Preparation Of Superwettable Poly(arylene Ether Nitrile) Nanofiber Composite Membrane And Its Oil-water Separation Performanc

The oily wastewater discharged by industry,life and agriculture has caused serious threaten to the ecological environment and human health,which becomes an important water issue of global concern.Compared with traditional methods,membrane separation technology has been widely used in the field of oil-water separation due to its low energy consumption,high efficiency and easy operation.However,the present oily wastewater often has the characteristics of strong corrosion and high temperature.These harsh conditions place higher requirements on membrane materials,which are also the bottlenecks of membrane separation technology in the treatment of oily wastewater.Poly(arylene ether nitrile)(PEN),as a special engineering polymer with high temperature resistance and strong chemical stability,has shown promising application in the field of membrane separation technology.The preparation methods of polymer membrane materials mainly include phase transformation and electrospinning.Particularly,the polymer nanofibrous membrane prepared by electrospinning technology is favored by scientists because of its adjustable pore size,high permeability,large specific surface area,light weight and easy functionalization.In view of this,the purpose of this study is to construct PEN nanofibrous membrane via electrospinning technology,which is resistant to high temperature,strong acids and bases.On the one hand,the superhydrophilic-underwater superoleophobic PEN nanofibrous composite membrane was constructed by biomimetic method and vacuum assisted filtration technology.On the other hand,the superhydrophobicsuperoleophilic PEN nanofibrous composite membrane was constructed by commercial adhesive technology and superhydrophobic nanoparticles.These two super-wetting composite membrane materials finally provide the theoretical basis for the development and application of oily complex wastewater separation.The main contents are described as follows:(1)Firstly,the poly(arylene ether nitrile)nanofibrous mat as supporting layer was prepared by electrospinning technology,and the adhesion between fibers was improved by hot-pressing process,thereby improving the mechanical strength of nanofibrous membrane.Based on vacuum-assisted filtration technology,the halloysite nanotubes(HNTs)intercalated graphene oxide nanosheets(GO)layers self-assembled onto the surface of PEN mat.After futher surface modification by polydopamine,the superhydrophilic-underwater superoleophobic PEN/HNTs@GO-PDA nanofibrous composite membrane was constructed.The FT-IR,Raman,XPS,XRD,SEM and AFM were used to characterize and analyze the structure and morphology of PEN/HNTs@GO-PDA.The wetting property and oil-water separation efficiency of PEN/HNTs@GO-PDA were assessed by contact angle,underwater oil contact angle and TOC.The effects of temperature and pH on the stability of the composite membrane were also studied.Owing to the unique hierarchical structure,rough structure and superhydrophilic-underwater superoleophobic properties,the resulting PEN/HNTs@GO-PDA nanofibrous composite membrane showed excellent separation efficiency and significant antifouling performance for various oil-in-water emulsions,with the separation flux of above 1130.56 L/m2·h.Meanwhile,the hydrogen bonding between HNTs and GO and the cross-linking of dopamine endowed the composite membrane with high stability performance.The resulting composite membrane exhibited high separation efficiency and excellent reusability for oil-in-water emulsion including high temperatures(90℃),corrosively acidic(pH=1)and alkali(pH=14)conditions,showing wide application for cleaning and recycling water resources.(2)Secondly,inorder to obtain superhydrophobic-superoleophilic PEN nanofibrous composite membrane,the TiO2 nanoparticles were modified by organosilane perfluorooctyltriethoxysilane(P-TiO2).Owing to the-Si-O-Si-covalent bond between TiO2 and PTES molecules,the prepared superhydrophobic P-TiO2 has excellent stability.Then,the superhydrophobic P-TiO2 nanoparticles were fixed on the surface of the PEN nanofibrous membrane by the strong adhesion of commercial EVO-STIK glue,thus forming superhydrophobic-superoleophilic PEN/P-TiO2 nanofibrous composite membrane.The FT-IR,XPS,XRD and SEM were used to characterize and analyze the structure and morphology of PEN/P-TiO2 nanofibrous composite membranes.The separation efficiency and contact angle of PEN/P-TiO2 nanofibrous composite membranes were characterized by trace moisture analyzers and contact angle testers,respectively.The effects of low temperature(-5℃),high temperature(100℃),strong acid/alkali environments(pH=1 and pH=13)and ultrasonic treatment on the stability were also studied.The results showed that the PEN/P-TiO2 nanofibrous composite membrane had high separation efficiency for water-in-oil emulsions only with gravity driven.It was found that the superhydrophobic properties and micro-nano structure contributed to the excellent separation performance of PEN/P-TiO2 nanofibrous composite membranes.The separation fluxes for surfactant-free water-in-oil emulsion and surfactant-in-water emulsion reached 3351.26±231.33 L/m2·h and 6856.56±270.69 L/m2·h,respectively.In addition,the separation efficiency of them were more than 99.0%.At the same time,by using the strong adhesion of EVO-STIK glue and silicon-oxygen bonding between PTES and TiO2,the resulting PEN/P-TiO2 nanofibrous composite membrane exhibited excellent stability after treatments by ultrasonication,low/high temperature and strong acid/alkali solutions.Therefore,the superhydrophobic performance and high separation efficiency of composite membrane were maintained.