Separation of Ir(IV) and Rh(III) from mixed chloride solutions by solvent extraction

In order to find an optimum condition to separate rhodium and iridium, solvent extraction experiments were performed from chloride solution by using Alamine336 and TBP as an extractant. Effects of extraction conditions on the separation of both metals were investigated as a function of the concentration of HCl, SnCl2, and extractants. In our system, the concentration of Rh(III) and Ir(IV) were fixed at 0.0005 and 0.00025 M, respectively. In the absence of SnCl2, extraction percentage of Ir(IV) by Alamine336 and TBP was much higher than that of Rh(III) from the mixed solution. However, adding SnCl2 to the mixed solution depressed the extraction of Ir(IV), while the extraction of Rh(III) was increased owing to the reducing action of SnCl2. Extraction order of Rh and Ir by Alamine336 and TBP can be changed by adding SnCl2 to the mixed solution. The highest separation factor was obtained by using Alamine336 in the presence of SnCl2. By utilizing our results, Rh(III) or Ir(IV) can be selectively extracted into Alamine336 or TBP and the choice of either Alamine336 or TBP depends on the concentration of HCl.