Novel Process for Titanium Dioxide Production from Titanium Slag: NaOH-KOH Binary Molten Salt Roasting and Water Leaching

Titanium dioxide (TiO2) has been widely used as pigment in paints, fillers for plastic and paper, coatings, adsorbents, cosmetics, catalysts, and gas sensors. A novel process for TiO2 production has been developed by the Institute of Process Engineering. This work develops the novel process by using the NaOH/KOH binary molten salt (50 mol % NaOH, 50 mol % KOH) instead of NaOH molten salt. Under conditions of temperature 350 degrees C and mixed alkali-to-titanium slag ratio 1.4:1, the titanium conversion ratio obtained is >98% with reaction time around 90 min. The kinetics investigation indicates that the decomposition of titanium slag is controlled by mass diffusion in thed residual layer and the apparent activation energy is 43.1 kJ/mol. 98% of KOH and 86% of NaOH can be recycled by a water leaching process. On the basis of the experimental results, a flow sheet was developed and tested, and the content of TiO2 obtained in the product reached 99.5%. As the NaOH/KOH binary molten salt system provides a liquid as relatively low temperature, the energy consumption of this technology may probably be lower than that of the existing one.