UV-assisted graft polymerization of N-vinyl-2-pyrrolidinone onto poly(ether sulfone) ultrafiltration membranes using selective UV wavelengths

Low protein fouling 50 kDa poly(ether sulfone) ultrafiltration membranes were produced by UV-assisted graft polymerization of the monomer 1-vinyl-2-pyrrolidinone by using a dip modification technique without loss of protein rejection. UV lamps with an emission wavelength maximum of 300 nm and two specially selected UV light filters, benzene and an aromatic polyester film, were used to filter out 254 nm wavelength light which was found to be responsible for severe loss of protein rejection. The modified membranes that performed the best were prepared by using 300 nm lamps and the benzene filter. With increasing degree of grafting, these membranes exhibited up to 20% higher surface wettability (cos Theta) = 0.830.89) than the base membrane (cos Theta = 0.74), which translated into lower irreversible flux loss (-0.05 to 0.03 compared with 0.42). While the protein rejection remained unchanged after modification, the permeability of the membranes decreased from 6.5 to 0.3 1 m(-2) h(-1) (kPa)(-1) with increasing degree of grafting as a result of pore plugging by the grafted chains. These membranes exhibited similar irreversible flux loss (0.03 vs similar to0), similar permeability (1.2 vs 1.8 1 m(-2) h-1 (kPa)(-1)), and higher rejection (97.4 vs 93.4%) as compared with a 50 kDa regenerated cellulose membrane.