Preparation Of Nylon 66 Coated Polyacrylonitrile Nanofibers Membrane And Its Application In Oily Sewage Purification

In the process of petroleum mining,transportation and using,oil spills and leaks have occurred frequently,which cause the pollution of seawater and domestic water,seriously endangering the ecological environment and threating human health.The organic matters in the oil are generally difficult to degrade and extremely toxic to microorganisms and marine organisms.Therefore,the purification of oily sewage,especially the highly emulsified oil/water emulsions becomes an urgent problem that need to be solved.Conventional processing technologies such as skimmers,air flotation,centrifugation,and coarse granulation methods often suffer from low separation efficiency,high energy consumption,high cost,or secondary contamination and sometimes they even can't separate the oil/water emulsions with small particle size.Membrane separation as a newly developed technology,has been widely studied for its advantages of energy-saving,economical and environmentally friendly.The separation membrane that can be used to treat oily sewage emulsions include microfiltration?MF?,nanofiltration?NF?and ultrafiltration?UF?.However,such commercial membranes often have the problem of low permeation flux and need to apply high driving pressure,causing high energy consumption.Based on these shortcomings,this paper aims at designing and developing a new membrane by a simple preparation method,and used to separate oil-in-water emulsion only driven by its own weight.Lastly,its application performance in oily sewage emulsion was studied.Herein,by combining the electrospinning technology,dip coating process and the method of non-solvent induced phase separation,a new kind of membrane with the great properties of high porosity,superhydrophilic and underwater superoleophobic has been prepared.By using the electrospinning method,fine-diameter fibers can be obtained.and the fibers are disorderly stacked so that the fiber membrane produced with higher porosity and surface-to-volume ratio,which enable it to penetrate the liquid easily.Therefore electrospun membrane has great advantages in improving the separation flux for emulsions.A polyacrylonitrile?PAN?nanofiber membrane was prepared by electrospinning method.After combining simple dip coating process and the method of water induced phase separation,a micron-sized roughness structure composed of nylon 66?PA66?was built on the surface of the nanofiber membrane.The surface wetting properties of the fibrous membrane were converted from hydrophilic to super-hydrophilic and underwater superoleophobicity.Then hydrophilic silicon dioxide?SiO₂?nanoparticles were added to decorate the surface of the membrane to construct a micro-nano secondary roughness structure.After that,the hydrophilicity of the prepared membrane has been further improved.On the basis of testing and analysing,it was found that the concentration of nylon 66 and the content of SiO₂ nanoparticles had a crucial influence on the surface wetting properties of the nanofiber membrane.When the concentration of nylon 66 was 1 wt%,the nanofiber membrane exhibited the greatest surface hydrophilicity property,it was endowed with superhydrophilic and underwater superoleophobic.The wetting time of the prepared membrane for the water droplets in the air was 6.4 s,the underwater oleophobic contact angle was 159o.Apart from that,the membrane also showed an ultralow oil adhesion under water,its underwater oil rolling angle was only 6.7o.When 60wt%SiO₂ was added in the solution of 1 wt%PA66,A better performance membrane was obtained.Its surface wetting property was further improved.The wetting time for water droplets of as-spun fibrous membranes was shortened to 2.6 s,and the roll angle of the underwater oil was also reduced to 2.5o.Finally,the separation property of the prepared membrane has been tested.An ultrahigh permeation flux of up to 4349 L/m² h with a separation efficiency of>99.97%was obtained solely driven by gravity?¹ kPa?.In addition,the membrane also exhibited a robust reusability for long-term separation,showing its excellent performance in anti-oil fouling.Besides,it can be applied to purify various types of oil/water emulsions.All of that demonstrate its great potential for application in the purification of oily sewage.