| As a new type of high efficient membrane separation technology,nanofiltration?NF?has been paid more and more attention by scholars in the field of membrane technology.But NF membrane prepared by phase inversion has the poor permeability.In order to improve the permeability and antifouling ability of nanofiltration membrane,the new nanofiltration membrane was modified and the modified nanofiltration membrane was studied systematically.In this study,poly?m-phenylene isophthalamide??PMIA?is selected as the raw materials of membrane,select the appropriate additives,and dry-jet wet spinning technology and immersion precipitation phase invention method were used to prepare f-MWCNTs/PMIA hollow fiber NF membrane and SiO2/f-MWCNTs/PMIA hollow fiber NF membrane.The results are as follows:?1?The effects of the concentration of the membrane materials,the inorganic additive?lithium chloride?,organic additive?acetone and polyvinyl pyrrolidone?,and the evaporation temperature on the structure and permeability of the prepared nanofiltration membrane were investigated.Through the study of casting solution composition and proportion and membrane preparation process,prepared nanofiltration membrane with different structures and properties,and the appropriate ratio of the dope solution was selected to provide theoretical and experimental basis for the preparation of the modified nanofiltration membrane.?2?FE-SEM,AFM,dynamic contact angle,Zeta potential and moisture meter were used to characterize the structures and properties of nanofiltration membranes modified by different types and different content of functionalized multi-walled carbon nanotubes,and the experimental results show that the blended NF membrane micro-structure changed,membrane surface roughness decreased,hydrophilic performance,surface potential and the modified membrane strength were enhanced.The experiments of pure water permeation,neutral solute and inorganic salt rejection were carried out,and the results show that the blended NF membranes with adequate addition of functionalized carbon nanotubes significantly enhanced the water flux of NF membrane,reduced membrane mean effective pore sizes,improved the rejection of inorganic salts,and the rejection to divalent ions was obviously higher than monovalent ions.When the content of carboxylic multi-walled carbon nanotubes?C-MWCNTs?was up to 0.1%,the mean effective pore diameter of the modified nanofiltration membrane was 0.681nm,and the pure water flux could reach to61.1 L/?m2·h?,and the rejection rate of sodium sulfate was about 80.7%under the pressure of 10bar.In addition,the removal of dyes by NFM-0 and NFM-2 was investigated.The results showed that the modified nanofiltration membrane had a good effect on the acid dyes,and the flux decreased significantly lower than that of the PMIA membrane.?3?The effects of different content of hydrophilic SiO2 nanoparticles added into dope solution on the structure and properties of f-MWCNTs/PMIA nanofiltration membranes were studied on.The modified nanofiltration membrane was investigated by FE-SEM,AFM,dynamic contact angle and porosity,and the results showed that the adequate addition of SiO2 nanoparticles can inhibit the formation of large pore structure,increase the membrane thickness of cortex,reduce the surface roughness,and enhance membrane surface hydrophilicity.The study on the permeability performance tested on the modified membrane find that the water flux increases with the increase of SiO2 content,while mean effective pore sizes of membrane surface decrease first and then increase,and inorganic salt rejection increase first and then decrease.?4?The anti-fouling ability of NFM-0,NFM-2 and NFM-6 were tested by bovine serum albumin solution with the concentration of 200mg/L.The experimental results show that the addition of functionalized multi-walled carbon nanotubes and hydrophilic SiO2nanoparticles can enhance the electrostatic repulsion effect between the membrane surface and BSA;enhance the hydrophilicity of membrane surface which form a layer of water to hinder the absorption of pollutants;reduce the surface roughness which reduce the pollutant blockage on the membrane surface.Thereby the modified nanofiltration membrane enhanced the pollution resistance ability,and water flux recovery rate increased from 84.8%to 97.1%and 97.5%. |
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