Preparation Of Antibacterial Ultrafiltration Membranes With Immobilizated Silver Nanoparticles

Ultrafiltration(UF)has received much attention as an effective separation process in many application fields.However,the membranes easily suffer severe biofouling,which causes irreversible decrease of membrane performmance.In order to solve this critical problem,our study attempted to prepare AgNPs-PDA/PSf membrane and PES/PANI-Ag membrane by surface modification and blending modification,respectively.Both modifications are expected to improve the anti-bacterial property as well as permeability,antifouling properties of ultrafiltration membrane.Firstly,for surface modification,silver nanoparticles(AgNPs)were in situ immobilized on commercial polysulfone(PSf)ultrafiltration membrane via polydopamine(PDA)deposition and in situ reduction of silver ammonia aqueous solution(Ag(NH3)2OH).The adhesive and reductive PDA layer existing on the membrane surface induced the reduction of Ag+ on the site of surface without surface pore blockage,and also favored to the firm attachment and uniform distribution of AgNPs onto the membrane.The diameter and density of the immobilized AgNPs were regulated by changing [Ag(NH3)2]+ ion concentration,which exerted an influence on membrane hydrophilicity and permeation flux.The prepared AgNPs-PDA/PSf membranes were characterized by X-ray photoelectron spectroscopy(XPS),scanning election microscope(SEM),atomic force microscopy(AFM),water contact angle measurement and thermogravimetric analysis(TGA).The results indicated that AgNPs were immobilized on the surface as well as the top layer cross section of the membranes.The increase of Ag+ ion concentration led to an increase in the size and density of AgNPs anchored onto the membrane.Compared with PSf membrane,AgNPs-PDA/PSf(20mM)membrane showed higher water flux,slower flux decline rate during BSA solution filtration and higher flux recovery ratio after simple water flushing.The AgNPs-PDA/PSf(20m M)membrane possessed excellent stability with little release of silver during the filtrate operation or static immersion in water for 12 days.Besides,AgNPs-PDA/PSf(20m M)membrane displayed excellent anti-bacterial and ani-biofouling properties against E.coli and B.subtilis.Then,for blending modification,polyaniline-silver(PANI-Ag)nanocomposite was first prepared with the aid of PDA layer.After that,PANI-Ag nanocomposite was blended with polyether sulfone(PES)to prepare PES/PANI-Ag composite UF membrane by phase inversion technique.The prepared PANI-Ag was characterized by ATR-FTIR,UV-vis,XRD,TEM and FE-SEM.The prepared PES/PANI-Ag membranes were characterized by ATR-FTIR,XPS,FE-SEM,water contact angle measurement and TGA.The experimental results showed that AgNPs have been evenly and firmly attached onto PANI nanofibers with the aid of PDA,with the average diameter of AgNPs being 30 nm.After blending modification,PANI-Ag nanocomposite could be stayed evenly and stably in the matrix of PES membrane.Compared with the unmodified membrane,modified membranes displayed a better performance with higher permeability,excellent antifouling and anti-bacterial properties.