Aluminum hydroxide, both weak acid and weak alkali, has a wide range of applications in industry, can be used as a flame retardant, lubricants, etc.,aluminum hydroxideHow is it prepared, do you know? Let's find out.
At present, there are two methods for producing aluminum hydroxide in industry, Bayer method and soda lime sintering method.
a bayer method
After so many years of development, the preparation process of Bayer process has undergone many changes, but its principle has not changed. The principle of Bayer process is realized by using different temperatures and different reaction directions: under the condition of high temperature, the mixture of alumina is mixed into sodium hydroxide solution to obtain sodium aluminate solution, while impurities such as iron and silicon will not be dissolved in sodium hydroxide solution. After separation, the temperature is reduced to make the above formula reverse reaction to obtain aluminum hydroxide and sodium hydroxide mother liquor, which can be produced in the next round. This method is also generally used for industrial preparation of alumina, and the obtained aluminum hydroxide can be calcined and dehydrated.
dialkali lime sintering method
Soda lime sintering method is to calcine bauxite and limestone at high temperature to obtain sodium aluminate solid, and then gradually separate the obtained impurities, iron oxide to form easily hydrolyzed sodium ferrite, silicon oxide and titanium dioxide to form insoluble calcium silicate and calcium titanate in water. After separation, sodium aluminate solution is obtained, and then carbon dioxide is introduced to precipitate aluminum hydroxide. Aluminum hydroxide can also be prepared in this way.
Compared with the Bayer process, the soda-lime sintering process is cumbersome, the cost is higher, and the purity is low, but the soda-lime is of great significance for the treatment of bauxite with a relatively low ratio of alumina and silica.