Sorption, diffusion, and swelling characteristics of sodium alginate and its blend membranes with poly(vinyl alcohol) were investigated for water-acetic acid mixtures by using a gravimetric method at 30, 40, and 50degreesC. The membranes were characterized by X-ray diffraction and Fourier transform infrared techniques. Concentration-independent diffusion coefficients were obtained by applying Fick's relationship before completion of equilibrium sorption. Permeation coefficients were calculated from sorption and diffusion coefficients. Concentration profiles of liquids were computed considering the sheet geometry for the membrane by solving Fick's equation under suitable boundary conditions. Arrhenius activation parameters were computed for the transport processes. Experimental results and calculated quantities were discussed to understand membrane-solvent interactions. (C) 2004 Wiley Periodicals, Inc.