BiVO₄ Composite Photocatalyst Activating Peroxymonosulfate Under Visible Light For Degradation Of Tetracycline

The photocatalytic technology has relatively mild reaction conditions and can completely remove organic pollutants,and is widely used in the treatment of antibiotic residues.As a photocatalyst,bismuth vanadate（Bi VO₄）has a good response to visible light and abundant active sites,which has become a research hotspot in the field of visible light photocatalysis,but the easy recombination of photogenerated carriers limits the application of this material.In order to improve the separation efficiency of photogenerated carriers of Bi VO₄,in this paper,the effect of the built-in electric field of Bi VO₄ heterophase junctions on the photocatalytic performance was studied;through the the crystal face regulation of Bi VO₄ and Fe（II）loading,the efficient activation of peroxymonosulfate（PMS）improves the degradation efficiency of tetracycline.（1）By adjusting the p H value of the precursor solution,Bi VO₄ photocatalysts with different composite ratios of monoclinic and tetragonal phases were synthesized,and a direct Z-type mt-BVO-35%m heterophase junctions with visible light response was constructed.By adjusting the ratio of monoclinic Bi VO₄ to tetragonal Bi VO₄,the built-in electric field strength at the heterophase junctions can be adjusted,thereby regulating the photocatalytic activity.When the proportion of monoclinic phase is 35%,the built-in electric field strength of mt-BVO-35%m is 11.85 times that of pure monoclinic Bi VO₄,indicating that the proportion of crystalline phase,can affect the strength of the built-in electric field,which in turn affects the charge separation efficiency.Under visible light（λ≥420 nm）irradiation,the rate constants of mt-BVO-35%m samples for degrading tetracycline pollutants were 3 and 1.4 times higher than those of m-BVO and mt-BVO-3%m samples,respectively.The built-in electric field and the direct Z-type charge transfer mode of mt-BVO-35%m accelerate the migration rate of photogenerated carriers and improve the photocatalytic activity.（2）Decahedral monoclinic Bi VO₄ with highly exposed{010}facets was synthesized by facet manipulation.Fe（II）was selectively deposited on the Bi VO₄{010}crystal plane,and Fe（II）/Bi VO₄ composite photocatalysts with different loadings were designed and synthesized.By XRD,SEM and TEM characterization,the morphology and structural characteristics of Fe（II）/Bi VO₄ were analyzed,and it was found that Fe（Ⅱ）loading could expand the visible light absorption range of Bi VO₄.Under the irradiation of visible light（λ≥420 nm）,Fe（II）/Bi VO₄ was used to activate peroxymonosulfate（PMS）to improve the degradation efficiency of tetracycline pollutants.Under the conditions of 1%Fe（II）/Bi VO₄/PMS/Vis system with an initial p H of 4.17 and a PMS concentration of 0.5 m M,the degradation efficiency of tetracycline was 96.7%after 30min reaction.The control of crystal planes and the construction of heterojunctions can effectively separate the photogenerated carriers of Bi VO₄,and the cyclic transformation of Fe（II）/Fe（III）can synergize with photogenerated electrons to efficiently activate PMS and improve the degradation efficiency of pollutants.