Insights into 1-butyl-3-methylimidazolium hydrogen sulfate recovery from wastewater by electrodialysis with heterogeneous ion-exchange membranes

Due to the negative impact of ionic liquids (ILs) on the environment and their high cost, it is very important to examine their recovery and recycling methods. Thus, in this study, research on 1-butyl-3-methylimidazolium hydrogen sulfate ([Bmim]HSO₄) recovery from wastewater by electrodialysis (ED) is presented. The influence of the initial [Bmim]HSO₄ concentration, the voltage, and the linear flow velocity on the effective [Bmim]HSO₄ recovery was examined. To assess the effectiveness of the proposed method, factors such as IL percentage recovery, degree of concentration, electric current efficiency, and energy consumption were determined. It was found that as the initial concentration of [Bmim]HSO₄ in the feed solution increased from 0.01 to 0.2 M, the [Bmim]HSO₄ recovery efficiency increased. A 2.3-fold concentration of the [Bmim]HSO₄ in the concentrate solution with a recovery of 98.8%, a current efficiency of 67.3%, and energy consumption of 28 kWh/m³ was achieved for ED of a 0.2 M [Bmim]HSO₄ solution using heterogeneous ion-exchange membranes. Additionally, the voltage and linear flow velocity affected the [Bmim]HSO₄ recovery. The highest ED efficiency for the recovery and concentration of [Bmim]HSO₄ was obtained at an applied potential of 4 V, a 2 cm/s linear flow velocity, and 0.2 M IL in the feed solution.