Recovery of platinum, palladium and rhodium from industrial process leaching solutions by reactive extraction

The selective reactive extraction of platinum, palladium and rhodium from a 6 M HCl collector solution of spent autocatalysts and from a model solution containing large amounts of iron and nickel was investigated. Most of the Fe and Ni was removed by pretreatment. Pd was selectively extracted from the HCl solution. PI, Rh, and the rest of the Fe and Ni remained in the raffinate. The re-extraction of Pd was performed with thiosulfate solution after the removal of Fe and Ni by scrubbing with dilute HCl. Pt was extracted from the raffinate with a solution of Hostarex, decanol and Exxsol, scrubbed with 0.1 H Cl to remove the traces of Fe and Ni, and then Pt was re-extracted with thiosulfate solution. Raffinate of the second extraction contained Rh and a small amount of base metals. Rh was recovered in an ion exchange process. This approach was applied in pilot-plant-scale investigations. The removal of Fe was performed with ion exchange and the separation of Pd by extraction with Cyanex 471 x, tributylphosphate and p-nonylphenol, scrubbing the organic phase with 0.01 M HCl and re-extraction of Pd with 1 M thiosulfate. These processes were performed in a continuous operation. (C) 1997 Elsevier Science B.V.