Preparation And Application Of PMIA/GO Compitotite Nanofiltration Membrane

Membrane separations,as an environmentally friendly technology,have been rapidly developed in different separation processes for decades.Among them,nanofiltration(NF)fills the gap between ultrafiltration(UF)and reverse osmosis(RO)with major advantages of higher flux and lower operating pressure than RO membranes and better rejections to divalent salts and lower molecular weight matters than UF membranes.Therefore,NF has a wide exploit in water purification,food industry,dye removal and desalination etc.Recently,the rapid development of nanomaterials has infiltrated several of fields including membrane separation.Due to the unique performance and nanoscale dimensions of nanomaterials,they are widely utilized in material modification and other aspects.The latest attention toward nanomaterials is paid to graphene,a single 2D carbon sheet with one-atom-layer thickness.Graphene has notably high surface area,good mechanical strength and a nearly frictionless surface.However the hydrophobic nature limits its applications in water separation membranes.Whereas,graphene oxide(GO),as a derivative of graphene which includes lots of functional groups such as hydroxyl,carbonyl,epoxy and carboxyl groups,is very hydrophilic and water molecules pass through the nano-channels formed by GO packing very fast.These properties motivate membrane researchers to incorporate GO into membranes and explore their separation performance.Poly(m-phenylene isophthalamide)/graphene oxide(PMIA/GO)composite nanofiltartion(NF)membranes were prepared via a facile phase inversion method.Structures,surface properties and hydrophilicities of the membrane were analyzed using FT-IR,XPS,AFM,SEM,water contact angle and Zeta-potential measurements.FTIR spectra indicated the existence of hydrophilic carboxylic acid and hydroxyl groups in the GO molecules.SEM pictures revealed the large and finger-like micro-voids formed in the sublayer of the NF membranes after adding GO.The zeta-potential and water contact angle results proved that PMIA/GO composite membranes had more negatively charged and greater hydrophilic surfaces.The pure water flux of the PMIA/GO(0.3wt%GO)composite membrane(125.2(L/m~2/h))was 2.6 times as high as that of the pristine PMIA NF membrane(48.3(L/m~2/h))at 0.8 MPa with slightly higher rejections to all tested dyes and better fouling resistance to bovine serum albumin(BSA).This study gave an effective method for preparing composite PMIA NF membranes with high water flux and excellent antifouling property.The feasibility for treatment of dye wastewater using a home-made hollow fiber nanofiltration membrane was investigated.The membrane was assessed for the treatment of different anionic dyes(Chromotrope,Reactive Yellow,Direct Fast Blue)under various operating conditions,such as feed concentration,pH,temperature al.The newly developed PMIA hollow fiber nanofiltration membrane exhibited excellent removal capabilities with a high rejection of greater than95%for all three dyes studied under the appropriate operation conditions,and the separation performance could keep stability during the long-time operation.Thus,the fabricated PMIA hollow fiber nanofiltration membrane has broad application prospect in the dye wastewater treatment and desalination-purification processes.