Ultrasonication-assisted chelating ligand-free extraction of Pb(II) from aqueous solution by using room temperature ionic liquids

This work aims to study the extraction of Pb(II) from contaminated aqueous solutions using imidazolium-based room temperature ionic liquids as sole extracting agent, i.e., without using any chelating agent and mixing agent. Secondly, ultrasonication technique is employed first time, to facilitate the swift contact of potentially toxic metal ions present in aqueous solution with ionic liquid. Furthermore, various salting-out agents were investigated to reduce the leaching of ionic liquid (IL) cations into aqueous phase upon extraction of toxic metal ion. > 90% of Pb(II) was removed from artificially contaminated aqueous solution using 100 mg of IL in 6 min sonication time. Moreover, the used ionic liquid was proved to be selective for Pb(II) in real water conditions. MgSO4 salt at 1.0 M concentration found to be superior salting-out agent without having any adverse effect on the extraction efficiency. Determination of total dissolved organic carbon in treated aqueous solution was used as potential tool to propose the mechanism of metal ions transfer to ionic liquid phase from aqueous solution. This study show that ultrasonication-assisted extraction of potentially toxic lead metal ion from aqueous system using imidazolium-based ionic liquids as sole extracting agent followed by the application of salting-out agents to reduce the release of IL cations in aqueous phase offers great potential for practical application.