Preparetion And Properties Of Polyamide Based Hybrid Nanofiltration Membranes

At present,low permeation flux and membrane fouling are the key issue for application and development of nanofiltration membranes.Therefore,preparing nanofiltration membranes with high permeation and antifouling property is the necessary method to improve membrane performance.High permeation flux and antifouling membranes preparation is the aim of this work,reasonable choice of membrane materials can endow specific performance of the prepared membranes and optimization of process conditions so as to achieve in the optimum performance of each prepared membrane.The main research content is as follows:Firstly,g-C₃N₄ nanosheets?CNs?was incorporated into PA selective layer to improve membrane surface properties by interfacial polymerization.g-C₃N₄ is a kind of hydrophilic and porous analogous graphene material with two dimensional sheet structure.The incorporation of g-C₃N₄ into membrane surface could improve permeation flux and antifouling property.Besides,there are free amino in the structure of g-C₃N₄,which can participate in the reaction of interfacial polymerization,resulting in stronger stability and improvement of compatibility between g-C₃N₄ and PA.Under the condition of filtration pressure of 0.2 MPa,compared with pure PA nanofiltration membrane,the water flux of CNs modified polyamide?PA/CNs?nanofiltration membrane increased from 20.9 L m^-2 h^-1to 37.6 L m^-2 h^-1,while the rejection of sodium sulfate solution remain 84%.Secondly,zwitterionic titanium nanotube?Z-TNT?was incorporated into polyamide?PA?separation layer to improve membrane properties by interfacial polymerization.Z-TNT is a kind of high hydrophilic material,the introduction of Z-TNT can improve hydrophilicity of membrane surface,promoting the permeation flux and antifouling performance of membranes.Meanwhile,the surface of Z-TNT has a layer of decorated zwitterion,zwitterion can adjust surface charge and improve the membrane antifouling performance.At the condition of filtration pressure of 0.2 MPa,compared with PA membrane,the water flux of Z-TNT modified polyamide?PA/Z-TNT?nanofiltration membrane increased from 20.9 L m^-2 h^-1 to 44.94 L m^-2 h^-1,while the rejection of sodium sulfate solution kept 88.9%.Finally,the porous?-CD-containing polymers?P-CDPs?were doped into PA selective layer by interfacial polymerization to improve membrane property.P-CDPs is a kind of porous material with high surface area and stable channel.The special structure of P-CDPs provides stable and fast water channel,resulting in the water molecules easy to pass.In addition,the material inherits the advantages of?-CD,has good hydrophilicity and biocompatibility.Therefore,P-CDPs is a kind of good additive choice for preparation of PA nanofiltration membranes.At the condition of filtration pressure of 0.2 MPa,compared with PA membrane,the water flux of P-CDPs modified polyamide?PA/P-CDPs?nanofiltration membrane increased from 33.4 L m^-2 h^-1 to 42.0 L m^-2 h^-1,while the rejection of Na₂SO₄?MgSO₄ and NaCl is 97.0%?88.1%and 19.2%respectively.