed, dried, and crushed to obtain white carbon black products.
Characteristics: The sulfuric acid process is mature, the production cost is low, the product purity is high, and it is suitable for large-scale production. But the by-products generated by the sulfuric acid method (such as sodium sulfate) need to be treated, which may have a certain impact on the environment.
Hydrochloric acid method
Raw materials: Sodium silicate (water glass), hydrochloric acid.
Production method: Similar to sulfuric acid method, but using hydrochloric acid as a precipitant. The hydrochloric acid method can reduce the generation of by-products in some cases, but the cost of hydrochloric acid is high and it is highly corrosive to equipment.
Features: The product has high purity, but the production cost is high, making it suitable for applications that require high purity.
Carbon dioxide method (carbonization method)
Raw materials: Sodium silicate (water glass), carbon dioxide.
Production method: Inject carbon dioxide into a sodium silicate solution to produce sodium carbonate and silica precipitates. The precipitate is processed to obtain white carbon black product.
Characteristics: The carbon dioxide method has good environmental friendliness, and the by-product is sodium carbonate, which can be recycled and reused. However, the carbon dioxide method has a slower reaction rate and lower production efficiency, making it suitable for scenarios with higher environmental requirements.
Nitric acid method
Raw materials: Sodium silicate (water glass), nitric acid.
Production method: Similar to sulfuric acid method, but using nitric acid as a precipitant. The byproduct produced by the nitric acid method is sodium nitrate, which is difficult to treat.
Characteristics: The nitric acid method has a high cost and strong corrosiveness to equipment, making it less commonly used.
 Sol gel method
Raw materials: silicates (such as ethyl orthosilicate), water, catalysts (such as acids or bases).
Production method: through the sol gel process, the silicate ester is hydrolyzed to produce silica sol, and then through gel, drying, calcination and other steps, white carbon black with high purity and high specific surface area is obtained.
Characteristics: The sol-gel method can accurately control the microstructure of the product (such as pore size, specific surface area, etc.), and is suitable for application fields that require high product performance (such as catalyst carriers, high-performance rubber reinforcing agents, etc.). But the process is complex, the cost is high, and the production efficiency is low.