Preparation Of Biologically Reduced Graphene Oxide-based Material And Its Water Treatment Performance

Graphene is a two-dimensional nanomaterial with a honeycomb lattice structure formed by a single layer of carbon atoms.It has broad application prospects due to its huge specific surface area,excellent chemical stability and structural stability.But the preparation of graphene is the bottleneck restricting its application.In the graphene preparation methods,the graphite oxide(GO)reduction method has the advantages of low cost,high yield and large-scale production,and it is a potentially effective way to mass-produce graphene.At present,the reduction of GO is mainly achieved by adding strong chemical reagents.There is an operational risk in this reduction process,the residual chemical reagents may cause the secondary pollution of the environment,and the prepared reduced graphene oxide(rGO)sheets may tend to agglomerate and stack,affecting the performance of rGO.The biological reduction method is an environmentally friendly method,but the current biological method has low reduction efficiency and harsh reaction conditions;in addition,the powdered reduced graphene oxide has nano-toxicity,and will be harmful to the human body,biological and ecological environment,and it is difficult to recycle.Therefore,the development of efficient bioreduction graphene oxide methods and the preparation of structurally stable graphene materials have become the key technologies to promote the application of graphene.In view of the above research background and existing problems,this subject used the marine bacteria Shewanella sp.CF8-6 screened by the group as a reducing agent to achieve high-efficiency reduction of GO,and prepared biologically reduced graphene oxide(BRGO)powder material with a small amount of oxygen-containing functional groups on its surface.On this basis,in order to break through the limitations of graphene application and strengthen the stability of the three-dimensional graphene structure,this study designed and prepared bioreduced graphene oxide/polyvinyl alcohol aerogel(PVA-GA).The structural morphology was characterized and analyzed,and its adsorption performance in water treatment was explored.The main research results and discussion are as follows:(1)The GO solution was prepared by the improved Hummers method and ultrasonic stripping method.The marine bacteria Shewanella sp.CF8-6 was used as the reducing agent to reduce GO in the aqueous solution to obtain the BRGO solution,which was mixed with the crosslinking agent in a certain proportion PVA mixed reaction,PVA-GA with three-dimensional porous network structure was prepared.(2)Using X-ray photoelectron spectroscopy(XPS),Fourier infrared infrared(FTIR),Raman spectroscopy(Raman),X-ray diffraction analysis(XRD),transmission electron microscope(TEM)and scanning electron microscope(SEM)to analyze chemical composition,crystal structure and surface morphology of GO,BRGO and PVA-GA.XPS,FTIR,XRD and Raman results showed that the content of CO,OH,COOH and other oxygen-containing functional groups of BRGO was reduced,the interlayer spacing is reduced(d=0.38 nm),the crystal structure was good and it had low ID/IG value(1.26).These results confirmed that CF8-6 successfully reduced GO,and the reduction process caused little damage to the GO structure;SEM and TEM images showed that the surface of BRGO was smooth,slightly wrinkled,and less sheet agglomeration.It was successfully cross-linked with PVA,forming PVA-GA with three-dimensional porous network structure.(3)The removal effects of PVA-GA as a new type of nano-scale adsorbent on harmful components in water-organic dyes(methylene blue(MB)and Congo red(CR))and heavy metal ions(Cd2+and Pb2+)were studied.The results showed that the material exhibited efficient adsorption of organic dyes and heavy metal ions.When the initial concentration of the solution was 50 mg/L,the highest adsorption rate could reach more than 95%.The equilibrium adsorption amounts of MB,CR,Cd2+and Pb2+were respectively 135.17 mg/g,134.24 mg/g,155.27 mg/g and 145.54 mg/g;it was less affected by environmental impact factors(adsorbent concentration,pH and temperature).The above results indicated that the prepared PVA-GA had a three-dimensional porous network structure,and the use of the cross-linking agent not only enhanced the structural stability of the PVA-GA,but also provided more adsorption sites,which provides advantages for the adsorption of pollutants.The use of PVA in the preparation process reduced the preparation cost,and improved its stability,recyclability and recycling,and realized the preparation of high-efficiency,energy-saving and environmentally friendly materials.