The Influence Of Porous Support Layer On The Structure And Performance Of Reverse Osmosis Membrane

In this study,effects of solvent selection(DMF、DMAc、NMP)、different polymer polysulfone(PSf)/ sulfonated polysulfone(SPSf)and concentration、the cooperation of inorganic material(o-CNT)blending ultrafiltration membrane(UF)as the support layer on the structure and performance of the aromatic polyamide thin film composite(TFC)reverse osmosis(RO)membrane were investigated systematically.The phase inversion method and interfacial polymerization(IP)were used for fabricating the blending supports and the RO membranes respectively.The influences of solvents and polymer concentration that varied between 16 wt% and 24 wt% used for preparation of casting solution were first explored on the properties of the PSf supports and the final RO membranes.Then,the doping content of SPSf in casting solution was adjusted to further regulate the structure and performance of the PSf/SPSf blending support with the purpose of matching the fabrication of the favorable polyamide TFC RO membrane.Finally,the effects of o-CNT concentration on the on the properties of the supports and the final RO membranes were further investigated.SEM、AFM imaging,surface pore natures(porosity,mean pore radius),contact angle and pure water flux analysis were applied for characterization of the PSf/SPSf blending supports.The experimental results are as follows: 1.Compared with DMAc and NMP,the selection of DMF and 20 wt% polysulfone is more conducive to the preparation of high permeability porous support layers and high performance polyamide reverse osmosis membranes.2.The supports prepared with hydrophilic polymer(SPSF)and relatively hydrophobic PSF possess higher porosity and better hydrophilicity.TFC RO membrane prepared by 6 wt% SPSF and 14 wt% PSF exhibited the most separation performance.3.The oxidized carbon nanotubes were introduced to regulate the structure and properties of the supports and the final RO membrane.The supports prepared with 0.5 wt% carbon nanotubes exhibited the highest porosity and maintained the same hydrophilicity.The polyamide layer prepared on it had the highest water flux and salt rejection.4.Factors influencing the polyamide structure include: 1)Pore structure of the supports.Porosity and pore size affect the structures of polyamide during the interfacial polymerization significantly.The high porosity of the support layer is beneficial to the formation of more polyamide structures.2)Hydrophobicity of the support layer.In general,compared with the hydrophobic PSF support layer,the more hydrophilic PSF/SPSF blend support is favor for uniform distribution of MPD,and tends to form a defect-free leaf-like polyamide structure and the polyamide exhibit the best separation performance.However,the nodular polyamide formed on the relatively hydrophobic PSF/o-CNT blend support layer has better permeability than the leaf-like polyamide formed on the hydrophilic PSF/SPSF,and the salt rejection rate is not reduced.The experimental results show that when the hydrophilicity of the support layer is within the range that can guarantee the integrity of the resulting polyamide structure,the more hydrophobic support layer is more conducive to the formation of a thicker,rougher,more permeable polyamide.3)The roughness of the base film.The higher roughness support tends to produce a rougher polyamide selection layer.