Preparation And Adsorption Properties Of Hafnium-Based MOFs Modified Nanofiber Membrane

Pharmaceutical and personal care products（PPCPs）is a type of emerging organic pollutants,such as salicylic acid（SA）,naproxen,commonly found in prescription drugs,over-the-counter drugs,perfume,shampoo,toothpaste and other necessities of life,these products after human or animal metabolism,will be discharged into the water environment,causing great harm to aquatic life and ecosystem.Over time,the long-term accumulation of PPCPs may pose potential risks to human health,such as endocrine system disorders,liver and nervous system disorders.Therefore,reducing the contamination of PPCPs in water environments is crucial for safeguarding both the environment and human health.Adsorption is one of the commonly used methods to remove PPCPs from water,which has the advantages of simple design,low cost and renewable,and has become a widely used technology in the field of sewage purification.As a kind of nanofiber material with high specific surface area and outstanding mechanical properties,electrospun nanofibers are often changed by chemical modification,functionalization or doping with other materials to improve their surface properties and selectivity,so as to be widely used in removing different types of pollutants from water.Similarly,among many adsorbent materials,metal-organic frame materials（MOFs）with excellent properties have attracted more attention of people.MOFs is a kind of material composed of metal ions and organic ligands,showing high specific surface area,porosity,controllable pore size and multi-functional characteristics,so it was widely used in the field of adsorption.Ui O-66（Hf）MOFs is one of MOFs materials with excellent chemical and mechanical stability,so it is usually used to adsorb PPCPs from water.However,almost all MOFs are granular,which is difficult to recover during adsorption,resulting in secondary pollution,which limits their large-scale application.Loading MOFs onto the surface of nanofibers with self-supporting,high specific surfaces and high porosity seems to be an effective way to solve the difficulty of recovering MOFs materials.In this paper,we combined the electrospun nanofibers with MOFs material.By introducing MOFs material on the surface of the nanofiber membrane,the specific surface area and adsorption site of nanofiber membrane were increased,and the adsorption capacity of the nanofiber membrane for salicylic acid and naproxen were increased.In this paper,the preparation method of MOFs modified nanofiber membrane and its application in the field of adsorption of PPCPs wastewater was mainly studied,which can be divided into the following two contents:1.The Ui O-66（Hf）-NH₂ nanocrystals were grown in situ on the surface of nanofiber membrane by solvothermal synthesis,and the composite nanofiber membrane（Hf PNFM）with good adsorption properties were prepared.The pseudo-second-order kinetic model and Langmuir isothermal model can better describe the adsorption process of SA on Hf PNFM,and the maximum adsorption capacity for SA was 128.21 mg/g.At the same time,Weber-Morris model shows that the rate control steps of the adsorption process of SA by Hf PNFM were film diffusion and intraparticle diffusion.The Hf PNFM showed excellent recyclability and high SA removal efficiency.After 10 adsorption/desorption cycles,the adsorption efficiency of the Hf PNFM can still reach 96.85%of the initial adsorption capacity.Moreover,the dynamic adsorption experiment also shows that the removal rate of 50 mg/L SA by Hf PNFM can reach100%,and the chemical oxygen demand（COD）concentration of SA after filtration decreases from the original 165.89 mg/L to 41.47 mg/L,which is lower than the Chinese sewage discharge standard（GB 21904-2008）.It also showed excellent resistance to ion interference.Therefore,Hf PNFM can be considered as an environmentally friendly and promising adsorbent for the removal of PPCPs from wastewater.2.Due to the synergistic effect of various metals,bimetallic MOFs tend to have higher adsorption properties.Bimetallic MOFs（Ui O-66（Hf/Zr）-NH₂）were grown in situ on the surface of electrospun nanofibers by solvothermal synthesis to prepare composite nanofiber membrane（HZPNFM）.The HZPNFM composite membrane has good flexibility and can remain intact after 50 folding and bending tests.After loading Ui O-66（Hf/Zr）-NH₂,the specific surface area of the material increased from 19.64 m²/g to 99.18 m²/g.The pseudo-second-order kinetic model and Langmuir isothermal model can better describe the adsorption process of naproxen on HZPNFM,and the maximum adsorption capacity of naproxen was 158.73 mg/g.After 5 cycles of adsorption/desorption,the adsorption efficiency of the HZPNFM can still reach 82.8%of the initial adsorption capacity,and the crystal phase and micromorphology of the HZPNFM remain intact.The dynamic adsorption experiment also showed that the removal rate of 10 mg/L naproxen by HZPNFM reached 100%.In the experiment of anti-ion interference,the influence of ions on naproxen adsorption by HZPNFM was small.All these results indicated that HZPNFM had great potential in wastewater treatment.