Characterization of extracted complexes in liquid–liquid extraction of rhodium with Kelex 100 in the presence of SnCl 2

Mixed RhSn complexes found in aqueous and organic solutions involved in the liquid–liquid extraction of Rh(III) from chloride solutions, also containing SnCl 2 , with 7‐(4‐ethyl‐1‐methyloctyl)‐8‐hydroxyquinoline (Kelex 100) were characterized through 119 Sn NMR and Raman spectroscopy. At Sn: Rh molar ratios of 3:1 and 12:1, it was found that [Rh III Cl 3 (SnCl 3 ) 3 ] 3− and [Rh I (SnCl 3 ) 5 ] 4− , respectively, are the dominant complexes in both the aqueous and organic solutions. These complexes can be quantitatively extracted from the aqueous solutions in less than 1 min contact time via ion‐pair formation with the protonated 7‐substituted 8‐hydroxyquinoline reagent such that for both Sn:Rh ratios, the same RhSn complex is found in the aqueous feed and in the fully loaded organic. In addition, it was found that [Rh I (SnCl 3 ) 5 ] 4− is preferentially extracted over excess free Sn(II). Preliminary characterization of the complex stripped from the 12:1 loaded organic using 1·7 M H 2 SO 4 shows an RhSn complex having a ratio of 5:1 Sn:Rh.