Performance tuning of chitosan-based membranes by protonated 2-Pyrrolidone-5-carboxylic acid-sulfolane DES for effective water/ethanol separation by pervaporation

Abstract

Today, the applicability of deep eutectic solvents (DES) in various fields, including membrane science and technology, is extensively investigated. In pioneering works, we have implemented different DES as a component of chitosan (CS)-based flat membranes for pervaporation (PV) separation. Herein, we present a new protonated (by sulphuric acid) 2-Pyrrolidone-5-carboxylic acid: sulfolane DES, as a green additive for its chemical blending and thus study its effect in CS structure. The resultant flat CS-based membranes have been characterized and tested for their ability in separating water molecules from ethanolic mixtures (10 wt% water in ethanol) using PV. Experiments revealed a progressive increase in total permeation along with increase of temperature in the range of 20–50 °C. Simultaneously, the value of separation factor was reduced. The maximum permeation (approximately 0.44 kg m−2 h−1) was observed for the highest experimental temperature, in which water was the main component, while the highest separation factor (approximately 518) was observed for lowest operating temperature. It was confirmed that application of selected DES allowed to improve the permeation rates in comparison with the bare CS membrane. As a perspective, such membranes could be tested for another hydrophilic pervaporation applications for the removal of polar compounds – with high applicability in biorefineries.