Extraction of Gold and Palladium from Aqueous Solutions with Ionic Liquids

A possibility of using ionic liquids based on tetraalkylammonium cations and the dicyanamide anion as extractants for the extraction of Au(III) and Pd(II) from aqueous chloride solutions is studied. Three types of ionic liquids with different alkyl chain lengths are synthesized, and the optimal parameters for analyte extraction are determined. Metal extraction is found to be most effective at pH ≈ 7, 50°C, contact time of 8 min, and phase volume ratio of 10 : 1. Recovery exceeded 98% in all studied systems, with maximum recovery characteristic of ionic liquids with the tetraoctylammonium cation. The mechanism for the cation extraction—the formation of ion pairs between an organic cation and complex metal anions—is established. The potential of ionic liquids as more environmentally friendly alternatives to traditional solvents for the extraction of precious metals is confirmed.