Fabrication And Performance Of High-Penetration/antifouling Polvamide Nanofiltration Membrane

With the population growth and economic development,the demand for water resources has increased dramatically.Therefore,the shortage of water resources and the pollution of water bodies have become one of the important factors restricting so-cial development.The separation process of nanofiltration was driven by pressure.The high efficiency and low energy consumption of nanofiltration membrane make it widely used in many fields.Such as seawater desalination,wastewater treatment and ion removal in the past few decades.However,nanofiltration membrane was extremely easy to be contaminated by the organics.Besides,the low flux of it reduce the separation efficiency and produce the high consumption.Therefore,membrane fouling and low flux are important factors that limit the application of nanofiltration technology.In order to improve the antifouling performance and the penetration of nanofil-tration membrane,we designed and synthesized two new types of high-performance nanofiltration membranes from two directions.One type is zwitterionic antifouling nanofiltration membrane,and the other is mixed matrix high permeation nanofiltration membrane.First,in order to improve the antifouling performance,we prepared a zwitterio-nic nanofiltration membrane.Firstly,we designed and synthesized a new type of po-lyhydroxy zwitterionby.The hydrophilicity of the novel zwitterion was highly im-proved by introduce polyhydroxyl groups.Then the primary membrane was modified by the polyhydroxyl groups and then obtained the novel zwitterionic nanofiltration membrane.The flux of the novel zwitterionic nanofiltration membrane was signifi-cantly increased,and reach to 12.59 L m-2 h-1 bar-1,which was 3 times of the original nanofiltration membrane.Besides,the salt rejection didn’t show significantly reduc-tion.At the same time,the antifouling performance of the zwitterion nanofiltration membrane has been significantly improved.The flux recovery rate can reach to 97%after 2.5 cycles of testing by using bovine serum protein solution.In addition,the na-nofiltration membrane has excellent long-term stability.Specifically,there was no obvious change about the water flux and the salt rejection during the process of con-tinuous filtration tests for 50 h.Next,to improve the permeation of the nanofiltration membrane while keeping the rejection,a new mixed matrix nanofiltration membrane was prepared using MIL-101-NH2(Cr).Firstly,the metal-organic framework material MIL-101-NH2(Cr)containing amino groups was synthesized by hydrothermal method.Then,the MIL-101-NH2 was deposited on the surface of polysulfone ultrafiltration membrane by vacuum filtration.Finally,a mixed matrix nanofiltration membrane was fabricated by interfacial polymerization.The mixed matrix nanofiltration membrane surface presented a rough mesh-like structure.The rough structure can provide additional water transmission channels.Thus,improving the permeation of nanofiltration mem-brane.When the deposition mass of MIL-101-NH2(Cr)on the membrane reached to 28.27 μg cm-2,the permeability of the prepared nanofiltration membrane was up to 19.05 L m-2 h-1 bar-1,which was 4.6 times that of the original nanofiltration membrane.When the concentration of the feed solution increased,the mixed matrix nanofiltration membrane showed more stable performance.Because the amino group of MIL-101-NH2(Cr)can participate in the interfacial polymerization.The nanofiltration membrane owned excellent long-term stability.Specifically,no obvious change can be observed about the water flux and the salt rejection during the process of conti-nuous filtration tests for 50 h.