Separation characteristics of hydrophilic ionic liquids from ionic liquids-water solution by ultrasonic atomization

Ionic liquids (ILs) have attracted much attention as promising alternatives for volatile organic solvents. Although the applications of ILs have been found in a diverse range of fields, there are a limited number of methods for the recovery of ILs so far. As an efficient separation method, therefore, ultrasonic atomization has been attempted to recover hydrophilic ILs, [Bmim][BF₄], from ILs-water solution. In order to examine the separation characteristics of hydrophilic ILs-water solution, ultrasonic atomization of hydrophilic ILs-water solution was performed under various operating conditions such as initial ILs concentration, ultrasonic electric power, carrier gas flow rate, and operating temperature. The result showed that hydrophilic ILs recovery yield increased with a decrease in ultrasonic electric power, gas velocity, and temperature. As an increase in initial ILs concentration, however, higher ILs recovery yield was obtained. After 6 h of ultrasonic atomization of 50% (v/v) [Bmim][BF₄]-water solution, 93.4% of initial ILs amount was recovered without any changes in their structure at ultrasonic power of 10 W, carrier gas flow of 5 L/min and temperature of 20 °C. It demonstrated that ultrasonic atomization could be used for the recovery of ILs from ILs-aqueous solution.