Efficient removal of 2,2′,4,4′-tetrabromodiphenyl ether with a Z-scheme Cu2O-(rGO-TiO2) photocatalyst under sunlight irradiation
Z-scheme Cu 2 O-(rGO-TiO 2 ) photocatalyst was successfully synthesized via a simple three-step approach for 2,2′,4,4′-tretrabromodiphenyl ether (BDE47) reductive removal under simulated solar irradiation. Unlike the traditional heterojunction , the addition of reduced graphene oxide (rGO) enhanced the redox ability of Cu 2 O-TiO 2 by increasing charge transfer. When modifying Cu 2 O films by adding 1% rGO and coating with 70% TiO 2 , the resulting Cu 2 O-(rGO-TiO 2 ) exhibited the best photocatalytic activity for BDE47 removal. The charge transfers of Cu 2 O-(rGO-TiO 2 ) were proven to follow a Z-scheme pathway through the electron paramagnetic resonance analysis. The degradation pathways of BDE47 were elucidated by identifying intermediate products via gas chromatography-mass spectrometry (GC-MS) and gas chromatography (GC). Photo-electrons (e − ) generated from the conduction band of Cu 2 O and hydrogen protons (H 0 ) reduced from H + in water were the main contributing elements for the removal of BDE47, which response to the ortho and para debromination . Ortho-Br of BDE47 was attacked by e − and BDE28 was the dominant debromination product on the first stage. Then e − and H 0 attacked ortho-Br and para-Br of BDE28 to form BDE15 and BDE8, respectively. The concentration of BDE8 was higher than that of BDE15, suggesting that H 0 played the most important role on the second debromination stage. An effective Cu 2 O-(rGO-TiO 2 )-based Z-scheme system for BDE47 debromination was proposed in this study, which may contribute to the development of novel green technologies.
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