Recovery model for the extraction of a high-grade Ti-fraction from processing residues

Due to its high refractive index, TiO₂ is widely used in coatings and paints. Globally, two major industrial processes are used to produce pure TiO₂ from primary titanium ores. For rutile, the chloride process is applied by mixing finely ground ore with coke and chlorine at temperatures up to 1200 °C. In this process, titanium is reduced and converted to volatile TiCl₄, enabling the removal of impurities and production of highly pure TiO₂. However, the process also generates significant residues, mainly consisting of unreacted materials as TiO2, coke and, SiO₂ polymorphs.

To recover the TiO₂ and coke from the stream, floating by water as dense media is used to produce a concentrate of acceptable Ti grade, though large amounts of impure middlings are also generated. These fine-grained middlings are commonly used as low-value filler in concrete applications (approx. €1/t).

In this study, we present a detailed quantitative mineralogical analysis of the middlings fraction using automated mineralogy (AM), X-ray diffraction (XRD), and X-ray fluorescence (XRF). The data show a correlation between TiO₂ content, density, and particle size. Laboratory air jet sieving allowed the separation of a 63–125 µm fraction containing TiO₂ at ore-grade levels. This simple but effective method demonstrates that low-value middlings can be upgraded to a high-value Ti resource (approx. €400/t).

This study highlights how combining mineralogical characterization with basic processing techniques can significantly improve the economic value of industrial residues.