Selective Separation of Pd, Pt, and Rh from Wastes Using Commercial Extractants for the Sustainable Development of Critical Metals Management

This paper presents the results of research on the selective separation of palladium, platinum, and rhodium from waste solutions using commercial organic extractants such as Mextral 63H and trioctylamine. The research was carried out on a real waste solution, containing low concentrations of platinum group metals and significant amounts of base metals such as copper, iron, chromium, and nickel. It was found that a 20% solution of Mextral 63H in toluene selectively extracts over 99% of Pd, while a 10% solution of trioctylamine effectively extracts both Pd and Pt with a yield of over 98%. Effective stripping agents were also selected for the obtained Pd and Pt extracts: 2 M thiourea solution for Pd and diluted solutions of nitric and perchloric acids for Pt. The research allowed the development of a technological scheme enabling the separation of all three platinum group metals by selective extraction of Pd and then Pt, while Rh remains in the raffinate after both extraction stages. The proposed model, developed on the basis of results obtained for a real solution, assumes selective recovery of palladium, platinum, and rhodium from such solutions, which can find application in the precious metals industry. Moreover, the developed technology is in line with the sustainable development of the critical metals economy.