The influence of polarization of the sorbent on sorption of albumin by carbon fibers

Abstract

The sorption of bovine serum albumin (BSA) on non-charged and polarized surfaces of carbon fibers (ACF) and carbon fibet~ modified with titanium hydroxide (ACF-Ti) was studied. It was shown that cathodic polarization considerably influences the reversibility of the BSA sorption and decreases the BSA sorption by ACF and ACF-Ti to a larger extent than anodic polarization. A change in the surface charge mainly influences sorption of albumin by ACF-Ti, which is due to different surface properties of the initial and titaniumcontaining adsorbents.Key words: adsorption, electrosorption, polarization, surface charge, carbon fibers, protein, titanium hydroxide, modified sorbents.Electrochemical polarization of carbon sorbents, possessing highly extensive surface areas, good electrical conductivities, and relatively high adsorption capacities, t provides the possibility of affecting the equilibria in adsorbent--adsorbate systems in a specified way. Modification of the surface of carbon materials by, for instance, titanium hydroxide, which forms strong coatings and is stable over a broad pH range, makes it possible to change the electrochemical properties of polarizable adsorbents over wide limits. Electrochemical polarization of a sorbent at an appropriately chosen potential can be used to control the adsorption properties, to desorb various organic compounds, and to restore the adsorption capacity of the adsorbent, t However, sorption of proteins on an electrochemically polarized carbon surface, in particular, on the surface of activated fibers, has scarcely been studied, although the use of surface polarization (electrosorption) for protein--surface systems could substantially extend the potential of methods for protein separation based on sorption phenomena.Adsorption in the system comprising a model protein (bovine serum albumin (BSA)) and activated fibers has been studied previously)The purpose of the present work is to study the influence of electrochemical polarization on the sorption properties of this system. ExperimentalActivated carbon fibers (ACF) Actylen of the braid type were used as sorbents. In addition to the initial ACF, fibers coated 3 with titanium hydroxide (ACF-Ti) were used.The specific surface area of the adsorbents found by the BI-T method using adsorption of nitrogen, the micropore volume, and the effective pore radius for the adsorbents studied were 1000 m 2 g-l, 0.4 cm a g-I; and 4 A, respectively_ The BSA preparation was produced at the NIIEV research institute (Minsk). The content of BSA in solutions was determined by the Lowry method. 4 Adsorption of BSA was studied under static conditions in a standard three-electrode cell. All measurements were carried out in the universal sodium phosphate-acetate-borate buffer solution. The reversibility of the adsorption on a noncharged surface was studied using BSA labeled with the 125I isotope. For this purpose, the sorbent containing 1251-BSA, preadsorbed under the conditions studied, was placed in a solution of native BSA and the decrease in the "f-ac...