Structural Design And Modification Of Nanofiber-based Composite Forward Osmosis Membrane

With the growth of population and environmental pollution,the demand for fresh water increases sharply.Forward osmosis（FO）membrane,compared with other types of membrane separation techniques,such as reverse osmosis and nanofiltration,has attracted more and more attention due to low energy consumption and high water recovery.FO technique is mainly used in seawater desalination,wastewater treatment,and food processing.But the challenge of concentration polarization and the lack of high performance membrane seriously hinder its’developments.Electrostatic spinning nanofibers membrane has a great prospect in reducing concentration polarization and improving performance due to their characteristic large pore size,open pore structure and interconnecting pore structure.In order to solve the problems of increasing the thickness of polyamide layer and decreasing the performance of the aqueous phase monomer penetrating into the electrostatic spinning pore during the interface polymerization progress,this topic through the electrostatic spinning hydrophobic poly（vinylidene fluoride）（PVDF）nanofibers as support layer,and then through vacuum filter different thickness graphene oxide（GO）on the surface to build GO interlayer,and then through interfacial polymerization preparing the polyamide layer.The prepared membrane was tested and characterized.Studies have shown that hydrophobic pores,large pore size,high porosity and interconnected pore structure enable water molecules to pass through quickly and improve water flux,and the GO interlayer can improve the integrity and hydrophilicity of the membrane surface,making a good reaction platform for interface polymerization and improving the permeability selectivity of the membrane.On the basis of the above study,in order to achieve accurate regulation of the GO layer spacing,oxidized multi-wall carbon nanotubes（OMWCNTs）with different contents were introduced into the interlayer.In other words,the GO/OMWCNTs interlayer was constructed by filtrating different proportions of GO and OMWCNTs on electrostatic spinning PVDF nanofiber surface,and the interlayer structure was precisely regulated by changing the content of OMWCNTs.The experimental results showed that the addition of OMWCNTs increased the layer spacing of GO,and the introduction of an interlayer reduced the thickness of the polyamide layer by 60%from 200 nm to 85 nm.The performance test of the membrane showed that when the ratio of GO to OMWCNTs was 2:1,the water flux of the membrane(305.89 L·m^-2·h^-1)reached the highest,while the reverse salt flux(0.37 g·m^-2·h^-1)reached the lowest.It has high performance compared with previous literature reports.In this study,it is feasible to improve the performance of FO membrane by building an interlayer,and it has a great development prospect,which provides reference for the subsequent development of hydrophobic membrane and nanofiber membrane.