Preparation And Separation Performance Of Graphene Oxide-based Composite Membrane Materials

With the development of social economy,while people's life is extremely rich,the environment pollution problems caused by development has become the focus of social attention.The direct effluent of dye,heavy metal or oil wastewater can seriously affect the ecological balance of water environment and cause death of aquatic plants or eutrophication of water.Therefore,it is urgent to find an efficient sewage treatment technology.Because of superior separation property,in this paper,preparing graphene oxide-based composite membrane materials is the key purpose.The hollow tubular material halloysite nanotubes is used as supporting material and under the reduction and adhesion of dopamine,graphene oxide and halloysite nanotubes were tightly combined.Thus,the high flux and separation composite membrane was composed.Graphite was the raw material and part of its derivative product graphene oxide blended with halloysite nanotubes at the temperature of 80?,the polydopamine/reduced graphene oxide/halloysite nanotubes(PDA/RGO/HNTs)composite material was prepared under the reduction and adhesion of dopamine.Then,part of these composite materials was vacuum filtration on the cellulose acetate(CA)membrane,constituting a PDA/RGO/HNT-CA membrane,which is the experiment membrane materials.The structural characteristics of PDA/RGO/HNTs was characterized by X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),Fourier transform infrared(FT-IR)spectroscopy,and transmission electron microscopy(TEM).In addition,scanning electron microscopy(SEM)and atomic force microscopy(AFM)were used to detect the surface morphology structure and roughness of composite membranes,respectively.A hydrophilicity experiment demonstrated that the flux of PDA/RGO/HNT membrane was dramatically improved with an increasing HNT ratio and the retention rates of Methylene Blue(MB),Congo Red(CR),Cu2+,and Cr3+were 99.72%,99.09%,99.74%and 99.01%,respectively.The separation rate of oil/water emulsion was about 99.85%for 0.15 g PDA/RGO/HNTs membrane.Comparing with none-HNTs composite membrane,the contained HNTs membrane exhibited superior long-term performance for dye and heavy metal wastewater.More importantly,the recycle and antifouling tests indicated that the HNTs-modified membrane exhibited the superior anti-fouling capacity after three cycles.With the changing of charge and the molecular structure in dye solution at different pH condition,PDA/RGO/HNTs composite membrane materials exhibited obvious difference on CR separation effect.The rejection ratio of MB still retained above 80%,however,the minimal rejection ratio of CR was below 80%with the enhancement of pH.Moreover,interference factor such as NaCl,Na2SO4 and suspended solids had some effects on PDA/RGO/HNTs membranes for intercepting dyes.As the concentration of disturbance increased,the flux of membrane decreased gradually.The influence of these three part of interference factors leaded to minimum dyes flux such as 15.7 L·m-2 h-1(MB)?24.7 L·m-2 h-1(CR);17.7 L·m-2 h-1(MB)?25.6 L·m-2 h-1(CR);19.46 L·m-2h-1(MB)and 9.3 L·m-2 h-1(CR).The retention rate of membrane material to dye was above 95%.The absorption experiment of dyes and the separation of neutral molecule glucose and oily wastewater demonstrated the separation mechanism mainly included absorption and screening.Herein,because of high flux and high anti-fouling properties,this type of membrane materials may have a good prospect of application in actual wastewater treatment.