Preparation Of Metal-modified Graphite Carbon Nitride And Performance Exploration

Graphite carbon nitride（g-C₃N₄）is a green and environmental photocatalyst,it possesses visible light response,suitable band gap（2.7 eV）,chemical thermal stability,easy acquisition and easy modification.It is widely used in organic pollutants treatment.However,it is restrictive for graphitic carbon nitride to dispose sewage due to inherent defects such as low utilization of visible light,hole recombination,and difficulty in recycling.This article intends to use metal-doping to modify graphite carbon nitride to enhance its photocatalytic capacity.The specific content is as follows:（1）The Fe-g-C₃N₄photocatalyst was fabricated by using thermal polymerization with iron（III）nitrate nonahydrate and melamine,and it was characterized by scanning electron microscope,transmission electron microscope,X-ray diffraction,X-ray photoelectron spectroscopy,the results showed that the successful doping of iron element.The photocatalytic degradation experiment was carried out with methylene blue and visible light irradiation,and then constructed Photo-Fenton reaction system.The result shows:when the iron element doping amount was 2.7wt%,the initial concentration of MB（pH=5）was 30 mg/L,the dose of Fe-g-C₃N₄was1.4 g/L and the molar ratio of Fe:H₂O₂was 1:1000,the degradation reached 99%at 60min.The recyclability and stability of Fe-g-C₃N₄has been verified,and the reaction mechanism has also been studied.The main active roles in the photocatalytic process are·O₂^-and h⁺.（2）The Co-porous-g-C₃N₄photocatalyst was prepared by using thermal polymerization with cobalt chloride and melamine that treated with concentrated hydrochloric acid.It was characterized by transmission electron microscope,X-ray photoelectron spectroscopy,UV-Vis diffuse reflectance spectrum and Brunner-Emmet-Teller,the results showed that the morphology of g-C₃N₄was transformed into porous and the cobalt element was successfully doped.The photocatalytic degradation experiment was explored with methylene blue and visible light irradiation,and constructed Photo-Fenton-like reaction system.The result shows:when the cobalt element doping amount was 0.9 wt%,the initial concentration of MB（pH=7）was 40 mg/L,the dose of Co-porous-g-C₃N₄was 1.0 g/L and the dose of H₂O₂was 6.2 mmol/L,the degradation reached 98.3%at 90 min.The recyclability and stability of Co-porous-g-C₃N₄has been verified,and the reaction mechanism has also been studied.The main active roles in the photocatalytic process are·O₂^-.（3）The FeSe₂-g-C₃N₄photocatalyst was synthesized by using solvothermal method with FeSe₂and g-C₃N₄,and it was characterized by X-ray diffraction,scanning electron microscope,X-ray photoelectron spectroscopy and magnetization curve,the results showed that FeSe₂particles were uniformly distributed on the surface of g-C₃N₄,and the FeSe₂-g-C₃N₄photocatalyst possesses ferromagnetism.Under the condition of visible light irradiation and PDS,the photocatalytic degradation experiment was carried out with methylene blue and then constructed a photo-persulfate oxidation system.The result shows:when the FeSe₂doping amount was 15 wt%,the initial concentration of MB（pH=7）was 10 mmol/L,the dose of FeSe₂-g-C₃N₄and PDS were 0.4 g/L and medium aeration,the degradation reached93%at 30 min.The aeration device plays a role in mixing and increasing the dissolved oxygen content in the reaction system.The recyclability and stability of FeSe₂-g-C₃N₄has been verified,and the reaction mechanism has also been studied.The main active roles in the photocatalytic process are·SO₄^-.This paper uses the methods of metal doping and metal semiconductor composite to modify the graphite carbon nitride,and the ferromagnetic FeSe₂-g-C₃N₄photocatalyst was prepared by a simple solvothermal method,which solves the problems of the low utilization rate with visible light,photo-generated electron hole recombination rate is too fast,difficult to recover,poor sedimentation performance and other defects.It provides certain ideas and directions for the safe disposal and management of chemical waste.