Deep eutectic solvents based on aliphatic alcohols and salicylaldoxime in the extraction of Ni and Co ions

Currently, a pressing challenge is the development of new extraction systems that meet increasingly stringent environmental requirements and allow for more selective extraction of valuable components from complex mixtures. Deep eutectic solvents, which exhibit lower volatility and fire hazard, represent a promising new class of extractants. A particularly interesting feature is the ability to influence the extraction properties of the first component (often an existing extractant) through the careful selection of a second component, which influences the strength of the component interactions and determines the physical properties of the extraction mixture.

This paper presents new deep eutectic solvents based on salicylaldoxime and aliphatic alcohols (dodecanol and decyl alcohol).

Phase diagrams of the proposed two-phase systems were constructed, and the formation of deep eutectic solvents was confirmed. The interaction of the components was studied using 1H NMR and IR spectroscopy, and the formation of hydrogen bonds between the components was established. The proposed eutectic solvents were tested as extractants for Ni and Co ions from chloride solutions. The proposed HDESs were shown to yield higher Ni and Co ion recovery than salicylaldoxime at the same concentration in kerosene, demonstrating the possibility of influencing extraction properties. The mechanisms for nonferrous metal ion extraction from chloride solutions were established. Furthermore, the recovery of Co(II) using decyl alcohol-based HDES was higher than that of dodecanol-based HDES, while the opposite was true for Ni(II), opening the possibility of adjusting selectivity using a second component.