Preparation Of Intelligent G-C₃N₄/Ag-Based Composite Photocatalyst And Study On Photodegradation Of Tetracycline

Recently,the heavy use of antibiotics has caused serious environmental pollution problems.For example,most of the antibiotics in pharmaceutical wastewater cannot be completely absorbed.And they could be discharge into the environment.Among the various antibiotic treatment technologies,semiconductor photocatalytic degradation technology,as an advanced oxidation technology,has been applied for treating antibiotic residues in wastewater.It is a green environmental protection technology that can effectively treat organic pollutants in the environment.g-C₃N₄,as a non-metallic covalent compound,is widely used in the field of photocatalysis.It has good properties of stable properties,non-toxicity,low cost and no secondary pollution among many photocatalytic semiconductor materials.However,g-C₃N₄ has some certain limitations,such as weak absorption of visible light,low photogenerated carrier separation efficiency,low selectivity and controllability of photocatalytic degradation.The preparation of photocatalytic material with high stability,high selectivity and intelligent responsiveness has become a hot research topic in recent years.Therefore,we researched and solved these problems in the application of g-C₃N₄-based photocatalyst through a series of methods.The details are as follows:1.A molecularly imprinted Ag/Ag₃VO₄/CN heterojunction composite photocatalyst was synthesized by the direct precipitation method and photoinitiated polymerization method.The prepared materials were tested by XPS,XRD,SEM,HRTEM,FT-IR and electrochemical tests and so on.The photocatalytic activity and selectivity of the molecularly imprinted Ag/Ag₃VO₄/CN composite photocatalyst were investigated by photocatalytic degradation tetracycline and oxytetracycline under the visible light.After the Ag/Ag₃VO₄/CN was modified by molecularly imprinted polymer,the degradation efficiency of molecularly imprinted Ag/Ag₃VO₄/CN photocatalyst was further improved and the degradation rate of tetracycline at 2 h reached 90.18%.The selectivity factor???of the molecularly imprinted Ag/Ag₃VO₄/CN photocatalyst reached 3.20 during the selective experiment,which achieved high selectivity to antibiotics during photocatalytic degradation.2.AgCl/CN composite photocatalyst was prepared by the one-step calcination method and direct precipitation method.And melamine,cyanuric acid,silver nitrate,sodium chloride and acrylic acid are used as raw materials and ethanol as solvent.Furthermore,emulsion polymerization method was used to prepare PAA@Ag/AgCl/CN photocatalyst.The materials were characterized by SEM,TEM,XRD,UV-vis DRS electrochemical tests,etc.and the properties of the catalysts were investigated by photodegrading tetracycline.When PAA modified the Ag/AgCl/CN catalyst,the degradation efficiency of PAA@Ag/AgCl/CN for tetracycline increased to 79.11%.We have confirmed that PAA@Ag/AgCl/CN achieves the intelligent responsiveness of tetracycline degradation at different pH values.In addition,·O₂^-and·OH play important roles in the process of photocatalytic degradation according to the electron spin resonance spectroscopy?ESR?and capture experiments.3.Azo@Ag/Ag₂O/CN photocatalyst was prepared with azobenzene for surface modification of Ag/Ag₂O/CN.UV-vis DRS,XRD,TEM,SEM,FT-IR,Raman,XPS and other testing methods were used to characterize the composite photocatalyst,and the photocatalytic degradation ability of tetracycline was tested under different light sources.The results show that the Azo@Ag/Ag₂O/CN photocatalyst has different photocatalytic performance under visible light and ultraviolet light.Azobenzene,showing different color characteristics,has cis-trans isomerism under different light source conditions.Using tetracycline to simulate pollutants,the photodegradation efficiency of the prepared photoresponsive composite materials under visible and ultraviolet light conditions was 87.7%and 31.5%,respectively.4.Using ammonium persulfate?APS?as the initiator,N'N-methylenebisacrylamide?MBA?as the crosslinking agent,and N-isopropylacrylamide?NIPAM?as the temperature-sensitive functional monomer PNIPAM@Ag/Ag₃PO₄/CN catalyst with sensitive response function is constructed.The composite photocatalysts were characterized by UV-vis DRS,XRD,TEM,SEM,FT-IR,EDS,XPS and other tests.The ability of PNIPAM@Ag/Ag₃VO₄/CN photocatalytic degradation of tetracycline was tested by different temperatures.The photocatalytic results showed that at high temperature?45??,the photocatalytic degradation efficiency of PNIPAM@Ag/Ag₃VO₄/CN was 56.73%.However,the degradation efficiency increased to 88.96%at low temperature?20??.