Preparation And Properties Of Charged Nanofiltration Membrane Based On Gallic Acid

In order to improve the removal rate of drugs and personal care products（PPCPs）by nanofiltration membranes and to address the problems of membrane biological pollution,gallic acid（GA）and polyethyleneimine（PEI）were deposited on the polyacrylonitrile hydrolysis membrane（PAN-H）through surface coating method.It was a charged composite nanofiltration membrane with excellent separation and permeability.The combination of phenolic hydroxyl group of GA and silver with the complexation of PEI and silver was the reason of the successful loading of silver nanoparticles（Ag NPs）on the surface of the membrane by UV-assisted technology to prepare GA/PEI-Ag antibacterial membrane.The effects of GA concentration,PEI concentration,PEI molecular weight,reaction time of GA and PEI and Ag NO₃concentration on membrane properties were investigated.GA,PEI and GA/PEI were characterized by Fourier Transform Infrared Spectroscopy（FTIR）to explore the chemical reaction between GA and PEI.The structure and properties of the composite membrane were analyzed by atomic force microscopy（AFM）,scanning electron microscopy（SEM）,FTIR,contact angle test and zeta potential.The parameters of pure water permeability and molecular weight cut-off were studied.The desalination of the charged nanofiltration membrane and the interception effect of PPCPs were studied.The stability and antibacterial property of the silver-loaded membrane were evaluated.The optimal membrane forming conditions were:the mass fraction of GA is 0.2%,the mass fraction of PEI is 0.3%,the reaction time is 9h,the molecular weight of PEI is 1800.The pure water permeability coefficient of the GA/PEI composite membrane was determined to be74.214 L·m^-2·h^-1·MPa^-1.The molecular weight cut-off was 958 Da.The effective pore diameter was 0.69 nm,and the isoelectric point was 7.24.SEM,contact angle and AFM test results verified that the GA/PEI complex and Ag NPs had been successfully adsorbed onto the PAN-H surface,and the hydrophilicity of the composite film was improved.The roughness had increased with introducing silver.The retention order of inorganic salt of GA/PEI composite membrane was Mg Cl₂>Ca Cl₂>Mg SO₄>Na₂CO₃>Na Cl>Na₂SO₄.The removal rate of four kinds of PPCPs of ATE,CBZ,IBU and AML of GA/PEI composite membrane was 88.04,86.59,78.83 and 91.35%respectively.In addition,The static release rate and the filtration release rate of the silver-loaded membrane were the smallest when the Ag NO₃ concentration was 8 m M,indicating that the GA/PEI-Ag silver-loaded membrane prepared at this concentration was the most stable.The results of bacteriostatic experiments showed that the GA/PEI-Ag silver membrane had good antibacterial properties against Escherichia coli.