Separation of palladium from platinum using synergistic extraction

Abstract

A synergistic effect was observed for the extraction of Pd when a solution containing trace amounts of Pt^IV and Pd^II was extracted with chloroform containing 8-hydroxyquinoline (HQ) and tributylphosphite (TBPI). Proton nuclear magnetic resonance (NMR) spectroscopy and thermogravimetry were used to confirm the composition of the synergistic species extracted. The NMR spectrum indicated that HQ and TBPI were present in a ratio of 1 : 1. From thermogravimetric analysis the extracted species was postulated to be Pd.Q.TBPl.Cl. From these results an extraction mechanism was proposed for the synergistic phenomena observed in these systems. When each extractant was used separately the ratio of the separation of Pd and Pt was found to be approximately 20 : 1. In contrast, the separation ratio increased to ca. 2000 : 1 when a combination of HQ and TBPI was used for the extraction. The proposed method was applied to a synthetic sample solution, the composition of which was similar to that of anode slime obtained from an electrolytic copper refinery. The results indicated that trace amounts of Pd (ca. 5 × 10^–4M) could be separated effectively from equal amounts of Pt.