Preparation Of Fe⁰/MnO_x/BiVO₄ And Application Of Photocatalysis-Fenton Coupling Catalysis

Semiconductor photocatalysis technology is considered to be one of the most promising green technologies applied in the field of environmental pollutant degradation.Bi-based semiconductors,such as BiVO₄,Bi₂Mo O₆,Bi₂O₃,and Bi₂S₃,have band gaps of less than 3.0 e V and can be excited by visible light,so they are considered promising for removing pollutants from water and air.In this study,the monoclinic scheelite BiVO₄decahedron is synthesized by hydrothermal method.On this basis,two composite photocatalysts,MnO_x/BiVO₄ and Fe⁰/MnO_x/BiVO₄,are prepared by hydrothermal and photodeposition methods,so as to improve the inherent defects of pure BiVO₄ by adjusting crystal plane engineering and constructing heterojunction strategies.The main exposed surfaces of decahedron BiVO₄ at different positions correspond to the?010?and?110?planes respectively.Because the conduction and valence bands of the two crystal planes have different energies,different driving intensities are generated,so that photogenerated electrons and holes can preferentially dissociate and gather on?010?and?110?planes,respectively.The oxidation promoter MnO_x can be selectively deposited on the?110?crystal surface.Manganese oxide not only has good oxidation performance,can provide excellent synergistic effects,but also its band structure can be well matched with BiVO₄.In the photocatalytic process,photogenerated holes accumulated on the?110?crystal plane of BiVO₄ can be transferred and accumulated in MnO_x,thereby achieving further charge separation and inhibiting photocarrier recombination.To degrade highly toxic and persistent organic pollutants,Fenton technology is introduced into the photocatalytic system.The Fenton catalyst includes nano zero-valent iron?Fe⁰?.Nano zero-valent iron reacts with free hydrogen ions in water to transform into Fe²⁺cations.H₂O₂ produced during the photocatalytic reaction can form a Fenton reaction with Fe²⁺,thereby coupling photocatalytic technology and Fenton reaction.In this paper,two composite photocatalysts,MnO_x/BiVO₄ and Fe⁰/MnO_x/BiVO₄,were prepared.Use XRD,XPS,UV-vis,SEM,TEM and other characteristics to test the prepared samples.The target organic pollutants of the photocatalytic degradation experiment in this paper are bisphenol A and 2,4-dichlorophenol.The research results include:?1?Solvothermal synthesis of BiVO₄ from bismuth nitrate and ammonium metavanadate.Manganese sulfate was used as the manganese source and potassium iodate was used as the electron acceptor to selectively deposit MnO_x on the?110?crystal plane of BiVO₄.Thus,a binary composite photocatalyst with strong photocatalytic activity was synthesized,and the degradation rate of BPA and 2,4-DCP reached 41.8%and 47.6%,respectively.?2?Nano zero-valent iron particles were prepared by a chemical reduction method,and then the synthesized MnO_x/BiVO₄ binary composite decahedron was mixed with the prepared nano zero-valent iron in an ethanol/water solution for hydrothermal reaction to obtain Fe⁰/MnO_x/BiVO₄ ternary composite photocatalyst.The problems of a single semiconductor photocatalyst are solved by the presence of Fe⁰ and MnO_x,and Fenton advanced oxidation technology has also been successfully introduced,so that the final material can produce a sufficient amount of active substances to achieve excellent photocatalytic degradation activity.Under the condition that the visible light is incident light,the degradation rate of the final product Fe⁰/MnO_x/BiVO₄ to bisphenol A and2,4-dichlorophenol is 91.4%and 95.4%,respectively.