Sorption of sodium benzenesulfonate by charged cellulosic membranes.

Abstract

Equilibrium sorption of sodium benzenesulfonate (NaSO3Ph) by charged cellulosic membranes was determined by measuring both of the cation and anion concentrations at 25°C. The membranes used were carboxyethyl cellulose (CEC), sulphoethyl cellulose (SEC), and phosphorylated cellulose (PC).The results were analyzed by the simple Donnan model in which a homogeneous charge distribution is assumed. In the range of C (aqueous salt concentration) >Cx (effective fixed charge density), the Donnan approach reproduced the experimental results quite well. In the range of C<Cx, however, the deviation was clearly observed, especially for SEC and PC membranes which have high Cx.The results were further interpreted by Petropoulos's theory, which is based on the nonhomogeneous charge distribution. By this method the sorption data could be explained well over all range of salt concentrations (1×10-3_??_4×10-1 mol/l). The Z-factors as the measure of the non-homogeneous charge distribution were estimated as 0.72_??_0.81 for NaCl and 0.82_??_0.85 for NaSO3Ph.The partition coefficients of NaSO3Ph were lower than NaCl. The effects of ionic size on these values were suggested.