Recycled TiO2 from the deactivated SCR catalysts for the CaCO3-TiO2 composite opacifier and its function in the zirconium-free glaze system.

[Display omitted] • The deactivated SCR catalyst used as Ti resources to prepare CaCO 3 -TiO 2 composite opacifier has great significance in achieving the recycling of the spent SCR catalysts. • The composite has the same opacifying performance as ZrSiO 4。 • Compared with ZrSiO 4 , CaCO 3 -SCR in the field of sanitary ceramics can reduce the costs and avoid the radiation in the glaze containing zirconium. • The composite opacifier avoids the yellowing when only TiO 2 is as opacifier because CaCO 3 -TiO 2 composite can promote the formation of sphene. A CaCO 3 -TiO 2 composite (CaCO 3 -SCR) was prepared by a facile mechanochemistry method using CaCO 3 and TiO 2 from the deactivated SCR catalysts. The results show that the CaCO 3 -SCR composite as opacifiers exhibits excellent opacifying performance. The FT-IR results indicate that -Ca-O-Ti- bonds existing between CaCO 3 and TiO 2 from the deactivated SCR catalysts combine them. The main opacifying phase is the sphene phase with particles size about 0.5–1 μm. Moreover, no excess crystalline TiO 2 was observed in the glaze, indicating that fixing TiO 2 is the key to preventing glaze from yellowing. [ABSTRACT FROM AUTHOR]