Application of hydrophobic extractant in aqueous two-phase systems for selective extraction of cobalt, nickel and cadmium

This work developed a new and efficient method of extracting and separating Co(II), Ni(II) and Cd(II) in aqueous two-phase systems (ATPS) composed of triblock copolymer (L64) + Na2C4H4O6 + water and L64 + Li2SO4 + water using the hydrophobic extractant 1-nitroso-2-naphtol, which complexes the metal ions and partitions in the triblock copolymer micelles in the ATPS top phase. Metal extraction from the salt-rich phase to the copolymer – rich phase is strongly affected by the fine-tuning of the following parameters: amount of added extractant, type of electrolyte, pH, and tie-line length. Excellent separation factors (Si,j) between the metals were obtained at pH = 3.00 (SCo,Cd = 1550 and SNi,Cd = 16,700) and pH = 1.00 (SCo,Ni = 826). In the interference study, Co(II) was selectivity extracted in the top phase in the presence of Ni(II) and Cd(II) in a concentration of up to 20 times the cobalt level in the system.

► Excellent separation factors for Co and Ni, and Co and Cd were obtained.
► Electrolyte nature and pH affect the ions separation in aqueous two-phase system.
► Aqueous two-phase system is a green technique and low cost for metal separation.
► It was demonstrated an efficient liquid-liquid extraction without organic solvent.
► It was demonstrated an efficient extraction applying a hydrophobic extractant.