Integrated Ion Exchange and Liquid-Liquid Extraction Process for the Separation of Platinum Group Metals (PGM)

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Abstract
A process for concentration and separation of platinum group metals (PGM) by a combination of ion exchange and liquid-liquid extraction is presented. First the PGM metals are dissolved by HC1/C11 and then passed through an isothiouronium anion exchange resin, where specific absorption occurs. The thiourea eluate from the resin is converted to the chloride complexes. Further hydrolysis (conditioning) yields an aqueous feed to a liquid-liquid extraction step, with Alamine-336. Platinum and palladium are very well extracted, while most of the other PGM are rejected in the aqueous phase. The liquid-liquid extraction can be used by itself, if the level of the base metals does not exceed the concentration of the PGM ions. Platinum and palladium are now separated from each other by the selective stripping of palladium with thiourea, and platinum with thiocyanate. The paper discusses the extraction chemistry of all the steps, and provides also experimental pilot-plant results.
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