Ether-functionalized ionic liquids: Highly efficient extractants for hordenine

The application of ether-functionalized ionic liquids (ILs) as alternatives to conventional organic solvents in liquid-liquid extraction of hordenine was investigated. The parameters affecting the extraction ability of ILs such as the pH of the aqueous phase, the chemical structures of the IL cation and anion, the phase volume ratio and the hordenine concentration were evaluated. Experimental results indicate that the ether-functionalized ILs possess stronger extraction ability than the dialkylimidazolium-based ones. The extraction efficiency is highly dependent on the pH of the aqueous phase. Driving forces underlying the extraction processes include hydrogen-bonding interaction, hydrophobic interaction and steric hindrance effect. The recovery of hordenine from the IL phase and the recycling of the IL phase can be realized by using the pH swing effect. These results suggest that the ether-functionalized ILs are ideal alternatives to the conventional organic solvents for the extraction of hordenine from aqueous phases.