CHARACTERIZATION OF EXTRACTED COMPLEXES IN LIQUID-LIQUID-EXTRACTION OF RHODIUM WITH KELEX-100 IN THE PRESENCE OF SNCL2

Mixed Rh-Sn complexes found in aqueous and organic solutions involved in the liquid-liquid extraction of Rh(III) from chloride solutions, also containing SnCl2, with 7-(4-ethyl-1-methyloctyl)-8-hydroxyquinoline (Kelex 100) were characterized through Sn-119 NMR and Raman spectroscopy. At Sn:Rh molar ratios of 3:1 and 12:1, it was found that [(RhCl3)-Cl-III(SnCl3)(3)](3-) and [Rh-I(SnCl3)(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 Rh-Sn complex is found in the aqueous feed and in the fully loaded organic. In addition, it was found that [Rh-I(SnCl3)(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 H2SO4 shows an Rh-Sn complex having a ratio of 5:1 Sn:Rh.