Preparation And Application Of Graphene-based Oil-water Separation Membrane By Electrochemical Method

Nowadays,water pollution is an urgent problem to be solved,especially oily sewage,which makes a negative impact on the environment.Comparing with traditional oil-water separation methods,membrane separation technology has great advantages in the oil-water separation area due to its high efficiency,energy saving,environmental protection,etc.As we all know,the membrane separation method requires the membrane with high hydrophobicity or oleophobic,thus the special invasive materials with superhydrophobic and super-oleophilic or superhydrophilic and underwater superoleophobic properties have broad application potential in the oil-water separation area.In this paper,a simple and effective synthesis method has been proposed.By the one-step electrochemical method,the graphene is peeled off and assembled on the stainless steel mesh,then graphene oil-water separation membrane with both superhydrophobic and superoleophilic properties is successfully prepared.The effects of voltage,electrolyte,and preparation time on the preparation of composite membranes are explored,meanwhile,kerosene,rapeseed oil,toluene,soybean oil,and carbon tetrachloride oil-water mixtures are selected as simulated oily wastewater for the testing of membrane separation performance.The composite membranes have been characterized by scanning electron microscopy(SEM),energy dispersive spectroscopy(EDS),infrared spectroscopy(FT-IR),X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),surface profiler,transmission electron microscopy(TEM),Raman spectroscopy,etc.The experimental results show that after the graphene has successfully assembled on the surface of the stainless steel mesh under the action of electrostatic force,the water contact angle is increased from 76 ° for the original stainless steel mesh to 150 ° for the graphene composite membrane,and the oil contact angle is reduced from the original 37 ° to 0 ° in the air,showing superhydrophobic and superoleophilic properties.Meanwhile,the results of the oil-water separation test show that the oil-water separation efficiency of the graphene composite membrane is as high as 97%.To improve the surface roughness of the membrane for increasing the hydrophobicity of the membrane surface,thus improving the oil-water separation efficiency of the composite membrane,we have changed the electrolyte composition and introduced copper ions into the electrolyte to produce a graphene/Cu composite membrane.The effects of different copper ion concentrations and other conditions on the structure and performance of the composite membrane are explored,and the graphene/Cu composite membrane is systematically tested and characterized.The experimental results show that when copper ions are introduced into the electrolyte,the water contact angle of the composite membrane is as high as 165 °,while the oil contact angle is close to 0 ° in the air,and the oil-water separation efficiency is as high as 98.5% which is significantly higher than that of the graphene composite membrane that prepared in the previous work.At the same time,graphene oxide oil-water separation membrane with superhydrophilic and underwater superoleophobic properties was prepared by electrochemical stripping method.The graphite foil is firstly pretreated by electrochemical intercalation,and then graphene oxide is prepared and assembled on the stainless steel mesh,thereby preparing a graphene oxide composite membrane.The effects of preparation time and voltage on the structure and performance of the composite membrane are explored by scanning electron microscopy(SEM),infrared spectroscopy(FT-IR),X-ray diffraction(XRD),Raman spectroscopy,etc.The experimental results prove that the graphene oxide composite membrane shows amphiphilic properties in the air,the water contact angle is close to 0 °,and the oil contact angle is 0 °,while the oil contact angle measured underwater can be as high as 155 °,showing superhydrophilic and underwater superoleophobic properties,which also makes the oil-water separation efficiency of the membrane can be as high as 99%.The above results demonstrate that the special invasive membrane prepared in this paper has a great potentiality in the oil-water separation area,and the electrochemical process also provides a potential way to prepare other graphene-based composite materials.