Robust and high selective chitosan asymmetric Membranes: Relation between microporous structure and pervaporative efficiency in ethanol dehydration

Abstract

• Asymmetric membranes are prepared in the presence of ethanol in chitosan solution. • Fabricated membrane is used for ethanol dehydration via pervaporation. • Changes of membrane structure during pervaporation process are extensively analyzed. • Analysis of transport parameters for transient and quasi-stationary state is provided. To improve the process of ethanol dehydration, asymmetric chitosan membranes were prepared and applied in the pervaporation process. A porous structure was obtained by adding absolute ethanol into chitosan solution. Fabricated membranes were comprehensively characterized by means of contact angle measurements, degree of swelling analysis, scanning electron microscopy, positron annihilation lifetime spectroscopy and wide angle X-rays scattering, to provide an extensive analysis of their physicochemical properties. The results showed a strong correlation between structure, amount and size of pores, and separation effectiveness of investigated membranes. Additionally, an interesting phenomenon of changing in membrane structure during pervaporation process was observed and was found to cause a nonlinear time dependence of transport and separation parameters. Consequently, the best performance of PV separation of 96 vol% ethanol (feed) was obtained for a membrane prepared from casting solution containing 0.1 ml of absolute ethanol, for which the values of separation factor and permeate flux reached 599.7 and 3.534 kg∙m −2 ∙h −1 , respectively.