Preparation And Performance Study Of Efficient Composite Polyamide Nanofiltration Membrane Based On Interface Layer Regulation

With the growth of population and the development of industry,the demand for water resources development,treatment and recycling is increasing.Nanofiltration technology has been applied in desalination,ion concentration and industrial wastewater treatment.As the crutial component of nanofiltration technology,nanofiltration membranes have attracted much attention for their flux and separation performance.Nanofiltration membranes are often contaminated by organic matter during the industrial applications,which affects the flux and separation performance of nanofiltration membranes,and limits the development of nanofiltration technology.In order to solve the problems of membrane fouling and flux,efficient composite nanofiltration membranes are urgently needed.Two different composite nanofiltration membranes with excellent performance are designed and prepared based on the theory of interface layer regulation.To solve the pollution problem of nanofiltration membranes,the antifouling effect of the membrane is achieved by the surface grafted zwitterionpolymer buffer layer.Sulfonic acid zwitterionic PIPBS was synthesized by in situ ring-opening reaction,and PIPBS were grafted to the surface of polyamide nanofiltration membrane by interfacial polymerization forming a hydrophilic buffer layer.And composite nanofiltration membrane PTPM with zwitterionized surface was obtained.In comparison with unmodified nanofiltration membrane PTM,the salt retention performance of zwitterionic nanofiltration membrane PTPM was stable.Additionaly,the water flux could reach 10.9 L m-2 h-1 bar-1,the flux performance was increased by 165.8%.Moreover,the retention rates of Na2SO4 and MgSO4 were 97.3%and 94.1%,respectively.In addition,when the grafting rate of PIPBS is 13.6%,the flux recovery rate of the membrane can reach 98.1%after 2.5 cycles when the antifouling test using the model protein is 13.6%.After 60 h of continuous nanofiltration cycle,the permeation flux and salt retention rate of PTPM remained stable,showing excellent long-lasting antifouling ability.In order to further improve the permeation flux of nanofiltration membranes,functionalized nanoporous materials and hydrogels were used to construct an interfacial composite active layer nanofiltration membranes.Amino functionalized modified zeolite-like imidazolate skeleton AZIF-8 was used as the inorganic nanofiltration channel.Then,it was efficiently recombined with sodium alginate(SA)covalently to form an organic-inorganic hybrid gel network,which was firmly combined to the surface of the active layer of the nanofiltration membrane to obtain the composite nanofiltration membrane SAZM.The results show that the organic-inorganic hybrid gel network constructed on the surface of the nanofiltration membrane not only enhances the hydrophilicity of the nanofiltration membrane surface,but also the porous channel provides a more convenient path for the transport of water molecules.Thus,the permeation flux of SAZM is greatly improved.When the concentration of SA is 0.5 wt%and the loading of AZIF-8 is 0.1 wt%,flux of the nanofiltration membrane can reach 16.3 L m-2 h-1 bar-1,which is 297.6%higher than that of the unmodified nanofiltration membrane NFM.In addition,the synergistic effect of the hydrogel hydrate layer network and the porous channel of AZIF-8 endow the membrane excellent antifouling properties,and the flux decreased by only 4.9%in the antifouling experiment.Meanwhile,strong combination of SA hydrogel network and AZIF-8 realize the nanofiltration membrane stable nanofiltration performance in nanofiltration tests up to 80 h.