Preparation And Properties Of Sodium Alginate-based Hierarchical Nanofiber Membrane

Nowadays,the pollution situation in society is becoming increasingly severe,and the water resources and atmosphere on Earth have been severely damaged.It has become a major factor restricting social development and technological progress.Therefore,it is urgent to address the issues of air and water pollution.Traditional membrane separation materials play an important role in air filtration and water oil separation,but there are still problems such as low filtration accuracy and difficulty in achieving high efficiency and low resistance.Electrospun nanofiber materials have the advantages of small fiber diameter,large specific surface area,small pore size,high porosity,and good connectivity of internal pores in fiber membranes,playing an important role in various application scenarios such as air and water treatment.Sodium alginate（SA）,as a natural biomaterial derived from algae,has been widely concerned in laboratory and industrial applications due to its biocompatibility,biodegradability,processability and low cost.In this study,electrospinning technology was used to investigate the effects of experimental parameters such as solute concentration and solvent ratio on the morphology of nanofibers.The optimal electrospinning process parameters were obtained by combining rheological and SEM characterization techniques.SA nanofiber membranes with bead like structures were prepared,and their applications in air filtration were explored.The filtration efficiency of the dense SA nanofiber membrane is over 99%,but the resistance pressure drop can reach up to 330 Pa.The filtration efficiency of the beaded SA nanofiber membrane decreases with the decrease of the aerosol particles,but the resistance pressure drop of the beaded nanofiber membrane also decreases significantly.The resistance pressure drop of the nanofiber membrane prepared with the concentration of the spinning solution of 2.6%is about 100 Pa,and the quality factor is 0.0284 Pa^-1.At this time,its gas filtration effect is the most ideal.Based on the surface wettability modification method of electrostatic spinning and electrospraying,on the basis of SA nanofiber membrane,a layer of Zn O/SA functional thin layer was coated by electrospraying technology,and a micro sphere layer/nanofiber composite membrane with super hydrophilic underwater super oil repellent performance was prepared.Explored the influence of Zn O/SA concentration on the morphology and structure of the microsphere layer.The effects of Zn O particles on the pore size,surface roughness,and selected wettability of composite fiber membranes were analyzed.The highly hydrophilic polymer body,high porosity skin,and rough structure form a stable hydration layer on the membrane surface,effectively reducing the contact area between oil droplets and the membrane body,and demonstrating excellent anti-pollution performance.The experiment of oily sewage proves that the composite membrane could not only separate oil-water mixture,but also been used for the separation of oil-water emulsion.The flow rate of separation is up to 800 L·m^-2·h^-1,and it shows good circulation performance.In addition,the addition of Zn O improves the antibacterial effect of composite nanofiber membranes,resulting in multifunctional nanofiber membranes.