At present, there are mainly two methods for preparing silica. One is the precipitation method, and its general process route is:
First, quartz sand is reacted with soda ash at high temperatures using fuel oil or gas to produce industrial water glass. The industrial water glass is then mixed with water to form a dilute solution of a certain concentration. Under certain conditions, a certain acid is added to precipitate silicon dioxide. After cleaning, filtration, drying, and crushing, the product silica is obtained. The precipitation method can be further divided into many different specific methods such as acid method, sol method, carbonization method, etc.
In China, the acid method is mainly adopted. The acid method involves reacting soluble silicates with sulfuric acid (or other acids). When the reaction solution reaches a certain pH value, the acid addition reaction is stopped, followed by aging. Then, the mixture is filtered and repeatedly washed with water to remove Na2SO4. After that, it is sent for drying and grinding to obtain the product.