The use of hydrophobic deep eutectic solvent dodecanoic acid/menthol as a sustainable diluent for the continuous extraction process of Fe and Ti separation

Hydrophobic deep eutectic solvents (HDES) have long been used for the extraction of metal ions from aqueous systems. This study proposes the use of HDES composed of dodecanoic acid and menthol as a diluent for tributyl phosphate (TBP), which serves as the extractant. The results demonstrate that the extraction system developed remains stable across a broad range of TBP concentrations and possesses excellent physical properties, making it suitable for laboratory-scale extraction equipment. By examining the extraction of iron and titanium ions, key dependencies of extraction efficiency were identified as varying acidity levels, volume ratios, initial metal concentrations and conditions for effective stripping. Notably, the efficiency of the extractant remained unchanged after ten cycles of extraction and stripping, particularly for titanium ions extracted from 10 mol/L hydrochloric acid. This indicates the chemical stability of the proposed extraction system. A continuous separation process for iron and titanium was successfully implemented on laboratory extraction equipment using liquid pseudomembranes, achieving an efficiency greater than 95 % of the theoretical maximum. These findings suggest that HDES have significant potential for use as non-volatile, non-combustible and renewable solvents in extraction processes.