Fabrication Of Fibrous Graphene Oxide-PAN Nanocomposite Membrane And Its Oil-water Emulsion Separation

Membranes,which possessed small channels and big wettability difference in oil and water,were able to separate oil-water mixture under a small static differential pressure.Membranes for oil-water separation should be imminently fabricated because of the sake of water purification and recycling oil.However,there are mainly two drawbacks in traditional membranes for oil-water separation.The first one is the low porosity of membrane,which resulted in low flux.The second is the oil-fouling phenomena of membranes,which caused a quick decline in flux during oil-water separation and hindered the greater applications of membranes.And this fouling mainly resulted from the deposition or adsorption of micro-or nano-sized oil droplets on membrane surface,inside pores and pore wall.Therefore it was a challenging task to build a membrane with high-efficient and antifouling capacity.Herein,we fabricated two novel fibrous membranes using electrospinning technology and systematically analyzed their ability for oil-water separation.（1）We fabricated the polyacrylonitrile（PAN）membrane by electrospinning and it was treated with diethylenetriamine（DETA）to introduce NH₂ groups onto the fiber surface.Finally,the aminated PAN（APAN）membrane was modified with graphene oxide（GO）.The GO/APAN membranes possessed novel 3D hierarchical hybrid structure,in which the smaller GO lamellas were modified on the APAN fibers and larger GO lamellas were connected to two or more APAN fibers.These membranes were superhydrophilic and weak-oil-adhesion under water.It showed that GO/APAN membrane exhibited ultrahigh flux（¹0000 LMH）,preferable rejection ratio（>98.1%）and superior antifouling performance（>71%）in separating oil-water emulsion.Moreover,this membrane was able to treat the acidic,alkaline and salty oily wastewater,which demonstrated that it was chemically stable.（2）Polyacrylonitrile/graphene oxide（PAN@GO）composite nanofibers with spindle-knot structure had been fabricated by facile electrospinning and then hydrolyzed（H-PAN@GO）for tailoring their chemical features,and their separation performance for oil-water was evaluated.Herein,spindle-knot structures were induced by the GO sheets.It was found that H-PAN@GO with GO contents 7%（H-PAN@GO7%）membrane was superhydrophilic in air and ultralow-oil-adhesion under water.As a result,the H-PAN@GO7%membrane exhibited ultra-high flux（³500 LMH）,satisfied rejection ration（⁹9%）and outstanding flux recovery ratio（⁹9%）for separating oil-water emulsion.The surface-adhered oil droplets could directionally self-transport along spindle-knotted fiber under water,due to the difference in Laplace pressure which originates from gradient of geometry of spindle-knotted fiber,which was further demonstrated by Lattice Boltzmann method（LBM）in this paper.This finding offered a novel insight into enhancing anti-oil-fouling capacity of membrane by building hydrophilic spindle-knot on fiber.GO-induced fabrication of spindle-knotted nanofibers membrane was facile,which possessed great potential application in the field of treating oil contaminations.To sum up,we combined GO and electrospinning in this study for fabricating GO/APAN membrane and H-PAN@GO membrane which possessed good ability in separating oil-water emulsion.It is promising for practical applications in treating oil-contaminated wastewater.