Preparation And Characterization Of Inorganic Doped Composite Forward Osmosis Membrane

In the forward osmosis process,internal concentration polarization and membrane surface contamination are two important factors that affect membrane flux.Modifying the performance structure of the forward osmosis membrane by blending nanomaterials is an important way to improve the membrane separation performance.The forward osmosis composite membrane is mainly composed of a porous support layer and a separation active skin layer.In addition to the skin layer,unlike other membrane separation processes,the membrane flux is also closely related to the physicochemical properties and pore structure of the porous support layer material.The reasonable incorporation of functional nanoparticles into the support layer can improve the porosity,charge density and stain resistance of the original porous layer,thereby improving the comprehensive performance of the composite membrane.In this study,we explored the blending of one-dimensional metal oxides with the casting solution,using it as a hard template to further increase the porosity of the support layer by etching to reduce the membrane structure parameters and weaken the effect of internal concentration polarization.In addition to the membrane structure,the charges from the substrate may also provide additional osmotic pressure,which also affect the concentration polarization.Doping the membrane casting solution with inorganic ion nanopowder that can release ions is a convenient and efficient method.Specifically,this article includes the following two aspects:First,the zinc oxide rods were prepared by hydrothermal method and modified with n-octadecanethiol to improve the compatibility of zinc oxide nanorods in the PES polymer matrix.By comparison,the hydrophilicity,porosity,and forward osmosis separation performance of the support layer before and after etching the zinc oxide nanorods in the substrate membrane by dilute hydrochloric acid found that the hydrophilicity of the membrane did not change,but the porosity increased,and the forward osmosis water flux is improved without sacrificing the selectivity of the composite membrane.Secondly,the modification was prepared by hydrothermal modification and span encapsulation modification.Tourmaline has the unique properties of far infrared radiation and the release of negative ions and antibacterial activity.Introducing it into the forward osmosis membrane is expected to modify the substrate membrane structure and impart antibacterial property to the membrane.The tourmaline powder was doped into the composite membrane by blending and spraying protocols,respectively.The structure and composition of tourmaline powder and membrane were characterized by XRD,Fourier infrared spectroscopy and scanning electron microscope,and the membrane permeability and antibacterial properties were analyzed.It shows that tourmaline powder improves the forward osmosis permeability of the composite membrane,meanwhile can inhibit bacterial growth of E.coli.