2005•Separation Science and TechnologyRequires access
Liquid‐Liquid Extraction of Ir, Ru, and Rh from Chloride Solutions and Their Separation Using Different Commercially Available Solvent Extraction Reagents
S. Kedari, María Teresa Balaguer Coll, Agustín Fortuny, Elżbieta Góralska, Ana Maria Sastre
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Abstract
The extraction of Ir, Ru, and Rh from their chloride solutions was carried out using different commercially available solvent extraction reagents. The extractants studied were Alamine 300, Alamine 336, Aliquat 336, Cyanex 921, Cyanex 923, Cyanex 471, Cyanex 272, LIX 54, LIX 860N‐I and tributyl phosphate (TBP). The distribution coefficients for the metals were determined under different concentrations of Cl− and H+ ions in the aqueous phase. The extraction data relating to the consecutive steps of stripping the metal species from the loaded organic phase were also recorded. The results showed that more than 90% of the Ir can be extracted using Alamine 300, Alamine 336, and Aliquat 336 when less than 0.2 M Cl− is present in the aqueous phase, and that quantitative stripping of Ir can be performed. For higher concentrations of Cl− in the aqueous phase, Cyanex 921 was found to be the best extractant for Ir, although the mixed extractants such as Alamine 336+LIX 54, Aliquat 336+LIX 54, and Cyanex 921+TBP were also found to be useful for the extraction of Ir from high concentration chloride solutions. For Ru, mixtures of extractants such as Alamine 336+LIX 54 and Aliquat 336+LIX 54 were found to be more effective for extraction, as well as better stripping of Ru was obtained from Ru loaded in such organic phases. The extraction of Rh proved to be difficult, and a maximum of only 31% extraction was achieved using Alamine 300 in the organic phase and a freshly prepared solution of the rhodium chloro complex in 1 M HCl in the aqueous phase. On the basis of these observations, a complete scheme for the individual separation of Ir, Ru, and Rh was proposed and tested with synthetic solutions of these metal chlorides. This resulted also in the development of a method for the separation and recovery of Ir, Ru, and Rh from hydrochloric acid solutions containing a high concentration of Cl− ions.