Study On Properties Of Modified Polyacrylonitrile Ultrafiltration Membrane

As a mild,energy saving,high efficient separation technology,Ultrafiltration membrane technology is widely used in sewage treatment,household water treatment and other fields.As inexpensive row material,Polyacrylonitrile?PAN?is restricted used in water treatment field because of its poor mechanical properties and anti-pollution properties,even though with weather resistance,chemical resistance and other excellent features.In this paper,PAN flat membranes are prepared by non-solvent phase separation method.The structure and surface properties of PAN membranes are controlled by reaction,blending and surface modification.Microscopic analysis was performed by SEM,AFM and FTIR.The performances of the flat membranes was characterized by pure water flux,rejection rate and contact angle.PAN-ETA flat membranes are prepared by PAN and ETA reaction.The effects of reac-tion temperature and PAN concentration on the structure and properties are investigated.The results show that the viscosity of the casting solution increases with the increase of the reac-tion temperature and the concentration of the polymer.The process of phase transition in the gel bath changes from the instantaneous phase transition to the delayed phase transition,the cross-section structure changes form irregular fingers to sponge-like pore structure,respec-tively.The hydrophilicity,mechanical properties and anti-fouling properties of PAN mem-branes are improved by copolymerization with ETA.When the temperature is 80 ? and the concentration of PAN is 18%,the average pore size of the membrane is 4.44 nm.The PWF of the membrane is 52.72 L·m^-2·h^-1,the rejection of PEG2w is 96.04%;The instantaneous con-tact angle is 49°,Water flux decay rate is 15%when run in 0.3 g/L BSA solution,recovery rate reaches to 90%;And the tensile strength was 5.40 MPa,elongation rate at break 87.65%.While the tensile strength of the PAN18T25 is 4.56 MPa,elongation rate at break is 26.53%.The instantaneous contact angle is 60°,water flux decay rate is 37%and recovery rate just reaches to 66%.By blending with nano-Tio₂ and oxidation of graphene?GO?prepared,PAN plat mem-branes are modified.The blending modification by inorganic particles can effectively improve the surface porosity and roughness of the membrane and also improve the hydrophilicity of the membrane.GO and nano-Tio₂ have a strong hydrophilic properties,can enrich in the sep-aration layer during the phase separation,making the membranes forming finger-like cross-section and hydrophilic surface.When the addition amount of GO was 0.06g and the blending temperature was 80 ?,the PWF is 63.69 L·m^-2·h^-1 because of the finger-like pore structure and the rejection of PEG2w was more than 90%.The flux decay rate was 11%when run in 0.3 g/L BSA solution.When the addition amount of Tio₂ is 0.3 g,the flux increases to 94.48 L m2·h^-1,but the rejection capacity decreases greatly.The flux decay rate is 13%when run in BSA solution.Finally,the surface of PAN membrane was grafted by PAM AM,and a dense layer with good hydrophilicity was formed on the surface.The grafted membranes obtain a small pore size which greatly improved the hydrophilicity and rejection ability of the membrane.The re-srults showed,the water flux was 14.86 L·m^-2·h^-1,the instantaneous contact angle was 70.5 °,lower than that of M-pure.The rejection rate of PEG2k reaches 91.37%when in the grafting condition 60? for 4 hours.