• Resources Recycling
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• v.15 no.5 s.73
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• pp.3-10
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• 2006

The solvent extraction for the separation of platinum group metals from the leach liquor of spent automotive catalysts has been studied. Tri-n-butyl phosphate (TBP), tri-n-octylamine (TOA) and di-n-hexyl sulfide (DHS) were used as extractants and kerosene as a diluent. The extraction behavior of platinum, palladium and rhodium has been investigated as functions of different kinds of extractants and their concentrations. In addition, the extraction behavior of the major metal impurities such as cerium, lead, iron, magnesium and aluminum has been investigated. Platinum and palladium were extracted with TBP. And platinum, palladium and rhodium were extracted with TOA. Platinum was co-extracted with palladium into the organic phase by solvent extraction using SFI-6 of DHS extractant, but only palladium was selectively extracted with SFI-6R. The selective extraction of palladium with SFI-6R was found better than that with SFI-6, but the kinetics of extraction with SFI-6R was found poor in comparison to SFI-6. The metal impurities extracted simultaneously during the extraction of platinum group metals should be removed in scrubbing and stripping processes. A suitable process has been proposed for the separation of platinum group metals from the leach liquor of spent automotive catalysts. Initially palladium was extracted with SFI-6R, followed by the separation of platinum with TBP or TOA leaving rhodium in the raffinate.

• Proceedings of the IEEK Conference
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• 2001.10a
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• pp.482-488
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• 2001

Platinum group metals (pgm) are useful to many industries such as chemical, dental and medical, petroleum, refining, electrical and electronic, and automotive. Researchers at the South Dakota School of Mines and Technology and PGM Recovery Ltd. have developed jointly an environmentally sound and metallurgically efficient process for extracting these metals from secondary sources. Once these metals have been dissolved in the leach liquor, the individual metals mainly platinum, palladium, and rhodium, should be separated in order to recover the individual metals with high purity. During this investigation, solvent extraction has been chosen as the method used to achieve the separation and extraction of platinum, palladium, and rhodium from the leach liquor. There were three solutions used throughout this procedure: 1) Synthetic solution (200 ppm Pt 80 ppm Pd 20 ppm Rh; 300 ppm Pt, 180 ppm Pd 50 ppm Rh), and 2) Auto catalyst leach liquors (100 ppm Pt, 30 ppm Pd, 20 ppm Rh). The solvents investigated included Lix 84(2-hydroxy-5-nonylacetonphenone oxime in a mixture with 5-dodecylsalicyloxime), Lix 84-I, ACORGA CLX-50 (diester of pyridine 3,5 dicarboxylic acid), and di-hexyl sulfide. The extraction values achieved using ACORGA CLX-50, Lix 84, and Lix 84-I were respectively Pt (25%, 0% 0%), Pd (100%, 99.8%, 95.3%), and Rh (99.1%, 35.5%, 4.25%). The stripping processes for the Lix 84, and Lix 84-I were proven to be more involved than others. The solutions were required to be simultaneously heated and stirred. The percentages acquired through these processes yielded unsatisfactory results. The stripping procedure for the ACORGA CLX-50 was easier to execute, yet the percentage recovered from this process was also unsatisfactory. Overall the di-hexyl sulfide has proved to be the most successful organic for this procedure. The average percent extracted for palladium was excellent with 99.9% - 100% with very little Platinum and rhodium extracted. The ability of stripping palladium in ammonia solution was also found to be excellent.