Highly Effective Extraction of Ruthenium from Hydrochloric Acid Solutions with a Protic Ionic Liquid Trioctylammonium Chloride

Abstract

Extraction of ruthenium(III) from hydrochloric acid solutions was investigated at 25°C by using a protic ionic liquid, trioctylammonium chloride ([HTOA]Cl), as an extraction solvent. Extraction percentages of more than 99% were obtained under the following conditions: volume ratio of aqueous to ionic liquid phase = 1; shaking time ≥ 12 h; aqueous HCl concentration (CHCl) = 4.0 mol/L. The D vs. CHCl plot shows a bell-shaped curve with the maximum D = 106 at CHCl = 4.0 mol/L. Several other ionic liquids were also examined as extraction solvents, and trihexyltetradecylphosphonium chloride ([THTDP]Cl) was found to have a higher extraction efficiency (D = 8 × 102 at CHCl = 4.0 mol/L) than [HTOA]Cl. By using 1.0 mol/L aqueous thiourea as a stripping solution, 100% of the metal was back-extracted from [HTOA]Cl, whereas only 21.4% was back extracted from [THTDP]Cl. The possibility of extraction separation of ruthenium(III) from other metals was also investigated.