Interfacial State Change of Cellulose Triacetate Membrane by Adsorption of Polyelectrolyte

Lysozyme, albumin, and PAS-H (poly diallyl dimethyl ammonium chloride), which are positively and negatively charged proteins, and cationic polysulfones, respectively, were adsorbed by a cellulose triacetate (CTA) membrane to investigate their effects on ionic transport through the membrane. The interface states between the membrane and the adsorption layer are discussed based on the measurements of contact angle and membrane potential and atomic force microscopy (AFM). The contact angle shows that the membrane changed from hydrophobic to hydrophilic due to adsorption of the above substances. AFM imaged the aggregates on the surface and showed that lysozyme, in particular, penetrates the membrane pores, making them shallower and decreasing their porosity. The results of membrane potential measurements showed that lysozyme and albumin did not change the membrane charge state, but PAS-H changed it from negative to positive. The permeability coefficients of KCl and K2HPO4 varied significantly with the adsorption of each polyelectrolyte. In particular, the permeability coefficient of phosphate through the lysozyme-adsorbed membrane increased to twice that of the nonadsorbed membrane. Such polyelectrolyte adsorption on the membrane surface can be used for the modification of commercial artificial kidney phosphate extraction.