Construction And Adsorption Performance Of COF-TpPa-1 Composite Material For Removal Of Pollutants From Aqueous Solution

Covalent organic frameworks（COFs）are a new type of nanoporousmaterial.Because of its high specific surface area and other excellent properties,it is widely used in gas storage,catalysis,power and adsorption fields.This paper mainly studies the preparation ofδ-Mn O₂@Tp Pa-1 composite materials,Mn Fe₂O₄@Tp Pa-1composite materials and Fe₃O₄@Tp Pa-1 composite materials using COF-Tp Pa-1 as a platform.The effect of p H,ionic strength,initial concentration of the solution,adsorption time and adsorption temperature on the adsorption effect was systematically studied,and then the optimal conditions were obtained.The adsorption isotherm,adsorption kinetics and adsorption thermodynamics were further discussed,and the recycle performance of adsorbent for adsorbing pollutants is studied.δ-Mn O₂ and Tp Pa-1 were prepared by hydrothermal method andsolvothermal method respectively,and then the two materials were combined by ultrasonic breaking method to formδ-Mn O₂@Tp Pa-1 composite material.And the U（VI）adsorption experiment was performed onδ-Mn O₂ andδ-Mn O₂@Tp Pa-1.Data analysis of characterization methods such as SEM,TEM,XRD,FT-IR and XPS showed thatδ-Mn O₂ was successfully prepared,and Tp Pa-1 was also well supported on the surface ofδ-Mn O₂.The adsorption process is fitted with pseudo-first-order kinetics,pseudo-second-order kinetics,Langmuir model,and Freundlich model.The results show that the pseudo-second-order kinetics can better fit the adsorption process than the pseudo-first-order kinetics,while the Langmuir model also better than Freundlich model,At T=298K,the maximum adsorption capacities are 499.41mg/g and 1147.77 mg/g,respectively.The thermodynamic results show that the adsorption process is endothermic spontaneously.The saturated adsorbent was desorbed with 0.1 M HNO₃ solution.After four cycles of adsorption-desorption,the two adsorbents still maintained high adsorption capacity.The magnetic Mn Fe₂O₄ was prepared by the co-precipitation method,andthe Mn Fe₂O₄@Tp Pa-1 magnetic composite material was prepared by the solvothermal method.And the two prepared materials were applied to the adsorption of U（VI）and BPA in aqueous solution.SEM,TEM,XRD and FT-IR data analysis showed that Mn Fe₂O₄ was successfully prepared and Mn Fe₂O₄ was also successfully loaded on Tp Pa-1.The adsorption data show that the adsorption of U（VI）/BPA by Mn Fe₂O₄/Mn Fe₂O₄@Tp Pa-1 is more in line with pseudo-second-order kinetics,and their adsorption process is more in line with the Langmuir model.At T=298K,the maximum adsorption capacity reached U（VI）（328.32 mg/g,1177.52 mg/g）and BPA（515.03 mg/g,926.65 mg/g）,respectively.The thermodynamic results show that the adsorption process is spontaneous.The adsorbent saturated with U（VI）and the adsorbent saturated with BPA were desorbed with 0.1 M HNO₃ and ethanol solution respectively.After four cycles,the adsorbent still maintained a high adsorption rate and adsorption capacity.The magnetic Fe₃O₄@Tp Pa-1 composite material was prepared bysolvothermal method,and it was put into the adsorption of Cr（VI）and BPA.SEM,TEM,XRD and FT-IR data analysis show that Fe₃O₄ is well loaded on Tp Pa-1.The adsorption data show that the process of Fe₃O₄@Tp Pa-1 adsorption of Cr（VI）/BPA conforms to pseudo-second-order kinetics,and is also more compatible with the Langmuir model.When T=298K,the maximum adsorption capacity is 245.45 mg/g and 1220.97 mg/g.Thermodynamic data shows that the adsorption process is endothermic spontaneously.The saturated adsorbent was desorbed with 0.1 M Na OH and ethanol solution respectively.After five cycles,the adsorption capacity of Fe₃O₄@Tp Pa-1 remained at a high level.