Preparation And Performance Of Visible Light Response Catalysts For Photocatalytic Degradation Of Deoxynivalenol

Vomitoxin（DON）is a water-soluble trichothecene mycotoxin produced by Fusarium,which can contaminate many grains such as wheat,barley and corn.DON could cause many adverse reactions,including dizziness,nausea and vomiting.There are many methods for reducting DON,such as physical,chemical and biological methods.However,these methods may be energy-consuming,easy to introduce secondary pollution and limited in large-scale application.Therefore,it is particularly important to develop on green,efficient and safe way for DON reduction.Nowdays,most attentions have been pay to apply the technology of photocatalysis to reduce or degrade the contaminants.The degradation of toxic organic pollutants by visible light photocatalysis has several advantages:environmental-friendly,low cost,and mild conditions.In this study,as an earth-abundant,visible light responding and nontoxic semiconductor material,α-Fe₂O₃ with different morphologies were prepared and selected as the core materials to degrade DON under visible light irradiation.This study provided a new method and scientific basis for an efficient and safe way for DON degradation.The main research contents are as follows.The dendritic-likeα-Fe₂O₃ was successfully prepared from potassium ferricyanide by a facile hydrothermal synthesis method.The reaction temperature and reaction time inα-Fe₂O₃ nanomaterials synthesis had been optimized.The structure,morphology,element composition and valence of the dendritic-likeα-Fe₂O₃ were systematically characterized by scanning electron microscopy,transmission electron microscopy,X-ray diffraction and X-ray photoelectron spectroscopy.The characterization results showed that the dendritic-likeα-Fe₂O₃ had high purity,crystallinity and uniform morphology with a length of about 2μm and a width of about 500 nm.Then,the dendritic-likeα-Fe₂O₃ and commercialα-Fe₂O₃ were used to degrade DON in aqueous solution under visible light irradiation（λ>420 nm）.It was found that dendritic-likeα-Fe₂O₃ showed superior activity for the photocatalytic degradation of DON and 90.3%DON（initial concentration of 4.0μg/mL）could be reduced in 2 h.The degradation rate of DON was only 46.7%in the presence of commercialα-Fe₂O₃.In addition,the degradation products were analyzed by HPLC-MS.Two possible degradation products,P1（m/z 209.17）and P2（m/z 227.00）were proposed.The results shown that the main toxic sites 12,13-epoxy group and hydroxyl group in DON structure were destroyed during the DON degradation.The toxicity of DON may be reduced after effective photocatalytic treatment.With FeCl₃ and NH₄H₂PO₄ as precursors,α-Fe₂O₃ hollow nanotubes were prepared by hydrothermal method at 220oC and pH 8.65.Graphene quantum dots were prepared by stripping anthracite with nitric acid and sulfuric acid.Graphene quantum dots/α-Fe₂O₃ hollow nanotubes composites were successfully prepared by water bath method.Scanning electron microscopy,transmission electron microscopy,X-ray diffraction,X-ray photoelectron spectroscopy and diffuse reflection absorption spectra were used to characterize the structure,morphology,element composition and valence of the composites.The ultraviolet-visible diffuse reflectance spectra showed that the composite presented red-shift and could absorb more visible light.The visible-light photocatalytic activity ofα-Fe₂O₃ hollow nanotubes and composites combined with different graphene quantum dots for DON,Cr（VI）and DON-Cr（VI）degradation were systematically evaluated.It was found that bothα-Fe₂O₃ hollow nanotubes and graphene quantum dots/α-Fe₂O₃ hollow nanotubes composites had the photocatalytic properties for DON and Cr（VI）degradation.The photocatalytic activity of the composites was better than that ofα-Fe₂O₃ hollow nanotubes.Compared with single pollutant,the composite exhibited enhanced visible-light photocatalytic performance in reducing DON-Cr（VI）mixed pollution.The reason was attributed to Z-scheme photocatalytic system in the composites.In the scheme photocatalytic system,the rapid separation of photogenerated carriers reduced recombination of the photogenerated electron-hole.In addition,composites with Z-scheme photocatalytic system maintained good redox capacity,and significantly improved the visible-light photocatalytic efficiency.Finally,the electron spin resonance characterizations confirmed that graphene quantum dots/α-Fe₂O₃hollow nanotube composites could effectively produce hydroxyl radicals and superoxide radicals,which could promote the activities of photocatalytic degradation.