Extraction of cobalt (II) using ionic liquid-based bi-phase and three-phase systems without adding any chelating agents with new recycling procedure

The aqueous biphasic system (ABS) based on 1-hexyl-3-methylimidazolium tetrafluoroborate [HMIM] [BF4] and sodium chloride as salting-out agent has been utilized for an efficient extraction of cobalt (II) from neutral media without adding any complexing agents. Effects of different operational parameters, such as initial amounts of system components, the volume and the concentration of cobalt (II), the presence of coexisting ions such as lead (II), cadmium (II), copper (II), manganese (II), zinc (II) and nickel (II), and temperature influence, were extensively investigated. As a third phase, aqueous solutions containing different additives, like NaCl, NaPF6, HCl, Na2SO4, NaH2PO4, were tested. It has been proven that the stripping of the metal complex from the IL phase by a regenerating solution containing chaotropic salt (NaPF6) in three-phase extraction system not only improved the extraction efficiency, but also enabled to regenerate ionic liquid phase. The metallic content has been determined by inductively coupled plasma optical emission spectrometry (ICP-OES).