A potentially more eco-friendly chemical pathway for production of high purity TiO2 from titanium slag

摘要： TiO2 is an important inorganic material which is commercially produced by either the chloride or the sulfate process. In general, the latter has lower cost and lower entry barrier than the former. However, the environmental impact associated with the sulfate process is more visible than the chloride process because the sulfuric acid with a low concentration (~20 wt%) cannot be cost-effectively recycled; therefore, it has to be neutralized, generating a large amount of wet and useless red gypsum (RG). In this research, a potentially more eco-friendly chemical pathway for TiO2 production from concentrated titanium ore, aka titania slag, is presented. The new method consists of three critical steps including transformation of the titania slag to a lower valence titanium sub-oxide by aluminothermic reduction, digestion by using mild acid, and controlled hydrolysis accompanied by acid recycling. As a result of the phase transformation, the digestion of titanium from the titanium feedstock becomes easier such that it is feasible to use relatively mild acid to replace concentrated acid, reducing the environmental impact from the red gypsum because the need for neutralizing the waste acid can be eliminated. High purity hydrous TiO2 can be prepared after hydrolysis, and the spent liquor can be effectively recycled back to the digestion unit.