Preparation And Removal Property For BPA Of MOF Functionalized Micro/Nano Fibers

With the rapid economic development and the acceleration of industrialization,while improving people’s life,the water environment is seriously polluted,and the removal of endocrine disruptors with great hidden dangers in the water has become a problem that needs to be solved worldwide.Adsorption and photocatalysis have become the main removal methods at present.Adsorption method is widely used in sewage treatment because of its low cost,simple operation,low energy consumption,renewability,and less secondary pollution.The photocatalytic method can completely catalyze and degrade organic pollutants in water under visible-light irradiation.The process is mild and efficient.In this study,several nanofibrous adsorbents were prepare based on an eco-friendly modified MOF material.And the materials studied in this subject provide more possibilities for water environmental treatment.The research contents and conclusions include:First,MIL-53（Al）was modified by Poloxa Mer F127,the pore was adjusted from micropore to mesoporous,and then,bacterial cellulose（BC）/MIL-53（Al）-F127 composite nanofibrous membrane was prepared by vacuum filtration method.The surface morphologies of samples were observed by SEM and EDS.FTIR,XRD,XPS and BET were conducted to analyze the structure.The absorbance of BPA was measured by UV-Vis spectrophotometer to explore the adsorption performance on BPA.The SEM results show that the nanofibrous membrane prepared by vacuum filtration still had a clear network structure,and MIL-53（Al）-F127 was uniformly distributed in the BC nanofiber membrane.In addition,after being modified by Poloxa Mer F127,the structure of MIL-53（Al）-F127 was mesoporous,and the specific surface area increased,which was beneficial to the adsorption of BPA.The adsorption performance characterization showed that the optimal p H and temperature for BPA adsorption were 6 and 40°C,respectively.And the BPA removal efficiency for the prepared nanofiber membrane reached 94%within 120 min,the equilibrium adsorption capacity was8.3 mg/g,and the fitting results of the adsorption kinetic model conformed to the pseudo-second-order kinetic curve.Besides,after five repeated cycles,the BPA removal efficiency maintained 90%.Although the BC/MIL-53（Al）-F127 nanofiber membrane has good BPA adsorption performance,it still cannot completely remove BPA.Moreover,due to the small diameter of BC fiber and large particle size of MIL-53（Al）-F127,the combination of the two materials is not strong,so that the loading rate of MIL-53（Al）-F127 is not high.Therefore,it is very important to choose an appropriate carrier to improve the removal efficiency of BPA.Secondly,regenerated cellulose（RC）was selected as the carrier of MIL-53（Al）-F127 to prepare adsorption materials.RC/MIL-53（Al）-F127 composite nanofiber membrane was obtained by the electrospinning technology and in situ-solvothermal method.The results of microscopic morphology show that MIL-53（Al）-F127 was uniformly loaded on RC nanofibers,and the loading rate was significantly increased.According to the study,the optimal p H and temperature of RC/MIL-53（Al）-F127 for BPA adsorption were 6 and 40°C,respectively.Under this condition,BPA can be almost completely removed.The equilibrium adsorption capacity of the RC/MIL-53（Al）-F127 was 36.8 mg/g,and the adsorption kinetic studies indicted that the adsorption process followed pseudo-second-order kinetic model.After 5 times of repeated use,the adsorption performance of the nanofiber membrane still maintained the original 94%.Compared with BC/MIL-53（Al）-F127 composite nanofiber membrane,this adsorbent has better BPA adsorption performance and reusability.In order to further degrade BPA in water,photocatalyst g-C₃N₄ was doped into RC/MIL-53（Al）-F127 composite nanofiber membrane.RC/MIL-53（Al）-F127/g-C₃N₄composite nanofiber membrane was prepared by in-situ solvothermal method by combining g-C₃N₄ with MIL-53（Al）-F127 and simultaneously loading RC nanofibers.SEM shows that MIL-53（Al）-F127 and g-C₃N₄ were well bonded and uniformly loaded on RC nanofibers.According to the UV-vis DRS result,compared with pure g-C₃N₄,the absorption edge of RC/MIL-53（Al）-F127/g-C₃N₄ nanofiber composite film is red shifted,and the fluorescence excitation intensity is weakened,it was indicated that recombination rate of electron and hole was reduced.Besides,it was also found that the catalytic process of BPA was an oxygen-induced free radical reaction.·OH and O₂·^-had strong oxidation ability and could oxidize BPA into CO₂,H₂O and other small molecules.Under the conditions of size 5?5 cm² and p H 6,the degradation rate of BPA reached 60.4%within 120 min,and the presence of Cr（VI）will enhance the catalytic performance of the nanofiber membrane for BPA,because Cr（VI）)would act as an e^-scavenger,reduce the recombination of e^-and h⁺and enhance its photocatalytic activity.Moreover,after five reusable cycles,it still had excellent photocatalytic activity.