A new method for production of titanium dioxide pigment

Titanium dioxide (TiO2) has been widely used as pigment in paints, paper and cosmetic products, as well as high-tech applications such as solar cells, semiconductors, biomedical devices and air purification. TiO2 pigment is primarily produced by a high temperature chloride process, which forms CO2 as a reaction byproduct. A novel hydrometallurgical process for making TiO2 pigment without direct CO2 emission is investigated. The novel process involves alkaline roasting of titania slag, with subsequent washing, leaching, solvent extraction, hydrolysis, and calcination stages, resulting in high-purity anatase or rutile pigments. Experimental validation for each of the processing steps is demonstrated. Pigment whiteness is critically sensitive to trace amounts of discoloring impurities such as iron. The use of solvent extraction proved to be highly effective in reducing the concentration of discoloring impurities in the final pigment to commercially acceptable levels.