Nanofiltration membrane prepared from cardo polyetherketone ultrafiltration membrane by UV-induced grafting method

Hydrophilic nanofiltration membranes were prepared by graft polymerization of hydrophilic monomers onto the surface of ultrafiltration membranes made from cardo polyetherketone (PEK-C). The method consists of a UV irradiation in the presence of acrylic for an in situ graft polymerization of polyacrylic acid (PAA) on the surface of the UF membranes. The effect of UV intensity, irradiation time and monomer nature on the membrane performances were investigated. Analyses by Fourier transform infrared in attenuated total reflection mode, contact angles and atomic force microscopy of the modified membrane surface showed that the degree of grafting of the membrane surface and their hydrophilicity increased with the irradiation time. The retention of sodium chloride and sodium sulfate of the membrane with poly(acrylic acid) grafted for I min of UV irradiation under a 8.7 mW/cm(2) lamp were 57 and 95.7%, respectively, while the water flux of the membrane was ca. 25 L m(-2) h(-1), at 0.8 MPa. The changes in the membrane permeability and the salt retention with different grafting parameters suggest that, under a high enough irradiation power and monomer concentration in the surrounding medium, enough PAA chains are grafted on the pores wall to convert the pores of an UF membranes to the NF-type pores (sodium sulfate retention close to 100%) within a few minutes. Further irradiation adds new PAA grafts in the plain polymer surface, without significant changes in the pores, i.e. in the membrane performances. The grade of the obtained NF membrane can be controlled by monitoring the monomer concentration or the irradiation power in order to graft progressively PAA chains on the pores. (c) 2005 Elsevier B.V. All rights reserved.