Study On The Preparation And Properties Of Ionic Liquid/Regenerated Keratin/Polyacrynilitrile Nanofibrous Membrane

With the fast development of productivity and the improvement of living standards,a large amount of waste textiles accumulated.Waste wool fabric is one of the most common textile wastes,the upcycle of which can alleviate the pressure on the environment.Besides,it can be transformed into valuable resources by developing potential applications,which has great research significance.Commonly used methods have the problems of complicated keratin recovery process and the inability of solvents for secondary recovery and utilization.Therefore,in this study,1-butyl-3-methylimidazole ammonium chloride([Bmim]Cl)with high boiling point and low saturated vapor pressure was used as the green solvent to dissolve the waste wool fabrics,and then directly fabricated wool keratin/ionic liquid(IL)/polyacrylonitrile(PAN)composite nanofibrous membrane with good antibacterial performance and high moisture permeability through electrospinning.First of all,pre-treatment was applied on waste wool fabrics.Under the action of sodium thiosulfate,ammonium carbonate,and sodium dodecylbenzene sulfonate,the waste wool fabric removes a large number of dyes on the surface,making the blue waste wool fabric becomes light yellow,and the K/S value changed from 4.67 to 2.72.At the same time,ethanol and acetone was used to degrease the decolorized wool fabric in a Soxhlet extractor to remove surface grease and industrial oil stains.Use an ultrasonic cell pulverizer to pulverize waste wool fabrics into loose wool fibers,which was meant to increase the contact area with the solvent during the dissolution process,and effectively improve the dissolution efficiency.By exploring the influence of the spinning voltage and spinning solution concentration on the fabrication of composite nanofibrous membrane,it was found that the low spinning voltage cannot afford enough charge repulsion to offset the surface tension,while the excessive spinning voltage will cause beading.The low concentration of the spinning solution makes the entanglement insufficient or no entanglement,and cannot effectively resist the external force to break.In all,the optimum spinning concentration of the fiber to obtain polyacrylonitrile is 12.5%,and the spinning voltage is 12 k V.By adding different concentrations of RK/IL,ionic liquid/regenerated wool/polyacrylonitrile nanofibrous membranes with different contents of 0,10%and 20%were prepared.The morphology and structure of the regenerated nanofiber membrane were characterized by Scanning Electron Microscope(SEM),Energy Dispersive Spectrometer(EDS),and Fourier Transfer Infrared Spectroscopy(FTIR).It was found that as the concentration of RK/IL solution increased,the average fiber diameter decreased from 440 nm to 180 nm,and the standard deviation decreased from 100 to 40,which indicated that the diameter of the 20%composite nanofiber membrane was the smallest with the most uniform distribution.Capillary flow pore size analysis showed that the pore size of 20%composite nanofiber membrane was mainly distributed in 0.7-0.8?m,with an average pore size of about 0.75?m,while the pore size of pure PAN nanofiber membrane was mainly distributed in 4-5?m,with an average pore size of about 5.01?m.It proved that the pore size of the composite nanofiber membrane was smaller and the distribution was more uniform,which is consistent with the diameter analysis.Because the characteristic peak of the amide I band at the position of 1600-1700 cm^-1 of the FTIR curve is very sensitive to the changes in the secondary structure of the protein,so the peak fitting was performed.The statistical results showed that the?-helical structure content of the regenerated wool has decreased from 54.38%to 23.24%,and the content of?-sheet structure decreased from34.07%to 18.54%,while the content of disordered structure increased from 11.54%to 58.21%.It is mainly because the ionic liquid destroyed the hydrogen bonds of wool molecular,which leads to the transformation of its oriented secondary structure to the random structure.At the same time,the heating process caused the breakage of wool molecular and reduced the molecular weight as a result.The antibacterial test showed that the 20%composite nanofibrous membrane had an antibacterial rate of 89.21%against Escherichia coli and 60.70%inhibition rate against Staphylococcus aureus.In addition,the regenerated wool contained in the membrane can effectively improve the hydrophilicity of the membrane.The moisture management test(MMT)compared the 20%IL/RK/PAN composite nanofibrous membrane with PAN nanofibrous membrane.The wetting time of the top and bottom surfaces reduced from 15.9 s,5.0 s to 0.3 s,respectively.And the maximum wetting radius increases from 5.0 cm,15.0 cm to 30.0 cm,while the diffusion speed increases from0.3 mm/s,1.4 mm/s to 15.0 mm/s,24.9 mm/s,showing that the hybrid nanofibrous membrane possessed a good wettability and moisture permeability.The physical properties of nanofibrous membranes were tested,and the results showed that the elongation at break of PAN,10%and 20%IL/RK/PAN composite nanofibrous membranes decreased from 150.56%to 49.19%and 21.60%.PAN is a carbon chain macromolecule with highly flexible molecular segments.The addition of imidazole-based ionic liquid increases the rigidity of the fiber and reduces the flexibility,resulting in poor elasticity.In addition,the solvent ionic liquid 1-butyl-3-methylimidazole chloride salt can be recovered by immersing the composite nanofiber membrane from ethanol,and the mass reduction of 20%of the nanofiber membrane maintained at about 18%.EDS test showed that the chlorine content of the dialyzed composite nanofibrous membranes was significantly reduced.The whole process is green and environmentally friendly,in line with the concept of sustainable development.