A hydrophilic positively charged nanofiltration membrane was prepared by UV irradiation graft polymerization of diallydimethyl ammonium chloride (DADMAC) onto the surface of ultrafiltration membranes made of polyetherketone cardo (PEK-C). Analysis of ATR-FTIR and contact angles of the modified membrane showed that the grafting degree of the membrane and their hydrophilicity increased with the irradiation time and the monomer concentration in grafting solution. The modified nanofiltration showed a good retention to salts and the retention of the membrane to high valent cation and low valent cation was 95% and 65%, respectively. The separation performance of the membrane decreased in the presence of high valent negative counter-ions. The results show that the electrostatic effect played a major role in nanofiltration by charged membrane.

Key words: UV irradiation, polyetherketone-cardro, charged nanofiltration membrane, diallydimethyl ammonium chloride