Construction Of High Performance Composite Membrane Based 2D Hybrid Materials For Dyes/salts Separation

Two-dimensional lamellar materials such as graphene,boron nitride?BN?and molybdenum disulfide?MoS₂?have been continuously studied and explored because of their unique physicochemical properties and atomic size thickness.Composite materials based on two-dimensional lamellar materials two-dimensional composite materials enhance the performance of material itself and also achieve a comprehensive performance superior to the original constituent materials.Inspired by this idea,this paper focuses on the study of two-dimensional laminated materials combined with one-dimensional and two-dimensional materials as composite materials,and analyzes the structural properties of the materials,aiming to use the prepared composite materials on the surface of organic membranes.The composite membranes were prepared by simple dead-end filtration method in order to exert the synergistic advantage of composite material,and membranes are expected to have high flux and good dye retention properties.The main research contents of this paper are as follows:?1?The halloysite nanotubes?HNTs?were modified by sodium polystyrene sulfonate?PSS?.The modified HNTs?mHNTs?contained sulfonate group?O₂SO^-?,which could covalently bind with zinc ions,a metal ligand in two-dimensional Metal-Organic Frameworks-L?ZIF-L?nanosheets.ZIF-L nanosheets were nucleated and crystallized on the surface of mHNTs by in-situ growth method.With the growth of ZIF-L seeds,a"leaf-tube"morphology structure was formed,that is,one-dimensional and two-dimensional bonded mHNTs/ZIF-L nanocomposites.The mHNTs/ZIF-L composite membranes were prepared by loading mHNTs/ZIF-L on the pretreated surface of polyacrylonitrile?PAN?membranes by simple dead-end filtration method.The structural morphology and physicochemical properties of the prepared nanocomposites and composite membranes were characterized.The results showed that the prepared mHNTs/ZIF-L retains the morphology and thermal stability of ZIF-L.Furthermore,the specific surface area of mHNTs/ZIF-L is much higher than the sum of the specific surface area of mHNTs and ZIF-L.At the same time,mHNTs/ZIF-L composite membranes maintained high dye rejection?>99%?and low salt rejection?<30%?,while the permeation flux(146.8 L m^-2 h^-1 MPa^-1)was significantly improved.In addition,its good operational stability and excellent antimicrobial activity also made it more competitive in the field of dye wastewater treatment.?2?We use graphene oxide?GO?and covalent organic framework?COF-1?nanosheets as the combination of two-dimensional and two-dimensional materials.Through the covalent bonding of GO with the monomer of COF-1,COF-1 can crystallize on the surface of GO by in-situ,that is,two-dimensional and two-dimensional GO/COF-1 nanocomposites.This method can improve the dispersion of COF-1 and increase the interlayer spacing of the original GO.GO/COF-1 nanocomposite was supported on the surface of PAN membrane by dead-end filtration to obtain GO/COF-1 composite membranes.The GO/COF-1nanocomposites and GO/COF-1 composite membranes were characterized by a series of structural properties.The results showed that GO/COF-1 retained the crystal structure of COF-1 and increased GO lamellar spaces.The permeability of GO/COF-1 membranes was 310.9 L m^-2 h^-1 MPa^-1,and the rejection of salt ions was less than 20%.The interception of Congo red,methyl blue,reactive black,direct red and chrome black-T dyes was as high as 98%.At the same time,GO/COF-1membrane has excellent operational stability and mechanical stability.These characteristics indicate that GO/COF-1 membrane is suitable for separation of dyes/salts in dye wastewater.