Synthesis Of Carbon Materials Coupled With Bismuth Oxyiodide Photocatalysts For The Typical Emerging Pollutants Photocatalytic Degradation Under Visible Light: Efficiency And Mechanism

Pharmaceutically active compounds（Ph ACs）and endocrine disrupting chemicals（EDCs）as the representative emerging pollutants are frequently detected in the real water matrices.Their pseudo persistence and bioconcentration ability have great potential risks to aquatic safety and human health.In this study,bisphenol A（BPA）,antipyrine（ANT）,tetracycline（TC）and ofloxacin（OFL）were selected as the target pollutants.Carbon materials including titanium carbide（Ti₃C₂）with strong surface coupling ability and multi carbon nanotubes（MWCNTs）with superior conductivity ability were used as modifiers.Therefore,a series of visible-light-driven（VLD）carbon materials coupled bismuth oxyiodide（Bi_xO_yI_z）-based photocatalysts with excellent photocatalytic efficiency and stability were designed systematically.The enhanced mechanism by Ti₃C₂ and MWCNTs were investigated from the aspects of structural design,interface coupling of carbon materials,separation of photogenerated charge carriers on the surface/bulk phase,and the formation of reactive species（RS）.Results showed that the low valence Ti sites have a strong redox reaction with the 2D BiOI nanosheets,which could induce the generation of Bi⁰ and in-situ oxygen vacancies（OVs）.The“electron trap”characteristics of OVs and the surface plasmon resonance effect（SPR）of Bi⁰ can promote the visible light absorption of the catalyst,thus increasing the separation of photogenerated carriers.MWCNTs with strong surface electron conductivity ability were coupled with 3D BiOI,Bi₄O₅I₂ and Bi₅O₇I nanosheets through interface amidation linkage.Photogenerated charge carriers can be transferred to the surface of MWCNTs,effectively reducing its recombination.Meanwhile,MWCNTs can regulate the facet ratio of（312）and（004）in Bi₅O₇I crystal phase.The“S-scheme”facet heterojunction of（312）/（004）is the key to improve the utilization of photogenerated carriers.The photocatalytic efficiency and degradation mechanism of target pollutants by carbon materials coupled Bi_xO_yI_z-based photocatalysts showed that the first-order reaction rate constant(k_obs)of 0.2 g/L Ti₃C₂/BiOI for ANT（3.0 mg/L）and BPA（5.0 mg/L）increased significantly to 0.0073 and 0.0261 min^-1,respectively compared with 2D BiOI nanosheets(0.0031 min^-1).The photocatalytic efficiency for ANT and BPA was increased by 2.4 times and 18.6 times,respectively,and the dissolution of iodine ions was less than 8.0 mg/L.Under the same reaction conditions,the k_obs of 3D flower like MWCNTs/BiOI nanosheets for ANT increased to 0.0061 min^-1,which is 1.94 times high than 2D BiOI nanosheets.The dissolution of iodine ion was reduced to less than 4.0 mg/L.Compared with pristine Bi₄O₅I₂,the k_obs of0.2 g/L MWCNTs/Bi₄O₅I₂ for ANT further increased to 0.0136 min^-1,and the dissolution of iodine ion decreased to 2.79 mg/L.The k_obs for TC photodegradation also increased significantly to 0.0116 min^-1,which is 2.32 times than pristine Bi₄O₅I₂.The k_obs of MWCNTs/Bi₅O₇I for OFL（10 mg/L）photodegradation was increased by 2.8 times higher than that of pristine Bi₅O₇I,and the dissolution of iodine ion was reduced to less than 1.5 mg/L.Although its photodegradation efficiency for ANT was not improved significantly under visible light,the k_obs could be significantly increased to 0.0136 min^-1 under simulated sunlight,reducing the formation risk of iodinated by-products.Radical trapping experiments showed that photogenerated hole（h⁺）and superoxide radicals（·O₂^-）were dominated role in photocatalytic process,and a small amount of RIS（·I,·I₂^-）was generated at the same time.Due to the high electron cloud density of the N atom connected to the methyl group on the pyrazolone ring,the first step of ANT is to form ANT^·+.Then,the substitution reaction occurred between ANT^·+and RIS to form ANT-I.