Extraction separation studies of Rh, Pt and Pd using Cyanex 921 in toluene—a possible application to recovery from spent catalysts

Liquid–liquid extraction of rhodium, platinum and palladium with Cyanex 921 from aqueous hydrochloric acid media has been examined in the absence and in the presence of tin(II) chloride. In order to facilitate the separation of these individual metal ions from their mixtures, the extraction of each metal ion was studied separately, under the influence of variables such as: hydrochloric acid concentration, tin(II) chloride concentration, reagent concentration, equilibration time and stripping agents. Thereafter, the method developed was applied to the recovery of these metal ions from a synthetic solution similar in composition to that expected from the leaching of spent catalysts in 6.0 M hydrochloric acid.