Sorption, diffusion, and pervaporation characteristics of dimethylformamide/water mixtures using sodium alginate/polyvinyl pyrrolidone blend membranes

Separation of aqueous dimethylformamide (DMF) solutions in the concentration range of 0-100wt% were studied using sodium alginate (NaAlg)/polyvinyl pyrrolidone (PVP) blend membranes. The NaAlg was blended in different ratios with PVP. Prepared membranes were crosslinked with CaCl2 for testing in pervaporation (PV) separation of DMF/water mixtures. Effects of feed composition (0-100wt%), operating temperature (30-50 degrees C), and membrane thickness were investigated. Best results were obtained at the conditions of 75/25 NaAlg/PVP blend ratio (w/w), 40 degrees C temperature, 20 wt% DMF concentration, and 70 mu m membrane thickness. Blending of PVP with NaAlg increased permeation flux whereas it decreased the separation factor. NaAlg/PVP membranes gave separation factors of 5.5-27 for permeation flux of 0.96-1.81 kg/m(2) h depending on the operating temperature and the feed mixture composition. Arrhenius plot of permeation flux data versus reciprocal of temperature exhibited linear trends. Permeation activation energy of DMF and water in the PV was calculated as 6.76 and 1.88kcal/mol, respectively, using an Arrhenius type relationship. Sorption-diffusion properties of the NaAlg/PVP membranes were also investigated at the operating temperature and the feed composition. (c) 2007 Elsevier Ltd. All rights reserved.