Extractive Separation of Co/Ni Pair With the Deep Eutectic Solvent Aliquat 336/Timol

This paper presents the results of a study of the physical properties of a hydrophobic deep eutectic solvent (HDES) based on Aliquat 336 and thymol. A solid–liquid phase diagram was built based on the glass temperatures of the Aliquat 336/thymol mixture in different molar ratios. For the first time, the temperature dependences of the density, viscosity, and refractive index of the suggested HDES have been studied. A study of the extraction of Co(II) and Ni(II) ions was carried out under various conditions with HDES Aliquat 336/thymol as an extractant: the influence of the concentration of hydrochloric acid, the concentration of ammonium/lithium/sodium chloride, and the volumetric ratio of phases was studied. The mechanism of the extraction of Co(II) ions by the proposed HDES has been established. Based on the obtained experimental data, it was shown that a Co/Ni pair can be separated from hydrochloric acid solutions with the proposed HDES.