Photocatalytic Degradation Of Tetracycline By Modified Graphite Carbon Nitride(GCN)

Pharmaceutical and Personal Care Products（PPCPs）is an emerging pollutant.As a result of its widespread use,the substance has been continuously introduced into the ecological environment.Researchers have detected trace amounts antibiotic pollutants from natural water,which can cause serious harm to human health.Among them,tetracycline antibiotics are one of the PPCPs.Because they have the advantage of low price,they were widely used in livestock and poultry industry.Their usage amount accounted for more than half of the total amount of all antibiotics,and their properties are stable and easy to remain in the environment.It is difficult to achieve complete degradation in a short time.Therefore,there is an urgent need for a method that can remove tetracycline antibiotics efficiently and completely.Compared with other treatment methods,the photocatalytic method has the advantages of high catalytic efficiency,low energy consumption,strong stability,complete degradation,and no secondary pollution,and it has considerable application prospects.In this paper,non-metallic photocatalyst graphite carbon nitride（GCN）was selected as the material to degrade tetracycline,which has the advantages of visible light response,simple preparation method,low raw material price,and controllable electronic properties.But the band gap width of graphite nitride can only absorb a limited amount of visible light,At the same time,the photoelectron hole pairs are easy to compound during photocatalysis,which led to the limitation of photocatalytic efficiency.Therefore,it is necessary to modify the material to enhance its visible photocatalytic activity.Melamine was selected as the precursor of graphite carbon nitride,and various composite photocatalysts were prepared by various modification methods such as morphology control and element doping.A series of characterization methods were used to analyze the microstructure and macro characteristics of the photocatalyst.The prepared composite material was applied to the removal of tetracycline in simulated wastewater,and the removal effect was used to measure the removal effect of the prepared material on tetracycline.The following results and conclusions were reached:1.Photocatalytic degradation of tetracycline by phosphorus doped mesoporous graphite carbon nitride.--Phosphorus-doped mesoporous graphite carbon nitride（P-mp-GCN）was prepared by simply mixing melamine,melamine polyphosphate and SBA-15,and pouring,calcining and removing the template.The specific surface area of the prepared material was as high as 198.3 m²/g,which was 10.7 times that of pure graphite carbon nitride（GCN）.The high specific surface area can provide more active sites for photocatalytic reaction.The degradation performance of tetracycline under visible light was studied.During the experiment,30 mg of photocatalyst was added to a 50 m L volume of 15mg/L tetracycline solution.The removal rate of tetracycline by P-mp-GCM was 5.60 times that of GCN and 2.60 times that of mesoporous graphite carbon nitride（mp-GCN）.2.Photocatalytic degradation of tetracycline by graphite nitride loaded with nano-Fe₃O₄.--Three magnetic iron photocatalysts（Fe₃O₄/GCN）loaded with pure graphite-based carbonitride on ferric oxide（Fe₃O₄）were prepared by a two-step method.Firstly,pure graphite carbon nitride was synthesized by a simple thermal polycondensation reaction,and then magnetic composite photocatalysts were synthesized by oxidative co-precipitation method,solvothermal method,and hydrothermal method,respectively,which were denoted as Fe₃O₄-op/GCN,Fe₃O₄-st/GCN and Fe₃O₄-ht/GCN.Among the composite materials,Fe₃O₄-op/GCN-3 has the strongest magnetic properties,with a maximum magnetization（Ms）of 13.77 emu/g.The degradation performance of tetracycline under visible light was studied.During the experiment,30 mg of photocatalyst was added to a 50m L volume of 15 mg/L tetracycline solution.The photocatalytic degradation of Fe₃O₄-op/GCN-2 was the strongest 0f the prepared materials,and the removal rate of tetracycline was 2.55 times higher than that of GCN.3.Degradation of tetracycline by phosphorus doped highly effective strong magnetic core-shell graphite carbon nitride photocatalyst.--Nano-magnetic cobalt ferrite particles（CoFe₂O₄）were prepared by coprecipitation method,and then phosphorus-doped ferromagnetic core-shell graphite carbon nitride（P-CoFe₂O₄@GCN）was prepared by thermal polymerization method.Transmission electron microscopy（TEM）characterization results showed that GCN was successfully coated on magnetic particles CoFe₂O₄,and the doping of phosphorus can significantly increase the specific surface area of the photocatalyst.The specific surface area of P-CoFe₂O₄@GCN-1 can reach 36.91 m²/g,a larger specific surface area provided more active sites for photocatalytic reaction.The degradation performance of tetracycline under visible light was studied.During the experiment,30 mg of photocatalyst was added to a 50 mL volume of 15 mg/L tetracycline solution.The removal rate of tetracycline was 3.19 times that of GCN.