Studies on liquid/liquid extraction of copper ion with room temperature ionic liquid

Room temperature ionic liquids are regarded as "Green solvents" for their nonvolatile and thermally stable properties. They are employed to replace traditional volatile organic solvents in organic synthesis, solvent extraction, and electrochemistry. In this work, a water immiscible room temperature ionic liquid, 1-butyl-3-methylimidazoliurn hexafluorophosphate [C(4)mim][PF6], was used as an alternative solvent for liquid/liquid extraction of copper ions. Metal chelators, including dithizone, 8-hydroxyquinoline, and 1-(2-pyridylazo)-2-naphthol, were employed to form neutral metal-chelate complexes with copper ions so that copper ions were extracted from aqueous solution into [C(4)mim] [PF6]. The parameters that affect the extraction of copper ions with this biphasic system were investigated. The extraction behavior in this novel biphasic system is shown to be consistent with that of traditional solvents. For example, the extraction with this biphasic system is strongly pH dependent. So, the extraction efficiency of coppers ion from an aqueous phase can be manipulated by tailoring the pH value of the extraction system. Hence, the extraction, separation and preconcentraction of copper ions can be accomplished by controlling the pH value of the extraction system. It appears that the use of ionic liquid as an alternate solvent system in liquid/liquid extraction of copper ions is very promising.