Effect of Poly(ethylene glycol) on Separations by Cellulose Acetate/poly(ether imide) Blend Membranes

Ultrafiltration membranes are largely being applied for macromolecular and heavy metal ion separations from aqueous streams. In this study, cellulose acetate (CA) and polyetherimide (PEI) based ultrafiltration blend membranes prepared in the absence and presence of poly(ethylene glycol) 600 (PEG 600) in various compositions were subjected to the separation of macromolecular proteins such as bovine serum albumin (BSA), egg albumin (EA), pepsin and trypsin. Toxic heavy metal ions such as Cu(II), Ni(II), Zn(II) and Cd(II) were subjected to separation by the blend membranes by complexing them with the polymeric ligand polyethyleneimine. The effects of polymer blend compositions and additive concentrations on the rejection and permeate flux of both proteins and metal ions are discussed. In general, it was found that CA/PEI blend membranes displayed higher permeate flux and lower rejection compared to pure cellulose acetate membranes at all additive concentrations. The extent of separation of proteins was found to be directly proportional to the molecular weight of the protein, while the extent of removal of metal ions depends on the affinity of metal ions to polyethyleneimine and the stability of the formed complexes.