| The industrial wastewater that is generated from textiles,plastics,and food manufacturing contains various types of dyes.In order to prevent waste water from causing harm to nature and humans,the wastewater needs to be treated and recycled before it is discharged.Among the many treatment methods for industrial wastewater,membrane separation/adsorption has been widely focused by researchers due to its advantages of high energy efficiency,low cost,and easy recycling.Metal-organic framework(MOFs)have potential applications in liquid separation/adsorption,due to their regular spatial structure,adjustable pores and huge specific surface area.In order to improve the practicability of MOFs,researchers doped MOFs with polymers to prepare MOFs/polymer composite membranes,so that MOFs retain their porosity while greatly improving their processability.In addition,selecting MOFs with modifiable functional groups and post-synthetic modification(PSM)on them can further improve the compatibility between inorganic MOFs and organic polymers,and improve the performance of MOFs/polymer composite membranes.At the same time,MOFs/polymer composite membranes prepared by choosing two-dimensional MOFs with ultra-thin thickness not only have more adsorption sites,but also make membrane formation easier.In this paper,two-dimensional MOFs containing active-NH2 groups(CuBDC-NH2,H2BDC-NH2:2-Aminoterephthalic Acid)was prepared simultaneously by ultrasonic spray method and dropwise addition method.Through the characterization of the morphology and composition structure of CuBDC-NH2,it is found that the CuBDC-NH2 prepared by the two methods is between 200-400 nm in size,about 11 nm in thickness,and has the same two-dimensional crystal structure,pore size characteristics,functional group composition and thermal stability of.Then adopt the PSM strategy,through the reaction of-NH2 on CuBDC-NH2 with polyurethane oligomer obtain CuBDCNH2/polyurethane/nylon thin film nanocomposite membrane and CuBDCNH2/polyurethane mixed matrix membrane.Through the characterization of the morphology and composition structure of the two membranes,it is found that the surfaces of the two films are continuous,dense and free of any defects.The thickness of the film increases to a certain extent with the increase of the MOFs loading.At the same time,the film has both MOFs.With the crystalline structure of the polyurethane matrix,CuBDCNH2 and the polyurethane oligomer were successfully covalent connection,and the thermal stability of the film was good.Subsequently,the CuBDC-NH2/polyurethane/nylon thin film nanocomposite membrane was used to separate water-soluble dyes,which proved that the CuBDCNH2/polyurethane/nylon thin film nanocomposite membrane not only has a higher water flux,but also has a very high dye separation ability.The CuBDC-NH2/polyurethane/nylon thin film nanocomposite membrane efficiently separates single and mixed dyes with multiple charge characteristics through electrostatic interaction,van der Waals force and size repulsion effects,with a separation efficiency of up to 98%or more.In addition,by perfectly covering the two-dimensional CuBDC-NH2 with a hydrophobic polyurethane matrix,the stability of the two-dimensional CuBDC-NH2 in water is greatly improved,making it promising to be used in the field of water treatment.At the same time,CuBDCNH2/polyurethane mixed matrix membrane is used to adsorb dyes in organic solutions.Because the CuBDC-NH2/polyurethane mixed matrix membrane is stable in organic solvents,and it can achieve efficient adsorption of cationic dyes,but almost no adsorption of neutral dyes and anionic dyes Therefore,the selective adsorption of dyes with different charge characteristics is realized,and the removal rate is as high as 85%.In addition,due to the covalent connection between the MOFs and the polymer,the stability of the membrane is greatly enhanced,thereby improving its recycling performance,making it feasible for practical industrial production. |
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