Construction Of Electrospinning Nanofiber Membrane Catalytic System And Its Application In Water Treatment

With the acceleration of industry and urbanization,the substandard discharge of oily wastewater,printing and dyeing wastewater and medical wastewater has caused great damage to the water environment.However,many kinds of pollutants,strong toxicity and difficult degradation of organic matter in discharged wastewater lead to incomplete sewage treatment,which threatens human health and the balance of ecosystem.Therefore,it is urgent to develop an efficient,convenient and safe advanced wastewater treatment technology.In view of the complexity of wastewater environment,the nanofiber composite membranes were prepared based on the template function of electrospinning by efficiently introduce metal organic skeleton（MOFs）catalyst with photocatalytic performance into the three-dimensional skeleton structure of functional electrospinning nanofibers via process regulation.The nanofiber membranes separation-catalysis coupling system and photoelectric co-catalysis system were constructed respectively to realize the advanced treatment of wastewater and the reusability of composite membrane materials.This work is of great practical significance for promoting ecological progress in the five-sphere integrated strategy.The details of the study are as follows:Firstly,in this study,the NH₂-MIL-88B（Fe）（NM88B）catalyst was introduced into the three-dimensional skeleton structure of hydrolyzed polyacrylonitrile（HPAN）membrane,and the NM88B@HPAN nanofiber catalytic membrane with hydrophilic and visible light response was prepared.Due to partial dissociation of protons in carboxyl functional groups,the surface of HPAN membrane presents negative charge in water,which is conducive to improving the interaction between HPAN membrane and protonated NM88B,resulting in uniform dispersion of nanoparticles on the surface of the membrane,and improving the stability of NM88B@HPAN nanofiber membrane.The nanofiber membrane showed excellent separation efficiency（up to 99%）and high permeability flux（946～6014 L/m²/h）for five different oil-water emulsions,including n-hexane water,toluene-water and kerosene water.At the same time,due to the synergistic effect of hydrophilicity and photo-Fenton activity,the membranes have a high flux recovery rate and excellent degradation ability of Rhodamine B（RhB）（90.04%）.In addition,the nanofiber catalytic membranes have good mechanical properties,and the separation efficiency can still reach 99%after 15 repeated self-cleaning processes.In order to further improve the stability of catalyst load and the synergism between catalyst and electrospinning membrane structure,the electrospinning nanofiber composite membrane NH₂-MIL-88B/PAN was prepared.Based on in-situ growth method,NM88B nanoparticles were introduced into polyacrylonitrile nanofiber membrane,which was given photo-Fenton degradation and filtration separation properties.Meanwhile,the influence of catalyst growth condition and amount on emulsion separation,dye and antibiotic catalytic degradation performance was investigated.This membrane has high degradation performance of methylene blue（MB）and erythromycin,and the degradation efficiency of MB can reach 99.6%in 80 minutes,and erythromycin can be completely degraded in 60 minutes.In addition,the membrane also has a high permeability flux and oil-water emulsion separation efficiency,and after 8cycles of emulsion separation tests,the toluene emulsion separation efficiency is still more than 97%,the polluted membrane through natural visible light irradiation,the permeability can basically recover as before,has a good self-cleaning ability.In view of micro-pollutants（such as antibiotics,etc.）existing in wastewater,this study further adopts electro-Fenton technology（advanced oxidation technology）for mineralization treatment.However,most developed cathodes do not efficiently synthesize H₂O₂ in situ by the 2e-pathway,and their durability cannot be guaranteed due to Fe²⁺leaching.To solve this problem,in this study,electrospinning cathode（MOFs（2Fe/Co）/CNF）membrane with unique photocatalytic and electrocatalytic functions was prepared by using graphene template effect,carbonization and in situ growth methods,which realized efficient degradation of antibiotics and dyes.The Fenton reaction was activated by continuous in-situ generation of H₂O₂ at the cathode surface by a 2e-reduction reaction.In addition,the MOFs（2Fe/Co）/CNF has a narrow band gap（1.32 eV）,which enhances the visible light response performance and improves the catalytic activity site of the cathode.In the photo-electro-Fenton system（PEF）,the mineralized rates of methylene blue and erythromycin reach86.5%and 90.2%within 10 min and 30 min,respectively,indicating that the prepared cathode has excellent photoelectric synergistic catalytic performance and is expected to pass through PEF highly efficient mineralized wastewater.