Purification of titanium purposes
After settling to remove most of the residue, after freezing crystallization to remove the ferrous sulfate crystals, but the titanium solution still contains some incomplete precipitation brought over the trace solid phase, these solid phase impurities particles very fine, ferrous sulfate Crystal coarse filter, the filter cloth can be left in the titanium liquid, the surface may have a certain charge, leaving it in the titanium liquid will cause the following two hazards.
1. Affect the particle structure of hydrolyzate, resulting in metatitanic acid washing difficult and poor pigment performance.
Titanium hydrolysis process is to first form a group of crystallization centers, these crystalline centers gradually grow, and eventually become a solid precipitated. The crystallization center is a colloidal substance that has some influence on the particle structure of the hydrolyzate. In order to obtain the desired hydrolyzate, the crystalline center must be prepared as required. However, the colloidal solid-phase impurities in the titanium solution act as a crystallization center when the titanium solution is hydrolyzed. However, this kind of crystallization center is unsatisfactory and is an undesirable or irregular crystallization center that affects the hydrolysis The product of the particle structure, so that the irregular shape, the particle surface is not smooth, with edges and corners, resulting in metatitanic acid poor washing effect, but also affect the product's pigment properties.
2. Adsorption of metal ions, pollution of finished products, reduce purity, affect the whiteness.
Since these solid-phase impurities are charged colloidal particles, they adsorb certain metal ions. As they become crystalline centers during hydrolysis, these adsorbed metal ions are eventually incorporated into finished products as they enter the interior of the hydrolysable metatitanic acid particles, reducing the purity of the finished product. And some colored harmful metal ions such as vanadium, chromium, manganese, lead, drilling, etc., will also affect the whiteness of the product.
To this end, in the production of titanium dioxide pigment, you must make a frame filter press, the removal of these solid-phase impurities.