The influence of polymer concentration on performance and morphology of asymmetric ultrafiltration membrane for lysozyme separation

In this study, the effects of polymer concentrations on the morphology and performance of ternary mixtures of polyethersulfone/N-methypyrolidone/water membrane dope solution were investigated. Three dopes with different polymer concentrations (13% [UF13], 15% [UF15] and 17% [UF17] polyethersulfone) were prepared via simple dry/wet phase-inversion technique. The membranes were characterised in terms of permeability coefficient, membrane morphology, Molecular Weight Cut-off (MWCO) and membrane surface. Separation performance of lysozyme show that the optimum transmissions at pressure of 3 bars for UF13, UF15 andUF17 membranes were 95.1, 97.4 and 46.2%, respectively and optimum flux were 105×l0-6, 10.4×10-6 and 1.6×l0-6 mVm2 sec, respectively. As polymer concentration increased, the morphology of membranes also changed from a large finger-like structure to a thin finger-like structure with the presence of sponge-type and macrovoids. UF15 membrane was selected as the optimum membrane since it was able to promote the highest lysozyme transmission together with appropriate flux. Its characteristics as a negatively-charged membrane, with zeta potential of -62 mV and MWCO around 43 kD was provided great evidence for its suitability in the lysozyme separation process. This study demonstrated that the polymer concentration highly influenced the performance and morphology of UF membranes which in turn exhibited an improvement in separation ability. © 2010 Asian Network for Scientific Information.