Investigation of a novel ionic liquid, Cyphos IL 104 for the solvent extraction of mineral acids

•Solvent extraction of different mineral acids was investigated using Cyphos IL 104.•Extraction stoichiometry of acid by the ionic liquid was analyzed by Job's method.•Stripping of loaded Cyphos IL 104 was examined using distilled water and NaOH.•FT-IR spectra of Cyphos IL 104 were analyzed before/after extraction and stripping.•Extraction of HCl was also investigated in the presence of rare earth metal ions.

A variety of mineral acids is used in metallurgical processes which generate a huge amount of waste solutions containing such acids. Effective recovery of these acids can yield value added products which can minimize health and environmental hazards. The present investigation deals with the use of an ionic liquid as an extractant for the recovery of mineral acids. Extraction behavior of an equimolar concentration (1 M) of different mineral acids such as HCl, H2SO4, H3PO4, HClO4 and HNO3 was investigated using an ionic liquid, “Cyphos IL 104” (trihexyl(tetradecyl) phosphonium bis(2,4,4-trimethylpentyl) phosphinate) ([R4P+][A−]). The stoichiometry of extraction of the acid by the ionic liquid examined by Job's method indicated the involvement of 1 mol of Cyphos IL 104 for the extraction of 1 mol of acid. Loading capacity of Cyphos IL 104 for different acids was particularly investigated. McCabe Thiele plots drawn for the extraction of HCl and HNO3 by using 0.5 M Cyphos IL 104 indicated that two stages are required for complete extraction of 1 M HCl at O/A ratio of 2.2:1, whereas only one stage is required for complete extraction of 1 M HNO3 at O/A ratio of 2:1. Stripping study of loaded Cyphos IL 104 was examined using distilled water and NaOH solution. Regenerated Cyphos IL 104 exhibited similar extraction efficiency as that of virgin Cyphos IL 104. Extraction of hydrochloric acid by Cyphos IL 104 has also been studied in the presence of the lanthanum (III) ions with the aim of processing the leach solutions of rare earths containing resources.

Graphical abstractSchematic diagram of mechanism of extraction of mineral acids with ionic liquid, Cyphos IL 104 (R4P+ A−).Download full-size image