Manufacture of hydrated titanium dioxide--the basic principle of hydrolysis of titanium liquid

Hydrated titanium dioxide can be written formula TiO ₂ · H ₂ O or _{H 2 TiO 3, TiO (OH} ) 2, also known as metatitanic acid or titanium hydroxide. The manufacture of hydrated titanium dioxide is a core part of the process for the production of titanium dioxide by sulfuric acid, and is one of the most demanding places for process control. It is the black titanium sulfate solution (titanium sulfate solution), by heating the hydrolysis, a white precipitate was precipitated hydrous titanium oxide from the mother liquor, the mother liquor so that other soluble metal impurity ion separation, to facilitate the further purification of titanium dioxide. The quality of the hydrolysate not only affects the normal operation of the post-process, but also directly affects the quality of the final product, often resulting in irreparable quality loss. In the production of pigment grade titanium dioxide, the requirement for hydrolysis is that the hydrolysate must first be precipitated with hydrated titanium dioxide having a certain particle size, uniform particle distribution, easy filtration and washing, and secondly, it is desirable to have a higher hydrolysis rate and simple equipment. Technical and economic indicators such as easy operation, because the particle properties of hydrated titanium dioxide directly determine the optical properties and pigment properties of titanium dioxide. Therefore, it is reasonable to say that the hydrolysis process of the titanium sulfate solution is called the preparation process of the hydrated titanium dioxide particles.

The hydrolysis mechanism of titanium liquid is very complicated, and its chemical reaction formula can be simply as follows:

Ti(SO ₄ ) ₂ +H ₂ O→TiOSO ₄ +H ₂ SO ₄ (1)

TiOSO ₄ +2H ₂ O→H ₂ TiO ₃ ↓ +H ₂ SO ₄ (2)

In the above chemical reaction formula, the formula (1) is scarcely present or rare, because when the F value of the titanium liquid in industrial production is less than 2.45, the solution should be mainly TiOSO ₄ . Theoretically speaking, only TiOSO ₄ will be hydrolyzed to form H ₂ TiO _{3 in} a neutral aqueous solution containing no free acid. In fact, not only does the titanium liquid contain a large amount of free acid, but also releases free acid during hydrolysis. Therefore, the hydrolyzate of the titanium liquid is not only H ₂ TiO ₃ but also TiOSO ₄ . If TiOSO _{4 is} represented by TiO ₂ ·SO ₃ and H ₂ TiO _{3 is} represented by TiO ₂ ·H ₂ O, the product of hydrolysis of titanium liquid is actually a series of water and a certain amount of SO ₃ titania colloidal aggregate , the molecular formula should be TiO ₂ ·xH ₂ O·ySO ₃ , so the correct name should be hydrated titanium dioxide, wherein the relationship between TiO ₂ , H ₂ O, SO ₃ , ie the values ​​of x and y depends on the hydrolysis conditions, The value of F in the solution varies.

Since titanium hydroxide has amphoteric characteristics and is acidic, it can be called titanic acid, in which Ti(OH) _{4 is} called a titanic acid or orthotitanic acid; TiO(OH) ₂ is called beta titanic acid or metatitanic acid. Usually, for the convenience of memory and writing, it is customary to always refer to hydrated titanium dioxide as metatitanic acid and write it as H ₂ TiO ₃ .