Study On The Synthesis And Performance Of Graphene Oxide Composite Nanofiltration Membrane

Membrane technology is playing an increasingly important role as a green and energy-saving high-tech industrial technology in dealing with the current water crisis and the serious environmental problems.Nanofiltration(NF)membranes have advantages of resource saving and clean production for many industrial fields,such as desalination,organic matter removal,pharmaceuticals,textiles,petrochemicals,etc.Graphene oxide(GO),as a typical two-dimensional material,is an ideal material to prepare NF membrane.At present,there have a large number of studies on the synthesis of GO,but the washing and impurity removal of GO is mostly based on laboratory scale,and the continuous washing of GO by industrialized pilot equipment have rare to be reported.Besides,the sheet structure of GO NF membrane is easily compressed or even collapsed during use,and its stability during long-term operation is poor.In order to solve the above problems,this paper uses GO,titanium dioxide(TiO2)and polyethyleneimine(PEI)as the basic components to synthesize composite GO NF membrane.The synergistic effect between materials enables GO NF composite membrane has high water flux,rejection of dye and stability performance.In addition,GO was added as an additive to the interfacial polymerization nanofiltration membrane.By optimizing the membrane production process,a polysulfone-polyamide-graphene oxide(PSU-PA-GO)composite nanofiltration membrane with excellent performance was obtained.The innovations and conclusions of this paper are as follows:(1)Use 50 nm ceramic filter tube to cross-flow washing and removing impurities of GO solution on industrial pilot equipment to achieve the purpose of continuous GO removal and concentration.(2)TiO2 nanoparticles were grown in situ on the GO sheet,and different TiO2 loadings were obtained by changing the concentration of the hydrothermal reaction solution of titanium sulfate.The influence of the change of TiO2 loading on the thickness and layer spacing of GO membrane was explored,and then the influence on pure water flux and dye rejection of GO membrane was explored,further to optimize GO NF membrane with the optimal flux and dye rejection.(3)Grafting PEI polymer molecules on the surface of GO membrane,explore the effect of different molecular weight PEI on the pure water flux and dye rejection of GO NF composite membrane.The influence of different PEI molecular weights on the surface morphology,roughness,hydrophobicity,strength and stability of the membrane was studied,therefore,to optimize the reusable high-performance GO NF composite membrane.(4)Using GO as the additive,the PSU-PA-GO NF composite membrane was prepared by the interfacial polymerization method.By optimizing process parameters such as the content of additive GO and the reaction time of the oil phase,a composite nanofiltration membrane with uniform GO loading and tightly combined polyamide(PA)layer was prepared,which provides an insight for the industrial application of GO NF membranes.