Preparation And Desalination Performance Of Polyamide Composite Nanofiltration Membranes Modified By Porous Nanomaterials

Nanofiltration has been widely used in seawater/brackish water desalination and wastewater treatment for its low energy consumption,green and high efficiency.Interfacial polymerization method is simple and convenient,which is a common method for preparing commercial nanofiltration membranes.However,commercial polyamide composite nanofiltration membranes still have some problems that need to be solved urgently,such as low water permeability,and it is a general trend to modify them to prepare high-performance composite nanofiltration membranes.In this thesis,the traditional polyamide composite nanofiltration membranes were modified by constructing suitable porous nanomaterial interlayers,and the porous nanomaterial polyamide composite nanofiltration membranes with crumpled structure were prepared to improve the membrane permeability.The structure and properties of the as-prepared membranes were characterized,and their desalination performances were explored.The main research contents and results are as follows:(1)The UiO-66-NH2 polyamide composite nanofiltration membranes with crumpled structure were prepared by modifying the traditional polyamide composite nanofiltration membranes with the construction of UiO-66-NH2 interlayer,which had good desalination performance.The UiO-66-NH2 nanoparticles prepared by solvothermal method were filtered onto polyacrylonitrile(PAN)ultrafiltration membrane by vacuum filtration method,and then interfacial polymerization reaction was carried out to prepare the composite nanofiltration membrane.The composite nanofiltration membrane obtained by optimizing the particle size and loading of UiO-66-NH2 had a permeability of 13.6 L m-2 h-1 bar-1(increased by 58.1%)and a Na2SO4 rejection of 97.5%when filtering Na2SO4 aqueous solution.The introduction of the UiO-66-NH2 interlayer can promote the formation of crumpled structure on the surface of the composite nanofiltration membrane,reduce the thickness of the separation layer,and enhance the hydrophilicity of the membrane surface,thus improving the membrane permeability.(2)The nanoporous titanium dioxide(nTiO2)polyamide composite nanofiltration membranes with crumpled structure were prepared by modifying the traditional polyamide composite nanofiltration membranes with the construction of nTiO2 interlayer,which had good desalination performance.The nanoporous nTiO2 nanoparticles prepared by the boiling water-assisted crystallization method were filtered on the PAN substrate,and then the interfacial polymerization reaction was performed to prepare the modified nanofiltration membrane.The experimental results showed that the nTiO2 polyamide composite nanofiltration membrane prepared by optimizing the nTiO2 loading had rough crumpled structure and thinner separation layer,which was helpful to improve the membrane permeability,and the membrane had a permeability of 12.8 L m-2 h-1 bar-1 and a Na2SO4 rejection of 98.2%when filtering Na2SO4 aqueous solution.