Pervaporative separation of ethylene glycol/water mixtures by using cross-linked chitosan membranes

Chitosan (CS) is one of the most widely used pervaporation membranes in the world today. A novel method for cross-linking CS membranes using phosphoric acid in alcohol baths was investigated in this study for the separation of ethylene glycol (EG)/water mixtures. The cross-linked membranes were subjected to sorption studies to evaluate the extent of interaction and degree of swelling in pure as well as binary mixtures of the two liquids. In order to gain a more detailed picture of the molecular transport phenomenon, we have performed sorption gravimetric experiments at 30 degrees C to compute diffusion, swelling, sorption, and permeability coefficients of phosphorylated chitosan (P-CS) membranes in the presence of ethylene glycol and water. The effects of experimental parameters such as feed composition, membrane thickness, and permeate pressure on separation performance were determined. The membranes were characterized before and after cross-linking by Fourier transform infrared (FTIR) analysis and thermogravimetric analysis (TGA) to verify cross-linking and to observe the thermal degradation range of the polymer. The membrane appears to have a good potential for breaking the boiling mixture of ethylene glycol/water since a moderately good selectivity of 234 was obtained at a reasonable flux of 0.37 kg/m(2)center dot h. The separation factor was found to improve with decreasing feedwater concentration whereas flux decreased correspondingly. Increasing the membrane thickness decreased the flux but had a less profound effect on the separation factor. Higher permeate pressure caused a reduction in flux and an increase in selectivity.