Preparation And Separation Performance Of Graphene Oxide-based Membrane

With the development of science and technology and the continuous improvement of people's living standards,dyestuff wastewater and oil-water emulsions are being continuously discharged into the environment,which seriously endangers the health of the human body.It has become quite imperative to remove dye and separate oil-water emulsions from wastewater before their discharge into the environment.Membrane separation technology has been widely used in the treatment of dye wastewater and oil-water emulsion because of its high efficiency,low energy consumption,easy operation and low investment.As the basis of the membrane separation process,the choice of membrane material has a decisive effect on whether the membrane can be effectively separated.Graphene oxide,as the most important derivative of graphene,due to the characteristics of its sheet-like nanostructures,large specific surface area and easy modification of oxygen-containing functional groups on the surface,has been fully studied in the application of graphene oxide composites separation membranes in recent years.In order to prepare an oxidized graphene-based separation membrane with excellent stability performance,high water flux and good separation performance,three new types of graphene oxide composite separation membranes were prepared by combining graphene oxide as matrix material combined with zinc oxide nanorods,titanium dioxide nanoparticales and isostearic acid by vacuum filtration technology in present work.The characterization and analysis of the structure and morphology of the prepared membranes were detected by various characterization methods,and the stability of the prepared membrane and its separation performance for the target were discussed in detail.The detailed work was introduced as follows:?1?Low oxidation degree graphene nanosheets and zinc oxide nanorod nanocomposite?LGO-ZnO?membrane,which consists of graphene with a low degree of oxidation nanosheets and zinc oxide nanorods,was successfully prepared based on the commercial mixed cellulose membrane with a pore size of 0.22?m by simple vacuum-filtration process.The structures and surface morphology of prepared membranes were characterized by fourier infrared spectroscopy?FT-IR?,scanning electron microscopy?SEM?,transmission electron microscopy?TEM?,X-ray diffraction?XRD?,atomic force microscopy?AFM?and raman spectroscopy?Raman?.The results showed that the ZnO nanorods were successfully embedded in the membrane layer under vacuum pressure and resulted LGO-ZnO membrane presents layer-stacked structure.Stability experiments in water showed that LGO-ZnO membrane had better stability than LGO membrane.The water flux and methylene blue dye retention was tested,and showed that the membrane had excellent water flux(1313 L m^-2h^-1bar^-1)and retention of methylene blue?99.4%?.?2?Graphene oxide-titania?GO-TiO₂-PEI?composite membrane was prepared based on the commercial mixed cellulose membrane with a pore size of 0.22?m by using graphene oxide and titania nanoparticles as main membrane-forming materials with simple vacuum-filtration process.Characterization of the morphology and structure of the prepared membrane were analyzed by various methods such as FT-IR,TEM,SEM,Raman,X-ray photoelectron spectroscopy?XPS?,AFM and XRD,the results showed that the GO-TiO₂-PEI membrane had a dense layered structure.The static water contact angle test and the stability of the membrane in water showed that the membrane has good hydrophilicity and stability.The anti-fouling performance test in the present of bovine serum albumin showed that the water flux of GO-TiO₂-PEI membrane recovered 72.4%of the original figure,suggesting good antifouling performance.The water flux and the dye rejection rate of the GO-TiO₂-PEI membrane were studied.The results showed that the prepared GO-TiO₂-PEI membrane has a water flux of 48.6 L m^-22 h^-11 bar^-1,and the rejection of methylene blue,rhodamine B,methyl orange,sunset yellow,indigo red and neocarmine dyes reached 100%,99.4%,99.1%,98.4%,95.1%and 97.6%,respectively.?3?Graphene oxide-isostearic acid?GO-ISA?composite membrane were successfully prepared based on the commercial mixed cellulose membrane with a pore size of 0.22?m by vacuum filtration with graphene oxide nanoplatelets and isostearic acid as the membrane material.The characterization and analysis of the morphology and structure of GO-ISA composite membranes were characterized by FT-IR,SEM,thermogravimetric analysis?TG?,XRD,Raman and AFM.The results showed that the GO-ISA membrane was a randomly stacked thin membrane,it also had more excellent thermal stability than the granphene oxide membrane.The three-factor three-level response surface BBD experimental optimization theory was used to optimize the entrapment conditions of toluene/water emulsion.The results showed that the mass ratio of GO/ISA was 1:2,the filtrate volume was 20 mL and the membrane treatment temperature was 50°C.Under these optimal conditions,the best rejection rate of GO-ISA membrane to toluene/water emulsion was93.7%.