Study on the recovery of ionic liquids from dilute effluent by electrodialysis method and the fouling of cation-exchange membrane

With the wide application of ionic liquids (ILs) in various fields, developing efficient techniques to recover ILs from effluent is an urgent demand for the cost reduction and the environmental protection. In this study, an electrodialysis (ED) method was used to recover 1-butyl-3-methylimidazolium chloride (Bmim]Cl) IL from aqueous solution as model effluent. The influences of initial IL concentration and applied voltage on the current efficiency, removal ratio, desalination ratio, membrane flux and specific energy consumption during the ED process were investigated. It was found that the removal ratio and desalination ratio increases with the increasing of initial IL concentration and applied voltage. The current efficiency decreases with the increasing of initial IL concentration and the current efficiency reached the maximum value of 94.3% at 25 V. Besides, as the applied voltage increases, the membrane flux increases and the specific energy consumption decreases. Moreover, the fouling of cation-exchange membrane was also discovered after the desalination of IL. The deposits on the surface or into the membrane which is probably caused by Bmim]⁺ was characterized by scanning electron microscopy, elemental analysis and Fourier transform infrared.