Titanium dioxide is produced by either the sulfate or the chloride process. Processing conditions determine the form (anatase or rutile structure) of the final product. 

 

• In the sulfate process, sulfuric acid is used to digest limonite (FeTiO3) or limonite and titanium slag. After a series of purification steps, the isolated titanium dioxide is finally washed with water, calcined, and micronized. 

 

• In the chloride process, chlorine gas is reacted with a titanium containing mineral under reducing conditions to form anhydrous titanium tetrachloride, which is subsequently purified and converted to titanium dioxide either by direct thermal oxidation or by reaction with steam in the vapour phase. Alternatively, concentrated hydrochloric acid can be reacted with the titanium-containing mineral to form a solution of titanium tetrachloride, which is then further purified and converted to titanium dioxide by hydrolysis. 

 

The titanium dioxide is filtered, washed, and calcined. Commercial titanium dioxide may be coated with small amounts of alumina and/or silica to improve the technological properties of the product.