Preparation Of Polyethylenimine/polydopamine Composite Nanofiltration Membrane And Study On The Mass Transfer Mechanism Model

A new composite nanofiltration(NF)membrane with an active skin layer comprising only one polyelectrolyte bilayer were prepared through layer-by-layer deposition of oppositely charged polyelectrolytes of polyethylenimine(PEI)and polydopamine(PDA)on polyether sulfone(PES)ultrafiltration membrane.In this study,the influence of the concentration and deposition time of PEI,DA concentration and PDA self-assembling time on the separation performance and flux of composite NF membrane was studird.The charcateristics of the composite NF membrane was analyzed by electron microscopy(SEM),atomic force microscopy(AFM),water contact angle and zeta potential measurement.A DSPM-DE model for the interception of neutral PPCPs of composite NF membrane was established,and the prediction of the rejection of the composite nanofiltration membrane for 42 PPCPs was carried out using the model.The optimum preparation conditions of the composite NF membrane:the PEI concentration of polyelectrolyte bilayer was 2.0g/L and the soaking time was 30 min.The polyelectrolyte bilayer PDA solution was 3.0g/L,and the self-assembling time was 24h.The PEI concentration of the active layer was 3.0g/L and the soaking time was 30min.The SEM image showed that after polyelectrolyte deposition,the surface of the composite NF membrane becomed dense.The surface hydrophilicity of composite nanofiltration membrane was great.The Zeta potential of the composite nanofiltration membrane was-29.01 mV,it was negatively charged.The optimized membrane possessed a pure water permeability of 7.15L/m2 · h · Mpa and had a molecular weight cut-off about 500Da.The salt rejection for the composite NF membrane was MgSO4>MgCl2>K2SO4>Na2SO4>NaCl>KCl,it showed a high rejection to Mg2+and SO42-the rejection of MgSO4 is 98.0%.The rejection of the PPCPs is followed by Amlodipine(AML)>Atenolol(ATE)>Ibuprofen(IBU)>Carbamazepine(CBZ).DSPM-DE model can effectively predict the rejection of CBZ,Using the DSPM-DE models predicting the rejection of composite NF membrane to 42 kinds of PPCPs,the results show that the composite NF membrane rejections for most PPCPs can stay above 70.0%,it has a certain practical significance in water softening and the removal of trace concentrations of organic matter in the environment.