Zeolite K-LTL-loaded sodium alginate mixed matrix membranes for pervaporation dehydration of aqueous-organic mixtures

In this work, zeolite K-LTL-loaded sodium alginate (NaAlg)-mixed matrix membranes were prepared by solution casting and cross-linked with glutaraldehyde. The pervaporation (PV) dehydration of isopropanol, 1,4-dioxane and tetrahydrofuran (THF) was tested at 30, 40, 50, 60 and 70 degrees C as a function of membrane thickness and feed compositions. Activation parameters for permeation were evaluated from the temperature-dependent pervaporation flux data. The results showed a simultaneous enhancement in flux and selectivity at azeotropic compositions of the mixtures due to the addition of K-LTL particles of different silica-alumina ratios in NaAlg matrix. Flux and selectivity values to water were higher for water-1,4-dioxane azeotrope than those of water-isopropanol and water-THF mixtures. Pervaporation results were discussed in terms of sorption-diffusion principles. Molecular sieving effect created due to uniform distribution of K-LTL zeolite particles and its hydrophilic nature in addition to its interaction with hydrophilic NaAlg is responsible to appreciably increase the membrane performance than pristine cross-linked NaAlg membrane. Thermodynamic treatment of sorption process was investigated typically for water+1,4-dioxane mixtures based on Flory-Huggins theory to explain the PV performance. Based on these results, permeance and driving force mechanisms were elucidated. The present membranes could withstand the repetitive cyclic PV runs on the laboratory level module. (C) 2007 Elsevier B.V. All rights reserved.