Plasma surface modification of polypropylene microfiltration membranes and fouling by BSA dispersion

Fouling is the major obstacle in membrane processes applied in protein filtration. To overcome the problem, the polypropylene microfiltration membranes (PPMMs) were surface-modified by low temperature NH3 plasma treatment. Structural and morphological changes on the membrane surface were characterized by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The change of surface wettability was monitored by contact angle measurements. The pore size and distribution were evaluated by mercury porosimetry. The static water contact angle of the modified membrane reduced obviously. The relative pure water flux of the modified membranes had a maximal value for the plasma treatment time of 1 min. To assess the relation between the plasma treatment and the membrane fouling by bovine serum albumin (BSA), the filtration and the adsorption of BSA experiments were carried out. It was found that the surface modified membranes showed better regeneration performances, i.e. higher flux recoveries after water and caustic cleaning than those of the nascent PPMM. Flux recoveries after water and caustic cleaning for the NH3 plasma treated PPMM for 1 min were 51.1 and 60.7%, respectively higher than those of the virgin membrane. The results demonstrated that the bovine serum albumin adsorption was suppressed significantly by plasma surface modification.