Effect of ZrO2 on the phase relations for CaO-SiO2-TiO2 system related to efficient extraction of titanium from titania-bearing slag

The selective crystallization and phase separation process has been regarded as a promising process for the recycling of titanium from titania-bearing furnace slag, however, the composition modification mechanism still remains unclear due to the lack of fundamental thermodynamic data. In the present work, the influence of ZrO₂ addition on the equilibrium phase relations and the 1400 °C isotherm for CaO-SiO₂-TiO₂ system were experimentally determined by using the high temperature equilibration-quenching technique, and Scanning Electron Microscopy-Energy Dispersive X-ray Spectrometry, and X-ray diffraction analysis. The equilibrium solid phases of rutile (TiO₂), perovskite (CaTiO₃), and tridymite (SiO₂) are determined to be coexisting with the liquid phase. In addition, comparisons of present results with thermodynamic calculation by FactSage show significant discrepancies. The present work is important for enriching the thermodynamic database of titania-bearing slag oxide systems as well as optimizing the selective crystallization and phase separation process.