Preparation Of Nanocarbon Composite Nanofiltration Membranes By Layer-by-layer Andtheir Seawater Sofetening Properties

Nanofiltration?NF?membrane separation technology is a simple and effective method for seawater softening.In recent years,carbon materials have received extensive attention due to its unique structure,excellent mechanical and electrical properties.Graphene oxide and carbon nanotubes have a broad application in the field of membrane separation.In this paper,graphene oxide and carbon nanotube composite nanofiltration membranes were prepared,and their properties of monovalent selectivity,hydrophilic and antifouling were tested.Firstly,graphite oxide was prepared by modified Hummers method with natural graphite as raw material,and then graphene oxide was obtained by ultrasonic dispersion treatment.The prepared graphene oxide was characterized by means of X-ray diffraetion?XRD?,Fourier IR spectra?FTIR?,UV-Vis and so on.PEI and PAA were selected to prepare the multilayer graphene oxide and polyelectrolyte composite nanofiltration membranes with a hydrolyzed polyacrylonitrile?PAN?ultrafiltration membrane as support.The monovalent separating properties of composite membrane fabricated with GO in PEI and in PAA were compared.The results show that the selectivity of the PEI/PAA-GO composite membrane was 1.6 times higher than that of the multilayer membrane without GO.While with GO mixed with PEI before layer-by-layer assembly,the prepared membrane showed selectivity 2.93 times higher than the multilayer membranes without GO.The surface morphology and chemical structure of the composite membranes were characterized by SEM,contact angles,UV-vis and FT-IR.The effects of GO concentration,number of layers and other membrane preparation conditions on the performance of composite membranes were investigated.In addition,carbon nanotube/polyelectrolyte composite membranes were fabricated by Layer-by-layer self-assembly technique.The performance of composite membranes prepared with different GO addition method was compared.Layer-by-layer assembly with pressure improved the MgCl₂ rejection,and rinsing with pressure enhanced the flux of the composite membrane.