Hydrophilic nanofiltration membranes with good retention to bivalent salts were prepared by graft polymerization of acrylic acid (AA) onto surface of cardo polyetherketone (PEK-C) ultrafiltration membranes. The influence of isopropanol (i-PrOH) as transfer agent on the graft polymerization and the performance of nanofiltration membranes were studied. The results of FTIR-ATR, contact angle, SEM and AFM showed that the presence of i-PrOH did not disturb the graft polymerization of AA. It was in favor of membrane permeation increase. Although the retention to salts was a little decreased, it could be improved by increasing the irradiation time or irradiation intensity. It was found that when the weight ratio of i-PrOH over AA was higher than 0.75, the flux of modified membrane was linearly increased with i-PrOH concentration while the retention to salt was kept unchanged. It was suggested that the transfer reaction of i-PrOH should increase grafting density and surface charge, which would be in favor of salt retention.

Key words: photo-induced polymerization, ultrafiltration membrane, nanofiltration membrane, cardo polyetherketone, acrylic acid, isopropanol