ABSTRACT
Ionic liquids (ILs), named also as liquid salts, are compounds that have unique properties and molecular architecture. ILs are used in various industries; however, due to their toxicity, the ILs' recovery from the postreaction solutions is also a very important issue. In this paper, the possibility of 1,3-dialkylimidazolium IL, especially the N,N-dibutylimidazolium chloride ([C4C4IM]Cl) recovery by using the electrodialysis (ED) method was investigated. The influence of [C4C4IM]Cl concentration in diluate solution on the ED efficiency was determined. Moreover, the influence of IL on the ion-exchange membranes' morphology was examined. The recovery of [C4C4IM]Cl, the [C4C4IM]Cl flux across membranes, the [C4C4IM]Cl concentration degree, the energy consumption, and the current efficiency were determined. The results showed that the ED allows for the [C4C4IM]Cl recovery and concentration from dilute solutions. It was found that the [C4C4IM]Cl content in the concentrates after ED was above three times higher than in the initial diluate solutions. It was noted that the ED of solutions containing 5-20 g/L [C4C4IM]Cl allows for ILs recovery in the range of 73.77-92.45% with current efficiency from 68.66% to 92.99%. The [C4C4IM]Cl recovery depended upon the initial [C4C4IM]Cl concentration in the working solution. The highest [C4C4IM]Cl recovery (92.45%) and ED efficiency (92.99%) were obtained when the [C4C4IM]Cl content in the diluate solution was equal 20 g/L. Presented results proved that ED can be an interesting and effective method for the [C4C4IM]Cl recovery from the dilute aqueous solutions.
Subject(s)
Ionic Liquids , Chlorides , Halogens , Salts , WaterABSTRACT
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.
