Novel hybrid composite membranes have been prepared by incorporating 5 and 10 wt.% of sodium montmorillonite (Na+MMT) clay particles into sodium alginate (NaAlg) and crosslinked with glutaraldehyde. Pervaporation (PV) separation performance of the hybrid composite membranes has been investigated for dehydration of isopropanol, 1,4-dioxane and tetrahydrofuran (THF) from their aqueous solutions at 30 degrees C. The effect of Na+MMT in sodium alginate membrane has been investigated in the pervaporation dehydration. It is found that Na+MMT particles can be intercalated in the aqueous polymer solution. The driving force for Na+MMT adsorption is entropic, which involves at least partial replacement of water of hydration associated with exchangeable cations in the clay galleries. The results of PV experiments demonstrated that addition of Na+MMT clay particles would help to increase the selectivity to water over that of pristine NaAlg membrane by pushing its limit to infinity giving a moderate flux. Permeation fluxes of the hybrid composite membranes were lower than those observed for plain NaAlg membrane. (C) 2006 Elsevier B.V. All rights reserved.