Construction Of Imprinted Defect UiO-66 And Synergistic Adsorption Of Diclofenac Sodium And Copper Ions

As a classic pharmaceutical,nonsteroidal anti-inflammatory drug（NSAIDs）are widely used to treat the symptoms of inflammation and fever.During the production and usage of NSAIDs,it can easily enter in the water stream through a variety of ways and remain in the water for a longer duration of time.The continuous intake of water containing this kind of drugs can contribute to organ damage and metabolic disorder.Because of its electron-rich structure,NSAIDs can combine with heavy metal ions（one of the common contaminants in water）to form complex type of pollutants that can cause serious pollution and the risk of ecological imbalance even at low concentrations.Therefore,efficient and deep purification of wastewater with coexisting drugs and heavy metal ion has become a serious problem in the field of contaminants purification.For the removal of low concentrations of pollutants,adsorption method is considered to be an effective method credited to its fast pollutant removal kinetics,its ability to preserve effluent quality,and simple adsorbent preparation.The metal organic framework（MOFs）used in this paper is a new type of porous adsorption material,its porous structure and high specific surface area allows it to be widely used in the field of adsorption.However,it is difficult for MOFs to efficiently adsorb multiple pollutants at the same time,and the competition between different pollutants for adsorption sites will also lead to a decrease in adsorption capacity and adsorption rate,which makes it difficult for MOFs to efficiently and deeply purify wastewater containing multiple pollutants.To solve this problem,we proposed a novel"imprinted defect Zr-based MOF（UiO-66）"strategy for the removal of coexisting diclofenac sodium（DCF）and copper ion（Cu（II））target pollutants.The enhance the efficient and cooperative adsorption of DCF and Cu（II）by forming unique three-dimensional imprinted large pores with multiple adsorption sites.The main tasks are as follows:（1）The construction of molecular imprinting defect UiO-66s and study on its synergistic adsorption properties for DCF and Cu（II）:Nonsteroidal anti-inflammatory drugs ibuprofen（IBU）,diclofenac（DCF）and naproxen（NAP）,with identical structure like diclofenac sodium were used as imprinted ligands for the preparation of three imprinted defect UiO-66s adsorbents i.e.UiO-66@IBU、UiO-66@DCF and UiO-66@NAP.The morphology,crystal structure,pore structure,surface chemical properties,and thermal stability of the adsorbent were characterized by scanning electron microscopy（SEM）,powder X ray diffraction（PXRD）,Fourier infrared spectroscopy（FITR）,N₂ isothermal adsorption and desorption,thermogravimetric analysis（TGA）,X-ray photoelectron spectroscopy（XPS）,and hydrogen nuclear magnetic resonance spectroscopy（¹ H NMR）.The characterization results showed that the molecular imprinted UiO-66s possessed a smaller particle size and the Zeta potential value of the particle surface was increased compared to the UiO-66.The molecular imprinted UiO-66s formed19?of defective pores and exhibited a higher specific surface area and total pore volume.The mesoporous pore volume ratio of the imprinted UiO-66s was also increased,and the highest V_Meso/V_Micro ratio was 3.0 times that of UiO-66.A The adsorption results showed that the adsorption capacity of UiO-66@NAP for DCF and Cu（II）was 3.5 times（385 mg/g）and 1.7 times（52 mg/g）compared to that of UiO-66,respectively.The adsorption capacity of UiO-66@NAP for DCF in the binary system was 1.4 times（573 mg/g）of the single system;The adsorption capacity of Cu（II）in the binary system was 2.6 times（135 mg/g）higher than the single system.In addition,combined with sequential adsorption experiments and changes in FITR and XPS characterization before and after adsorbent adsorption,it was concluded that there was bridging between DCF and Cu（II）components on the adsorbent surface.The accumulation of the adsorbate on the surface of the adsorbent can be used as adsorption sites for another component adsorbate.As a consequence,the formation of the surface-MOF-DCF-Cu（II）or-MOF-Cu（II）-DCF ternary complex on the adsorbent resulted in the coordination of the two-component adsorption.（2）The construction of ion-imprinted UiO-66s with polyhydroxy adsorption sites and study on the enhancement of DCF and Cu（II）synergistic adsorption:Based on the bridging synergy between the two components of DCF and Cu（II）,in order to enhance the adsorption capacity of the adsorbent towards DCF and Cu（II）and to achieve enhanced synergistic adsorption of DCF and Cu（II）two components,the imprinted defect UiO-66s adsorbent was modified by“hydroxy-ligand doping and ionic imprinting co-modification strategy”.Using copper ion as an imprinted ion and dihydroxybenzoic acid as a hydroxyl ligand,a multistage pores ionic imprinted UiO(Zr/Cu_10%)_A-DBA adsorbent with multiple adsorption sites was prepared.The SEM,EDS,PXRD,FITR,TGA,XPS and ¹H NMR were used to analyze the effects of the introduction of hydroxyl ligands and imprinted ions on the crystal morphology,pore structure and surface chemical properties of the adsorbent.The characterization findings suggested that UiO(Zr/Cu_10%)_A-DBA had smaller particle size and lattice shrinkage compared to UiO-66,and EDS analysis proved that copper metal source was successfully introduced into the UiO-66structure.The copper imprinted pore can be partially removed after a deformable process.UiO(Zr/Cu_10%)_A-DBA formed the defect pores with the size of 20.1?.Similarly,the ratio of total pore volume and mesopore volume was increased and the V_Meso/V_Micro ratio was 4.9 times higher than that of UiO-66.After the introduction of hydroxyl ligands and imprinted ions,the amount of hydroxyl sites increased with a strong adsorption capacity in the adsorbent structure,and the number of hydroxyl sites in UiO(Zr/Cu_10%)_A-DBA was 2.4 times that of UiO-66.The adsorption results revealed that the adsorption capacity of UiO(Zr/Cu_10%)_A-DBA for DCF and Cu（II）single components was 4.5 times（475 mg/g）and 2.8times（66 mg/g）that of UiO-66.For two components system,UiO(Zr/Cu_10%)_A-DBA showed enhanced synergistic adsorption of DCF and Cu（II）revealed that the adsorption capacity for DCF and Cu（II）in two components systems was 1.3times（757 mg/g）and 1.2 times（164 mg/g）times,respectively compared to that of UiO-66@NAP.The Langmuir constant value（K_L）of UiO(Zr/Cu_10%)_A-DBA for DCF and Cu（II）was 1.8 times and 2.4 times higher than UiO-66@NAP,respectively.The results indicated that the adsorption affinity and synergistic adsorption ability of adsorbent to DCF and Cu（II）can be effectively improved by applying“hydroxyl ligand doping and ion imprinted co-modification”strategy.