Photocatalysis-persulfate Degradation Of Sulfamerazine Via Novel Carbon-nitrogen Composites

Photocatalysis is a promising technology to solve some severe global issues such as energy shortage and environmental pollution.Enhancing the utilization of solar light is a focus in photocatalusis research.Applying a suitable long-wave-light（1000-2500 nm）absorber,which can generate photothermal effect,is a prospective choice to promote photocatalytic activity and solar utilization.Carbonaceous materials are considered to be valuable photothermal agents because of their excellent solar light absorption capability.Graphitic carbon nitride（CN）is an ideal semiconductor owing to its low cost and visible light response.Therefore,activated carbon（AC）,a common material applied in pollution treatments,was selected to modify graphitic carbon nitride to obtain light absorber/semiconductor composites in this thesis.The photocatalytic activity and solar energy utilization of the synthesized materials in the process of degrading sulfamerazine（SMR）were investigated.The critical results are as follows:（1）Carbon-doped graphitic carbon nitride（x ACCN）were prepared by polycondensation method using melamine as the precursor of g-C₃N₄.The results of XRD,SEM and FT-IR show that the composite maintained the amorphous properties of AC,the C-N framework and graphene-like layer-by layer structure of g-C₃N₄.Compared with CN,UV-Vis-NIR results show that the composites greatly enhances the absorption of visible light and near-infrared light,and the total utilization rate of sunlight reaches 87.7%.XPS and PL results clarify that the band structure of g-C₃N₄ is optimized and the interfacial charge transfer is promoted.（2）Under simulated sunlight irradiation,the degradation performance of the composites toward SMR is better than that of g-C₃N₄.Without temperature control,the degradation rate of all the materials toward SMR is higher than the temperature is controlled at 15℃.The increase in system temperature is positively correlated with the content of AC in the composite materials,indicating that the photothermal effect of AC is crucial to promoting SMR degradation.The weaker emission peak of the PL spectrum for CN at 60℃compared with that at 15℃,further indicates that photothermal effect also facilitates charge transfer and separation of electron-hole pairs.The difference in the distribution of electron density between SMR/CN and SMR/0.2ACCN calculated by DFT method further confirms the enhanced charge transfer of composites.After four cycles,the degradation efficiency of0.2ACCN toward SMR is almost the same as the fresh one,showing the excellent chemical stability of the photocatalyst.（3）The addition of persulfate（PDS）improves the degradation of SMR for both CN and the composites.Inorganic anions(Cl^-,CO₃^2-,SO₄^2-)and humic aicd（HA）in water have little effect on the degradation of SMR.The experiments of active material capture prove that·O₂^-and h⁺are the main active species in SMR degradation by photocatalysis or photocatalysis/PDS.·OH、SO₄^-·and ¹O₂ also make a small contribution to SMR degradation.This kind of composite photocatalysts which can improve the utilization of solar light（>80%）and enhance the degradation of SMR by photocatalysis or photocatalysis/PDS has a promising practical prospect.