Preparation Of Visible-light-driven Graphene Aerogel Based Composites And Their Photocatalytic Dye Degradation And Antibacterial Properties

In recent decades,environmental pollution and energy shortage have become increasingly prominent,especially azo dyes and pathogenic bacteria,which results in great threat to the environment and human health.Therefore,it is imperative to develop a simple,efficient and environment friendly technology to solve the above problems.Notably,photocatalysis has aroused considerable interest with its advantages?e.g.high efficiency,low cost and environment friendly?.Nonetheless,there are two inherent defects for photocatalysts including the low efficiency in sunlight utilization and the fast recombination of photogenerated electron-hole pairs.Other technical limitations in application is the difficult separation of catalyst from the slurry and the agglomeration tendency of nano-photocatalysts,which seriously restrict its practical application.Therefore,three-dimensional visible light-responsive photocatalysts have become an important research topic in photocatalysis.In this work,two kinds of visible-light responsive photocatalysts,Ag-AgBr/TiO₂/graphene aerogel?Ag-AgBr/TiO₂/GA?and Ag-AgBr/BiVO₄/GA has been fabricated successfully through a facile hydrothermal and freeze-drying treatment.Their photocatalytic activities were studied by photocatalysis degradation of methyl orange?MO?and photocatalytic disinfection of Escherichia coli and Staphylococcus aureus?E.coli and S.aureus?,and the photocatalytic mechanism were explored by a series of characterization tests.The obtained photocatalytic composite was beneficial to carrier migration,mass transport and re-utilization in the wastewater treatment in virtue of its3D macroscopically porous structure with high conductivity.Additionally,TiO₂/BiVO₄and the well-dispersed AgBr nanoparticles in GA support act as an efficient heterojunction,which significantly promotes the light absorption and charge separation efficiency.The as-prepared Ag–AgBr/TiO₂/GA and Ag-AgBr/BiVO₄/GA exhibited excellent photocatalytic activity for MO,approximately 94.57%?30 min?and 93.92%?24 min?under visible light irradiation.Moreover,after eight consecutive cycles,Ag–AgBr/TiO₂/GA and Ag-AgBr/BiVO₄/GA showed almost no change and the photocatalytic activity had no obvious decrease,whose removal rate even reached 94.06%and 91.84%,respectively.It was found that the bacteriostasis of Ag–AgBr/TiO₂/GA and Ag-AgBr/BiVO₄/GA was stronger than that of the control by the method of bacteriostasis circle,the minimum inhibitory concentration?MIC?and the minimum bactericidal concentration?MBC?.In addition,about 7 log E.coli and 3.8 log S.aureus were inactivated by Ag–AgBr/TiO₂/GA under 42 min visible light,respectively.At the same time,the inactivation rates of E.coli and S.aureus were about 6 logs and 2.9 logs respectively when Ag-AgBr/BiVO₄/GA was irradiated by visible light for 24 min.And an excellent disinfection effect on E.coli was maintained after three applications.