The Preparation Of Dopamine-modified GC₃N₄ Photocatalyst And The Performance Of Its Photocatalytic Graphene Composite Film

With rapid industrial development,the amounts of various generated organic contaminants have had an influence on human habitats and are becoming serious threats to the longterm development of human society and environmental sustainability,among pollutants like insoluble oils and soluble organic dyes are hazardous for natural environment and human health.In this paper,PDA modified g-C3N4 photocatalysts is applied to degrade organic dye and investigated the mechanism of degradation.Subsequently,the g-C3N4 introduced into the graphene oxide and formed the photocatalytic membrane via filtration method.These experiments follow below:Firstly,graphitic carbon nitride sheet(g-C3N4)was prepared by the thermal treatment of melamine and polydopamine/graphitic carbon nitride(PD A/g-C3N4)was synthesized by the dopamine(DA)polymerization modification of the surface of g-C3N4.For a study of the morphology and optical property of catalysts,the obtained PDA/g-C3N4 composites were characterized by FTIR,XRD,SEM,TEM,BET,XPS,TGA,DRS(diffuse reflectance spectroscopy),photoluminescence,and photocurrent generation.Polydopamine(PDA)plays multiple roles as a light absorption substance,an electron transfer acceptor,and an adhesive interface in the design of PDA/g-C3N4 photosynthetic systems.The optical results demonstrate that PDA has an effect on the PDA/g-C3N4 composite light-harvesting capacity.With an increasing PDA ratio,the photocatalyst’s light-harvesting ability was gradually improved.Comparing with pure g-C3N4 photocatalytic,the 10%PDA/g-C3N4 composite has been shown to be highly efficient for the degradation of the organic dyes methylene blue(MB)about 98%in 180min under visible-light irradiation,and the degradation efficiency of catalysts is higher than 90%after four cycles.Polydopamine(PDA),as a surface-modified additive with abundant semiquinone and quinone functional ligands,was introduced for an improvement of the transfer ability of photoinduced electrons and accepts them from a semiconductor-based photocatalysis material(g-C3N4),which can reduce electron-hole recombination of g-C3N4 and enhance the photocatalytic activity.Secondly,the reduced graphene oxide/graphitic carbon nitride sheet(RGO/PDA/g-C3N4)was fabricated by the dopamine modification and assembling the RGO/PDA/g-C3N4 composites on the surface of commercial CA(cellulose acetate)membrane,consisting of an RGO/PDA/g-C3N4-CA composites membrane and RGO/PDA/g-C3N4 free standing membrane.These composite materials and membrane were characterized by XRD,SEM,XPS,AFM,DRS.Finally,The RGO/PDA/g-C3N4 composites membrane achieve to continuous and simultaneous flow-through separation of oil/water emulsion and degradation of soluble organic dye under visible-light irradiation in a short time.The results demonstrate that the flux of RGO/PDA/g-C3N4 composite membrane was strongly influenced by g-C3N4 ratio.With the g-C3N4 ratio increasing,the membrane flux was gradually improved,besides,the separation rate of oil/water emulsion and retention rate of MB(methylene blue)is about 99.5%and 99.8%,respectively.Most important of all,the composite membrane can keep steady flux and high separation and retention efficiency after 5 times of recycling under visible-light irradiation.The composite membrane investigated in this study hope to become an attractive way as promising candidate for water purification.