Charged Nanofiltration Membrane Modification And Desalination Performance Research

Layer-by-layer(LBL) self-assembly technology was more and more popular in the modification of membrane because of its advantage. Its thickness of the ultra-thin layer and charge density could be controlled and preparation method was simple.Poly (styrene-sulfonate)(PSS) was selected as the anionic polyelectrolyte, and poly (diallyl-dimethyl ammonium-chloride)(PDADMAC) was chosen as the cationic polyelectrolyte. Polysulfone ultrafiltration membrane was modified by LBL. We studied some affecting factors of the modified membrane for desalination, such as layer pair number, the outermost layer of polyelectrolyte, assembly time, concentration of polyelectrolyte, and so on. We also studied the stability of the modified membrane. Separation performances of the modified membranes were studied with1g·L-1MgSO4. Results demonstrated that MgSO4rejection increased from20%(unmodified) to92%(modified).Nanofiltration membrane was modified by layer-by-layer self-assembly technology. Poly (styrene-sulfonate)(PSS) was selected as the anionic polyelectrolyte, and poly (diallyl-dimethyl ammonium- chloride)(PDADMAC) was chosen as the cationic polyelectrolyte. The modified nanofiltration membranes were characterized by Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). The dynamics of modified membrane was first studied by AFM. The LBL modification of nanofiltration membranes were first used to remove the salts of glutathione solutions. We studied some affecting factors of the modified membrane for removing the salts of glutathione solutions, such as layer pair number, the outermost layer of polyelectrolyte, assembly time, concentration of polyelectrolyte, and so on. We also studied the stability of the modified nanofiltration membrane. Separation performances of the modified nanofiltration membranes were studied with1g·L-1synthetic glutathione solutions, containing2g·L-1NaCl. Results demonstrated that the glutathione rejection increased from74%(unmodified) to97%(modified), whilst the selectivity for NaCl over glutathione increased from2.8(unmodified) to23(modified).