Effect of PEG additive on the morphology and performance of polysulfone ultrafiltration membranes

Flat sheet asymmetric polysulfone membranes were prepared by phase inversion method. Dimethyl acetamide was used as solvent and water was used as coagulant. Polyethylene glycol (PEG) of different molecular weights or different dosage of PEG 400 was used as the polymeric additives in the casting solution. The morphology of membranes was analyzed by scanning electron microscope and performance of membranes was evaluated in terms of pure water flux (PWF), protein rejection, porosity, contact angle, tensile strength, and elongation at break. Results show that PEG additive is a pore former and the addition of PEG additive can improve the hydrophilicity of membranes. PWF and porosity of membranes increase with increase in molecular weight of PEG or dosage of PEG 400. With increase in molecular weight of PEG from 400 to 20,000, the PWF increases from 340 L m(-2) h(-1) to 1390 L m(-2) h(-1). With increase in dosage of PEG 400 from 0% to 10%, the PWF increases from 0.81 L m(-2) h(-1) to 420 L m(-2) h(-1). The molecular weight cutoff (MWCO) of membrane keeps at 70,000 Da, and the pore size distribution of membrane skin layer becomes narrower. More PEG dosage weakens the mechanical properties of membrane; the tensile strength at break with PEG 1500 is maximum and the value is 5.62 MPa. (C) 2011 Elsevier B.V. All rights reserved.