Extraction of some metals from aqueous solutions using ionic liquids

In this study, the aqueous two-phase system was developed for the selective extraction of trace metal ions found in environmental water samples. The copper (II), nickel (II), zinc (II) and cobalt (II) ions found at trace level in environmental water were preconcentrated by the novel aqueous two-phase system and determined using flame atomic absorption spectrometry. This aqueous two-phase system is achieved using ionic liquid and inorganic salt. The 8-hydroxyquinoline ligand for metal-complex formation with metal ions in aqueous phase and triton X-100 surfactant for phase formation were used. Ionic liquids with three different cationic groups (phosphonium, ammonium and imidazolium) having bromide as anion group and potassium dihydrogenphosphate as inorganic salt were used. The amount of ionic liquid, type and amount of salt, amount of ligand, complexation pH and amount of surfactant amount were investigated one by one to optimize the novel aquoeus two-phase system. Recoveries with the studied all ionic liquids as 75 mg were found over 85 percent. The effect of complexing pH was investigated in the range of 3-9 and the best extraction efficiency was obtained at pH 7. Optimum ligand concentration was determined as 5x10-4 mol/L. The optimum amount of triton X-100 surfactant was determined as 100 mg. Recovery was obtained in the range of 85-100 percent for all ionic liquids. The volume of ionic liquid rich upper phase was in the range of 250-700 μL. Linear ranges for Cu(II) and for Ni(II), Zn(II) and Co(II) were in the range of 20-500 ppb and 50-500 ppb, respectively. LOD and LOQ values for all studied metal ions were found as 11-17 ppb and 44-54 ppb, respectively. The developed method has been successfully applied to tap water, ground water, sea water samples. The accuracy of the method was evaluated by spiking 0.1 mg/L and 0.3 mg/L mix metal ion solution (copper (II), nickel (II), zinc II) and cobalt (II)) into real samples, and the recoveries were obtained within 65-104 percent.