Study on the Effectiveness of Simultaneous Recovery and Concentration of 1-Ethyl-3-methylimidazolium Chloride Ionic Liquid by Electrodialysis with Heterogeneous Ion-Exchange Membranes.

Dorota Babilas,Piotr Dydo,Anna Kowalik-Klimczak

doi:10.3390/ijms222313014

Abstract

Due to the extensive range of ionic liquids (ILs) used in industry, an efficient recovery method is needed. In this study, the effectiveness of a simultaneous concentration and recovery method was investigated for 1-ethyl-3-methylimidazolium chloride ([Emim]Cl), an IL that was recovered using electrodialysis (ED). The optimal operational parameters for electrodialytic recovery were determined empirically. The variables that were investigated included the concentration of IL, applied voltage, linear flow velocity and the diluate-to-concentrate volume ratio. The recovery of [Emim]Cl, the concentration degree, the [Emim]Cl flux across membranes, the current efficiency, as well as the energy consumption were determined. The results of the experiments confirmed that [Emim]Cl concentration and recovery can be achieved using ED. The highest ED efficiency was obtained when a 2 V electric potential per one membrane pair was applied, using a 2 cm/s linear flow velocity, and by adjusting to 0.2 M IL in the feed solution. By using ED, a 2.35-fold concentration of [Emim]Cl with a recovery of 90.4% could be achieved when the diluate-to-concentrate volume ratio was 2. On the other hand, a 3.35-fold concentration of [Emim]Cl with a recovery of 81.7% could be obtained when the diluate-to-concentrate volume ratio was increased to 5.

Highlights

IntroductionThe melting points of ionic liquids (ILs) are generally below room temperature, occasionally below 0 ◦ C, and they are classified as molten salts [1,2]
An ionic liquid (IL) is a liquid salt
The Limiting Current Density (LCD) depended upon the [Emim]Cl concentration in the diluate solution

Summary

Introduction

The melting points of ILs are generally below room temperature, occasionally below 0 ◦ C, and they are classified as molten salts [1,2]. ILs are characterized, for example, by high thermal and chemical stability, negligible vapor pressure, non-flammability and a wide electrochemical window. It should be noted that ILs may be toxic [3,4]. Due to their unique chemical and physical properties, they can be used in fields such as in wastewater treatment, electrochemistry, catalysis, analysis and biomass valorization [5]. ILs are classified on the basis of their properties and their applications, such as task-specific ILs, supported ILs, chiral ILs, protic ILs, bio ILs, polarizable ILs, metal salt ILs, switchable-polarity solvents and deep eutectic solvents [6,7]

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Conclusion