Separation of Co(II) and Ni(II) from aqueous solutions by bis(2,4,4-trimethylpentyl)phosphinic acid (Cyanex 272) using trihexyl(tetradecyl)phosphonium chloride (Cyphos IL 101) as solvent

This paper focuses on the separation of Co(II) from Ni(II) by liquid-liquid extraction using bis(2,4,4-trimethylpentyl)phosphinic acid (Cyanex 272) as extractant and trihexyl(tetradecyl)phosphonium chloride (Cyphos IL 101) as diluent. The influence of the temperature, the concentration of Cyanex 272 and the pH of the aqueous phase have been studied. The use of 0.5 mol L− 1 Cyanex 272 in Cyphos IL 101 at 323.15 K leads to a fast and efficient extraction of Co(II) from chloride aqueous solution at pH 6 (90% Co(II) extracted) without significant extraction of Ni(II). Furthermore, 100% Co(II) can be stripped from Cyanex 272 + Cyphos IL 101 by using 0.1 mol L− 1 sulphuric acid at 298.15 K.