Photocatalytic Degradation Of Dyestuff Wastewater And Antibacterial Activity By Reducing Graphene Oxide-bismuth Vanadate

Organic dye and pathogenic bacteria pollution in water have caused huge economic and property losses in the world.Traditional biological method,physicochemical method and new advanced oxidation method have some hidden dangers such as low efficiency,high risk of secondary pollution and difficult control of environmental toxicology to remove dyestuff and pathogenic bacteria in water.However,photocatalytic technology not only has high efficiency but also energy-saving and environmental protection,and is a new water purification technology worthy of in-depth study.In this paper,photocatalysis method was used to degrade organic dyes and to remove pathogenic bacteria from the water body.As a photocatalyst,bismuth vanadate?BiVO₄?has been reported for dye degradation.However,this catalyst faced the disadvantages of low catalytic efficiency and long catalytic time.In this paper,the reduced graphene oxide-bismuth vanadate?BiVO₄-rGO?composites were synthesized by a modified hydrothermal method.The reductive graphene oxide?rGO?was used as a support carrier to reduce the agglomeration of BiVO₄ particles.At the same time,the specific surface area of the catalyst was increased.The characterization results of SEM and XRD showed that the monoclinic BiVO₄ surface successfully coupled with a layer of rGO,and the agglomeration of BiVO₄ dose reduced.Fourier transform infrared?FTIR?and XPS results showed that GO was reduced via a hydrothermal treatment,and the composites contained a large number of oxygen-containing functional groups.The results of UV-vis diffuse reflectance characterization showed that the amount of rGO affected the band gap energy of the photocatalyst.This may be the main reason for the change of photocatalytic performance.The dye removal performance of BiVO₄-rGO composites were evaluated by the degradation of malachite green?MG?and rhodamine B?RhB?under visible light irradiation and photocatalytic results showed that the BiVO₄ with rGO modification could effectively enhance the dyes removal performance.In a specific photocatalytic experiment,BiVO₄-rGO-300 could remove 99.5%MG in two hours and 99.84%RhB in four hours,which was superior to previous studies.Furthermore,application of catalyst in practical wastewater was also taken into account.MG and RhB were degraded by BiVO₄-rGO in several kinds of actual wastewater and experimental results showed that this catalyst could efficiently remove dye in actual environment.This improvement could be ascribed to the increase of special surface area,efficient charge transfer and reduction of electron-hole pair recombination with the incorporation of rGO.The influences of pH,supporting electrolyte and mechanism of the dye degradation were also investigated in details.The antibacterial properties of BiVO₄-rGO composites were evaluated by killing Escherichia coli?E.coli?and Staphylococcus aureus?S.aureus?under visible light.The results of the antibacterial experiment showed that the antibacterial performance of the BiVO₄-rGO can be effectively enhanced by using rGO as the support substrate of the BiVO₄.In a specific photocatalytic experiment,BiVO₄-rGO-300 could remove 99.9%of E.coli and 99%of S.aureus under 40min illumination.In addition,the influences of catalyst concentration,light time on the antibacterial performance and the mechanism of the antibacterial were also studied.In this paper,the photocatalytic degradation mechanism of dyestuff and antibacterial process were simply analyzed by investigating the role of photogenerated carrier in the photocatalytic procedure.It was found that the photogenerated electrons played little role and the holes played a major role in the degradation of dyes.In the antibacterial process,both holes and reactive oxygen species which produced by photogenerated electrons were indispensable parts for killing pathogenic microorganisms.