Environmentally-friendly harvesting TiO2 nanospheres and V2O5 microrods from spent selective catalytic reduction catalysts

Spent selective catalytic reduction (SCR) catalysts are defined as hazardous wastes because of the toxicity of V2O5 to the ecological environment. Recycling of V2O5 and TiO2 from the spent SCR catalysts has strikingly social and environmental benefits as well as economic values. In this work, a "NaOH + Na2CO3" system was employed to recycle 99.2% of anatase/rutile TiO2 nanospheres with a nanospherical morphology from the spent SCR catalysts by a simple sintering-leaching process. The observed photocatalytic performance of anatase/rutile TiO2 nanospheres was higher than that of the other TiO2 recovered from the spent SCR catalysts, commercial TiO2, and chemosynthetic TiO2, which can be ascribed to the enhanced separation of photo-excited electron/hole in a direct Z-scheme of anatase/rutile TiO2 homostructures. Additionally, high-purity V2O5 microrods with high H2S removal performance were efficiently prepared by a hydrothermal method in the leaching solution, which is superior to the traditional method including NH4VO3 precipitation and solvent extraction as the present method can recycle vanadate from low-grade filtrate with a 99.6% of recovery rate. This study develops an alternative method for controlling pollution of vanadate to soil and water and recycling of valuable metals.