Preparation Of Hierarchical MOFs Modified Carbon-coated Nanofibers And Their Application In Antibiotic Adsorption

Electrospinning is a technology for preparing nanofibers.By applying high voltage to polymer solution or molten polymer,nanofibers with extremely high specific surface area and high flux can be prepared.In the electrospinning process,nanofibers with different sizes and shapes can be prepared by adjusting the parameters such as electric field strength,polymer concentration,injection distance and solvent evaporation rate.Therefore,electrospinning is widely used in biomedical materials,energy materials,environmental governance and other fields.In recent years,hydrothermal carbon materials have attracted extensive attention in the field of adsorption due to their abundant sources,low cost,mild reaction conditions,and environmentally friendly preparation.Different forms of hydrothermal carbon materials can be prepared by adding surfactants or introducing templates,such as nanoparticles,hollow carbon spheres,and carbon nanofibers.Among them,hydrothermal carbon electrospun nanofibers can form continuous flexible membranes,which are more suitable for practical adsorption and filtration applications.MOFs have high specific surface area and highly ordered pore structure,which make them have strong adsorption capacity.By introducing different functional groups or changing the choice of metal ions,they can also achieve various specific properties.These advantages make MOFs become a research hotspot in the field of adsorption.However,the existence of MOFs powder also limits its application.Based on the above research background,this paper proposes to combine hydrothermal carbon-coated nanofibers with MOFs materials,and prepare hydrothermal carbon-coated nanofiber materials loaded with MOFs by hydrothermal reaction in situ growth method,and systematically study their antibiotic adsorption properties.The main contents of the paper are divided into the following two parts:1.A carbon-coated polyacrylonitrile/MOF-5 composite nanofiber membrane(PAN@C/MOF-5)was prepared by combining electrospinning technology with hydrothermal reaction.After MOF-5 was in-situ grown on the surface of hydrothermal carbon nanofibers,the specific surface area of the nanofibers increased from 18.15 m~2/g to 183.77 m~2/g.The introduction of hydrothermal carbon coating layer and MOF-5increased the active adsorption sites of the fibers.This study found that PAN@C/MOF-5 composite nanofiber membrane has good adsorption performance for chlortetracycline(CTC).The adsorption process conforms to the pseudo-second-order kinetic model and the Langmuir model.The adsorption capacity is as high as 387.60mg/g,which exceeds other reported CTC adsorbents.In addition,the PAN@C/MOF-5composite nanofiber membrane has high water flux and good regeneration performance,and the removal rate remains above 86%after 5 cycles.The chemical oxygen demand(COD)test of the adsorbed CTC solution showed that the concentration decreased significantly from 156.72 mg/L to 50.39 mg/L,which was lower than the discharge standard of pharmaceutical wastewater.In summary,the results show that PAN@C/MOF-5 composite nanofiber membrane has potential application prospects in the treatment of pollutants in wastewater.2.Fe-MOFs have good chemical and thermal stable super octahedral structure,rich binding sites,low synthesis cost and simple preparation.In order to further obtain a highly stable adsorbent,PAN@C/MIL-101(Fe)composite nanofiber membrane was prepared.The adsorption of six antibiotics(tetracyclines and fluoroquinolones)by PAN@C/MIL-101(Fe)composite nanofibers was studied.It was found that the composite nanofiber membrane had a high selectivity for tetracycline(TC).The adsorption process conforms to the pseudo-second-order kinetics and Freundlich model,and the adsorption capacity is 392.64 mg/g,which exceeds many reported TC adsorbents.In addition,the composite nanofiber membrane has high water flux and good regeneration performance.After 5 cycles,the removal rate remains above 93%.After adsorption by PAN@C/MIL-101(Fe)membrane,the chemical oxygen demand(COD)concentration of TC decreased significantly from 155.55 mg/L to 51.84 mg/L,which was lower than the discharge standard of pharmaceutical wastewater.The results show that the hydrothermal carbon-coated nanofiber membrane adsorbent loaded with MIL-101(Fe)prepared in this study has broad application prospects in the actual antibiotic wastewater treatment.