Preparation of internally pressurized polyamide thin-film composite hollow fiber nanofiltration membrane with high ions selectivity by a facile coating method

Abstract

Internally pressurized polyamide thin-film composite (TFC) hollow fiber nanofiltration (NF) membrane with high ions selectivity was prepared by a facile coating method including the dip-coating of the aqueous phase and reverse direction coating of organic phase. Surface composition and morphologies of the prepared NF membrane were characterized by ATR-FTIR, FESEM and AFM. Membrane hydrophilicity was evaluated by Water Contact Angle (WCA) measurements. The dip-coating time of the aqueous phase and reverse direction coating time of organic phase were optimized. The results indicated that the ultra-thin functional layer was successfully formed on the lumen side of hollow fiber PSF substrate membrane. Under the optimized conditions including the dip-coating time of 20 min and reverse direction coating time of 60 s, the prepared TFC hollow fiber NF membrane exhibited an excellent separation performance with the 99.5 % rejection of MgSO4 (1 g/L) and pure water flux of 43.3 L/m2h at 0.7 MPa. The prepared NF membrane showed a high selectivity with the separation factor of MgSO4/NaCl) of 7.8. NF membrane exhibited a uniform separation performance along fiber length compared with the traditional single direction coating.