Visible photocatalytic degradation of tetrabromobisphenol A by CuO-modified Ce2O3: Mechanisms and DFT studies

Abstract

The widespread use of brominated flame retardants poses serious hazards to environment and health. In this study, CuO/Ce2O3 nanocomposites were synthesized by a coprecipitation method. Various characterization methods and density functional theory (DFT) calculations were used to analyze the composition and surface structure of material. Under visible light, the prototypical pollutant, namely, tetrabromobisphenol A (TBBPA) exhibited the highest degradation efficiency of 80.46% after 120 min with a CuO/Ce2O3 ratio of 1:20. The photocatalytic degradation mechanism of TBBPA in the CuO/Ce2O3 system was comprehensively investigated. Radical scavenging experiments showed that h+ is the primary active substance in TBBPA photodegradation, and·OH and·O2− are secondary contributors. Moreover, the Fukui index was used to predict the active site, and DFT methods were used to calculate the degradation mechanism of TBBPA. Combined gas chromatography/mass spectrometry and high-performance liquid chromatography-mass spectrometry showed that the possible degradation pathways of TBBPA were determined to be debromination, C–C bond breaking, and ring-opening. Ecotoxicity evaluation showed that degradation products have significantly lower acute toxicity than TBBPA. The excellent reusability and stability of CuO/Ce2O3 indicate that this system can be successfully applied in water treatment, which is of great significance for the environmentally-friendly removal of TBBPA.