The utilization of dye wastewater in enhancing catalytic activity of CeO2-TiO2 mixed oxide catalyst for NO reduction and dichloromethane oxidation

Abstract

Waste is a misplaced resource. Herein, anionic (orange II sodium salt and Ponceau 2R) and cationic (Rhodamine B and Methylene blue) dye wastewater assisted photo-treatment (referred as DAPT) method was developed to modify sol-gel synthesized CeO2-TiO2 (CeTi) mixed oxide catalyst. Catalytic activity test results showed that both anionic and cationic dye wastewater could be used as “fuel” of photo-treatment to enhance the activity of CeTi catalyst in NO reduction and dichloromethane oxidation. Characterization and DFT calculation results revealed that DAPT process increased the amount of Ce3+ ions on CeTi samples, which could induce the formation of Ce–VO–Ti (oxygen vacancy (VO) in Ce–O–Ti short range structure). These Ce–VO–Ti defects not only could be adsorption sites for NH3, dichloromethane and oxygen, but also promoted the redox shift of Ce3++ Ti4+ ⇋ Ce4++ Ti3+ by enhancing the oxidizability of Ce4+ and Ti4+ species. Furthermore, defects changed the polarity of Ce–O and Ti–O, which was conducive to the activation of lattice oxygen. All these improvements contributed to the excellent catalytic activity of CeTi catalysts. We expected this work to be instructive on constructing structure-activity over CeO2-TiO2 based catalysts and utilizing dye wastewater.