Physical adsorption of water-soluble polymers on hydrophobic polymeric membrane surfaces via salting-out effect

Abstract

In this study, polyvinylamine (PVAm), poly(vinyl sulfonic acid) (PVSA), and poly(styrene sulfonic acid) (PSSA) were physically adsorbed, using the ‘salting-out’ effect, onto hydrophobic membrane surfaces such as polysulfone (PSf), polyvinylidene fluoride (PVDF), and polyethylene (PE), commonly used as ultrafiltration (UF) and microfiltration (MF) membranes. The physical adsorption of such hydrophilic polymers were monitored as a function of concentration, time, type of salt, and ionic strength, and the resulting adsorbed membranes were characterized using a contact angle measurement, a gravimetric analysis, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). In most cases, with increasing the adsorption time, the wettability of surface-modified membranes was significantly improved. Physical adsorption of hydrophilic polymers on hydrophobic membrane surfaces, facilitated by the salt-out effect, was almost achieved within a few minutes. Typically, a contact angle of 47° was observed at ionic strength (IS)=0.1Mg(NO3)2·6H2O and PVAm 2,000 ppm for a PSf membrane. The weight changes by adsorption were varied with adsorption time in the cases of PVSA and PSSA, while the weight change for PVAm approached the equilibrium rapidly after the initial adsorption time. Open image in new window