Preparation Of Amino-polyethersulfone/Polyamide Composite Nanofiltration Membrane

In practical applications,there is a balance problem between low flux and selective separation performance of the nanofiltration membrane,and low interface adhesion between PA layer and base membrane for the nanofiltration membrane prepared through traditional interface polymerization reaction,which greatly limits the service life of the nanofiltration membrane and affects its practical application.In order to solve the above problems,in this project,double（4-fluorophenyl）sulfone（FPS）,double（3-amino-4-hydroxy-phenyl）sulfone（BAPS）and 4,4-dihydroxy diphenyl phenol polymerization reaction,the introduction of hydrophilic-NH₂ functional group into the polyether sulfone skeleton,synthesis of a hydrophilic amino-carrying polyether sulfone（PES-NH₂）.Further,a series of base membranes were obtained by blending the synthesized PES-NH₂with PES in different proportions.And further explore by infiltration experiments on the substrate membrane with piperazine（PIP）and trimesoyl chloride（TMC）as the two phase monomers on interfacial polymerization reaction optimum reaction conditions of preparation of polyamide composite nanofiltration membrane:PIP concentration 0.6 wt%,TMC concentration 0.3 wt%,the reaction time is 10 min,heat treatment temperature of 70℃,90 s,heat treatment time and get the corresponding series under the condition of the composite nanofiltration membrane PES NF,PES/PES-NH₂-10 NF,PES/PES-NH₂-30 NF,PES/PES-NH₂-50 NF.Finally,the properties of the prepared series of PES/PES-NH₂ composite nanofiltration membranes were compared with traditional PES composite nanofiltration membranes.The chemical composition,morphology,hydrophilicity and charge of the membrane surface were characterized by Fourier transform attenuated total reflection infrared spectroscopy（ATR-FTIR）,X-ray photoelectron spectroscopy（XPS）,field emission scanning electron microscopy（FE-SEM）,atomic force microscopy（AFM）,and static water contact Angle evaluation（WCA）.The permeation flux of the prepared polyamide composite nanofiltration membrane,the retention of inorganic salt solution,the circulation pollution of bovine serum albumin（BSA）,and the stability of continuous separation for 15 days were tested by cross-flow permeation device to demonstrate the relevant performance of nanofiltration membrane permeation and separation.The experimental results show that compared with the PES composite membrane,the water flux for the PES/PES-NH₂ NF membrane at operating pressure of 0.6 MPa increased from 25.3±3.1 L·m^-2·h^-1 to 59.5±2.2 L·m^-2·h^-1.Overall all membrane’s ability to reject kinds of inorganic salt as Na₂SO₄>Mg SO₄>Mg Cl₂>Na Cl,showing typical burden electric nanofiltration membrane separation performance,modified membrane withholding rate of different inorganic salts are improved,PES/PES-NH₂ NF of Na₂SO₄ intercept rate reached 96%,up by more than6%,and the rejection rate of Mg SO₄ reached more than 94%,increased by about 12%,the modified composite nanofiltration membrane has a more dense membrane pore structure,the stronger the membrane surface electronegativity,showed close burden electric nanofiltration membrane separation properties.In the 15-day long running test,the rejection of Na₂SO₄ by modified nanofiltration membrane was still more than 86%,which showed higher separation stability and higher antifouling performance compared with PES NF’s retention rate of 69.3%.According to the analysis of experimental result,due to the rich in the amino modified membrane material,membrane in amino can participate in piperazine（PIP）and the interface between the three benzene formyl chloride（TMC）polymerization,the PA layer and PES/PES-NH₂ covalent bond formed between the membrane stability,and hydrophilic modification of membrane material will influence the diffusion reaction of aqueous monomer PIP,thus leading to the crosslinking degree of PA layer,combined with the basement membrane changes,both with high flux,high intercept amino polyether sulfone,high separation on the stability of PES/PES-NH₂ composite nanofiltration.