| With the deteriorating water environment,the separation technology of trace natural organic pollutants(NOM)in water is an indispensable part of human sustainable development.Ultrafiltration membrane technology(UF)is a common pressure membrane separation technology for the separation of pollutants in water.At present,there are still many problems to be solved in the ultrafiltration membrane technology,including the Robeson upper limit between water flux and rejection,membrane fouling,mechanical strength and corrosion resistance.Nanocomposite membrane technology is a technology that directly or indirectly modifies membrane materials through nanomaterials.The hydrophilicity,structure and charge density of membranes can be changed by different nanomaterials.Graphene oxide(GO)is a common nanocomposite currently,which itself contains more hydrophilic groups,and the epoxy groups,hydroxyl groups and carboxyl groups on GO also make it functional.Therefore,in this study,functionalized graphene oxide(mGO)was used to modify the PVDF ultrafiltration membrane by mixed matrix nanocomposite.The purpose was to prepare a high flux and rejection rate,and the antipollution performance was better.In this study,Chitosan-modified graphene oxide(CSGO),sulfonic acid-modified graphene oxide(SGO)and chitosan-sulfonic acid co-modified graphene oxide(SCSGO)were prepared by grafting chitosan(CS)and p-aminobenzenesulfonic acid(S)onto GO.Polyvinylidene fluoride(PVDF)was used as the membrane substrate,and different mGOs were mixed into the casting solution of PVDF ultrafiltration membrane by different modification or different ratios to prepare modified ultrafiltration membrane.Unmodified GO and ultrafiltration membrane modified with CS and S were prepared for comparison.The different mass gradients of the same mGO are divided into three groups of 5 mg,10 mg and 15 mg.The proportional mixing modification is to mix CSGO and SGO together,and divide into three group(2:1,1:1 and 1:2)according to the ratio of CSGO and SGO,named C: S / 1: 2,C: S / 1:1 and C: S / 2: 1.The characterization and performance tests of different ultrafiltration membranes were carried out,and the effects of different materials on the morphology and properties of modified ultrafiltration membranes were discussed.The results show that different mGO has a significant effect on the morphology and properties of the film.The modified ultrafiltration membrane with sulfonic acid group has a smooth surface,a wide pore size distribution,and a relatively obvious finger-like pore structure;while the CS is involved in the modified ultrafiltration membrane,the surface of the support layer will be larger.The pore size and more surface porosity,the section has a distinct layered structure.S will significantly improve the hydrophilicity of the ultrafiltration membrane,while reducing the zeta potential of the membrane surface;CS can also increase the hydrophilicity of the membrane and increase the surface roughness of the membrane.The addition of GO as a carrier for S and CS can improve the overall performance of the ultrafiltration membrane.CSGO can increase the water flux.Compared with the unmodified ultrafiltration membrane,the flux can be increased by 36.32%.SGO can improve the anti-pollution performance,especially irreversible.The pollution decreased by 91.67%.The ratio of C:S/1:2 in the proportioned mixed ultrafiltration membrane has the best comprehensive performance.The flux is 1.14 times that of the unmodified ultrafiltration membrane,and the rejection rate is increased by 31.31%.The total pollution resistance decreased by 45%;SCSGO had the highest HA rejection rate,reaching 96.16%,but the membrane flux was not as good as CSGO,and the relative unmodified ultrafiltration membrane was increased by 27.62%.The comprehensive performance of the functionalized GO modified ultrafiltration membrane is improved,and the performance of the membrane obtained by different modification methods has different advantages. |
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