We have mixed cellulose acetate and Zeocarb-225 in different ratios, leading to the preparations of Membrane-1 and Membrane-2. Membrane potential, water content, and conductance measurements have been carried out to estimate and analyze the data in terms of equilibria and important electrochemical parameters. The Donnan equilibrium has been incorporated to estimate the activity coefficient of counterions, y(p)(M), and solute, y(+/-)(M) in the membrane phase along with the parameter, so called phi expressing non-ideality. Dependence of the extent of hydrophilicity of both membranes on mean electrolyte concentrations has been examined. Selectivity in membranes is discussed in terms of dissociation equilibria, K-d(s) and K-d(f). It has been found that membrane Surface charge density as increases with increasing ofexternal NaCl concentration. Dependence ofwater d transport number and cationic transport number on electrolyte concentration shows a similar trend of variation. At higher mean concentration of electrolyte, water transport number in Membrane-2 has a negative value. Membrane-2 has a higher value of water transport number than Membrane-1. The entropy production due to solute and water transport has been quantified for both the membranes in the light of nonequilibrium thermodynamics. The various type of interactions Such as solute-membrane, solute-water, and water-membrane are analyzed in terms of friction coefficients (f(ij)) of Spiegler's frictional pore model. In our case, an f(wm) < f(sm) < f(sw)-like trend is observed in both membranes. These frictional coefficients show close dependence on external electrolyte concentrations. Pore potential values of Membrane-1 and Membrane-2 have been worked out using the Poisson-Boltzrnann equation. In both systems pore potential values increase with increasing mean electrolyte concentrations. The transport through Membrane-1 and Mernbrane-2 tends to follow diffusion-control criteria, i.e., (D-+/- center dot C center dot d/(D +/- CM)-C-M center dot delta) >> 2. A slightly higher value of solute rejection is found in Membrane-2. (c) 2005 Elsevier Inc. All rights reserved.