Extraction of transition metals using a trioctylamine/geraniol eutectic solvent: a green route for metal processing

The development of hydrometallurgical methods for the extraction of transition metals requires the search for efficient and environmentally friendly alternatives to traditional organic solvents. Hydrophobic eutectic solvents represent an alternative to flammable and toxic extractants and have already proven themselves in metal processing within hydrometallurgy. In this work, the extraction of Fe, Cu, Mn, and Ni using a hydrophobic eutectic solvent based on trioctylamine and geraniol was studied, demonstrating high selectivity and potential for green metal processing.

The proposed eutectic solvent was prepared by mixing the required amounts of amine and geraniol at a component ratio of 1:3 for 15 minutes at 60 °C in a thermostatic shaker. Extraction was carried out at room temperature in plastic centrifuge tubes with an organic-to-aqueous phase volume ratio of 1:5. The initial concentration of metals was 0.01 mol/L.

The interfacial distribution of Fe, Cu, Mn, and Ni ions in the system based on the proposed eutectic solvent was determined: at a hydrochloric acid concentration of 3 mol/L, the distribution coefficients of the metals were 331.35, 1.9, 0.6, and 0.33, respectively. The separation factors Fe/Me were calculated, amounting to 174, 552, and 1004 for copper, manganese, and nickel, respectively. The dependence of the metal ion distribution coefficients on the hydrochloric acid concentration in the solution was established. The results show that with increasing acid concentration, the extraction efficiency increases for Fe and Cu, while for Mn and Ni it remains practically unchanged.

The conducted study demonstrated the possibility of efficient separation of metal ions in their joint presence using the trioctylamine/geraniol eutectic solvent.