Preparation Of Three-dimensional Graphene-based Composite Photocatalyst And Its Photodegradation And Antibacterial Properties

In recent years,with the obvious increase of sewage discharge,people pay more and more attention to water pollution problem.Especially the pathogenic bacteria and organic dyes in industrial sewage have become a huge threat to human health.Photocatalytic technology has a huge potential application as a green and clean method for bacterial decontamination and dye degradation in wastewater.Although many semiconductors have been studied to promote photocatalytic reactions,high photogenerated electron-hole pair recombination rates,poor visible light absorption,and difficulty in recycling have limited their wide application.In order to improve the photocatalytic activity of single photocatalyst and promote the practical application of photocatalytic technology in water purification,this paper will combine the structural and functional advantages of 3D macroporous graphene aerogel to effectively improve the photo-generated charge separation rate and the mass transfer efficiency of the reactants/products in the degradation and disinfection process,and effectively solve the catalyst recovery problem.（1）A novel three-dimensional（3D）porous Z-scheme silver/silver bromide/graphiticcarbonnitride@nitrogen-dopedgrapheneaerogel（Ag/Ag Br/g-C₃N₄@NGA）photocatalyst was successfully fabricated by a facile hydrothermal and freeze-drying method.The series of characterization results certifified that the obtained Ag/Ag Br/g-C₃N₄@NGA synergistically integrates the structural and functional advantages of the Ag/Ag Br species and g-C₃N₄ into the 3D macroscopic porous nitrogen-doped graphene aerogel（NGA）with high conductivity.Through the anchoring effect of chitosan（CS）on Ag+,the small particle size,high dispersion,and in-situ loading of Ag Br catalyst on NGA can be achieved,which can effectively promote the transfer of photogenerated carriers,facilitate the exposure of catalytic sites,and improve the recycling efficiency.Benefiting from a unique composition and structure,the obtained Ag/Ag Br/g-C₃N₄@NGA exhibited excellent photocatalytic degradation effificiency for methyl orange（MO）,approximately 96%after 30 min of visible-light illumination.Moreover,Ag/Ag Br/g-C₃N₄@NGA has a disinfection effect on E.coli（approximately 6log inactivation）and S.aureus（approximately 1.2 log inactivation）in 60 min of visible-light illumination,and an excellent disinfection effect on E.coli was maintained after five applications.（2）Novel Ag₂S/Ag VO₃ graphene aerogels（Ag₂S/Ag VO₃@GAs）were synthesized via an in-situ ion exchange method.The series of characterization results verified that the Ag₂S and Ag VO₃ were evenly dispersed in graphene aerogels（GAs）with a 3D porous macrostructure.Furthermore,owing to the chelation of chitosan（CS）for Ag VO₃ and the ion exchange between well-dispersed Ag VO₃ and Na₂S,the Ag₂S can in situ grow on Ag VO₃,which prevents Ag₂S and Ag VO₃ agglomeration/shedding in the photocatalytic reaction and contributes to the enhanced photocatalytic activity and cyclic stability.Benefiting from the advantages of its unique structure and function,the Ag₂S/Ag VO₃@GAs displayed the outstanding photodegradation efficiency for methyl orange（97%removal rate in 40 min）and disinfection activity for Escherichia coli（100%antibacterial efficiency in 36 min）under simulated visible light irradiation.