Preparation And Separation Performance Of Aromatic Polyamide Nanofiltration Membrane

As a synthesize macromolecule material, aromatic polyamide has better thermic and chemic stability than cellulose acetate and other kinds of materials for membrane preparing ,owning to its special molecular structure .It is practical and meaningful to develop the aromatic polyamide nanofiltration(NF) membranes. This can not only exactly fills the gap between ultrafiltration(UF) and reverse osmosis, but also provides a new kind of membrane.The aromatic polyamide used in this study is polyisophthaloyl metaphenylene diamine.In this work, flat nanofiltration(NF) membrane with small molecular weight cut-off (MWCO)was successfully prepared by means of Phaseinversion method, with aromatic polyamide as raw material and dimethylacetamide(DMAc)as solvent. The effects of aromatic polyamide concentration in the casting solution, the concentration of the additive in the casting solution ,the evaporation time of nascent membrane, the temperature and composition of coagulation bath and the thickness of membranes on the performance of nanofiltration (NF )membranes were investigated .Aromatic polyamide hollow fiber nanofiltration membrane was studied by means of dry-wet spinning on the bases of flat nanofiltration(NF) membrane. The properties of membrane and the parameters of spinning technology are affected by the fluidity of spinning solution , spinneret's temperature, vaporing distance pressure of internal liquid and latter treatment. Based on the discussing of above ingredients ,a optimal spinning technology was found .Microstructure prepared membrane was analysed by Scanning Electron Microscopy(SEM).The separation performance of prepared membrane and some operating factors were mainly discussed.The results show that ,at 25℃,0.5MPa ,the rejection ratio of 500mg /L MgSO₄ solution is 27.43%, the rejection ratio of 500mg/L Na₂SO₄ solution is 30.10%.The membrane prepared showed a good PEG-1000 rejection rate up to 67.28 % .The nanofiltration membrane has better resistance to organic solutes and contamination.