A comparative study on the pervaporation separation has been attempted for water + 1,4-dioxane and water + tetrahydrofuran mixtures using sodium alginate and blend membranes of sodium alginate with 5, 10, and 20 mass % of poly(vinyl alcohol). Pure sodium alginate membrane has a selectivity of 111 to water at 0.35-mol fraction of water in the feed mixture containing 1,4-dioxane while for water + tetrahydrofuran mixture, the membrane selectivity to water was 291 at 0.31-mol fraction of water in the feed mixture. Pervaporation results have been discussed using the solution-diffusion principles. Arrhenius activation parameters for diffusion and permeation have been computed from the temperature-dependent pervaporation results. Furthermore, experimental results have been analyzed using the complete mixing and plug flow models to compute membrane area as well as design parameters that are useful in scale-up operations. The plug flow model is more appropriate than the complete mixing model to analyze the pervaporation results. (C) 2004 Wiley Periodicals, Inc.