Novel Task Specific Ionic Liquids to Remove Heavy Metals from Aqueous Effluents

Abstract

Task Specific Ionic Liquids (ILs) were generated by association between a cationic ester derivative of betaine and coordinating inorganic anions such as dicyanamide (Dca−), chlorosalycilate (ClSal) and saccharinate (sac). Extraction of Cu(II), Ni(II), Co.(II), Pb(II) and Cd(II) from water was performed with these ILs at room temperature. Our results show that ionic liquid with Clsal anions have a high extraction efficiency towards Cu(II), Ni(II), Cd(II), and Pb(II), whereas dicyanamide ionic liquid may extract efficiently Cu(II), Ni(II) Co.(II) and Cd(II). Ionic liquids with saccharinate anions are selective of Cd(II) ions. The extraction mechanism has been studied by the determination of the coextraction of the counter ion of the metal salt. Our results show that the extraction mechanism proceeds via a mixed process involving both cation exchange and ion-pairing. The proportion of which depends on the nature of the cation. The coordination of Cu(II), Ni(II) and Co.(II) in ionic liquid phase was followed by UV-vis spectroscopies. The metal could be back-extracted from the ionic liquid phase with aqueous EDTA solutions. The metal extractability of the ionic liquid after the back-extraction is equivalent to that of the fresh mixture showing that ionic liquid can be reused for several extraction and back-extraction cycles.

Keywords

• ionic liquids
• metal extraction
• liquid-liquid extraction
• back-extraction
• reusability