Synthesis Of 0D/2Dg-C₃N₄/FeOOH Composite And Its Capacity Of Photocatalytic Degradation Of Bisphenol A

Graphite phase carbon nitride（g-C₃N₄）is sought after by many scientific research teams because of its advantages such as easy preparation,environmental protection,good electronic structure and stability of physical and chemical properties.However,due to the small specific surface area of g-C₃N₄,the utilization rate of visible light is not high,and the photo-generated electron-hole is easy to recombine,which seriously reduces its photocatalytic activity and stability.In order to improve the photocatalytic activity of g-C₃N₄,this paper uses quantum dots as a protective layer to modify its surface,and then compound it with iron oxyhydroxide to prepare zero-dimensional/two-dimensional graphite phase carbon nitride/iron oxyhydroxide（0D/2D g-C₃N₄/Fe OOH）composite,and applied to photocatalysis and photo-Fenton catalytic system to degrade bisphenol A.Through various characterization methods,the photocatalytic performance and degradation mechanism of the composite materials are discussed.The main research contents and conclusions are as follows:（1）0D/2D g-C₃N₄/Fe OOH photocatalyst was synthesized,and the crystal structure（XRD）,micro-morphology（SEM,HRTEM）,specific surface area and pore characteristics（BET）,chemical bonds and chemical valence states（XPS,FT-IR）of the composites were analyzed by various characterization methods.The results show that the composite was successfully prepared and its specific surface area increased significantly.（2）The degradation performance of 0D/2D g-C₃N₄/Fe OOH composite in the degradation of bisphenol A under visible light was systematically studied.Under visible light,after 180 min of reaction,the degradation efficiency of 0D/2D g-C₃N₄/Fe OOH-3 composite to BPA can reach 95.18%.The degradation rate of0D/2D g-C₃N₄/Fe OOH-3 to BPA is 0.01348 min^-1,which was 14.4 times of g-C₃N₄,6.8 times of g-C₃N₄/Fe OOH and 4.3 times of 0D/2D g-C₃N₄.At the same time,the influencing factors of during the photocatalytic reaction were analyzed,and the following optimal conditions were obtained:the dosage of quantum dots was 30 m L,the dosage of catalyst was 0.6 g/L,the light intensity was 500 W,and the initial concentration of BPA was 10 mg/L.After four cycles,the photocatalytic activity of0D/2D g-C₃N₄/Fe OOH-3 on BPA weakened only slightly,and the degradation efficiency remained at 75%.Free radical trapping experiments show that during the degradation of BPA,superoxide radicals（·O₂^-）play a leading role,followed by hydroxyl radicals（·OH）and holes（h⁺）.（3）The degradation performance of 0D/2D g-C₃N₄/Fe OOH composite in the degradation of bisphenol A in the photo-fenton system was studied.When the photoreaction time reaches 30 min,the light intensity is 500 W,the catalyst dosage was 0.6 g/L,and the initial concentration of BPA was 10 mg/L,in the photo-fenton system,0D/2D g-C₃N₄/Fe OOH-3 can degraded BPA completely.The influencing factors（such as p H value,H₂O₂concentration,light intensity and BPA initial concentration）on the degradation process of BPA was discussed specifically.The following optimal conditions were obtained:p H=5,the H₂O₂concentration was 2 m M,the light intensity was 500 W,and the initial concentration of BPA was 10 mg/L.After five cycles,the photocatalytic activity of 0D/2D g-C₃N₄/Fe OOH-3 on BPA was only slightly reduced,and the degradation efficiency remained at 92.3%.The degree of contribution of composite materials in the process of degrading BPA follows the following rule:·OH>·O₂^->h⁺.（4）UV-vis shows that the absorption spectrum of the composite was obviously red-shifted,the absorption wavelength shifts to a long wavelength（780 nm）,and the absorption intensity of visible light also gradually increases.The forbidden band width of 0D/2D g-C₃N₄/Fe OOH was calculated,and the energy band positions of g-C₃N₄and Fe OOH were deduced,and a Z-scheme heterojunction photocatalytic mechanism was proposed.The analysis results of electrochemical and fluorescence spectrum show that the separation efficiency of photo-generated electron-hole pairs on the surface of 0D/2D g-C₃N₄/Fe OOH composite was significantly enhanced.（5）The degradation path of BPA was speculated based on the intermediate product.The results show that the degradation of BPA is mainly divided into three steps:first,BPA is oxidized into monocyclic organic compounds;then the ring is opened to form chain hydrocarbons;and finally it is converted into CO₂and H₂O.