Hydrometallurgical Recovery of Platinum Group Metals

Platinum group metals (PGMs)—comprising platinum, palladium, rhodium, iridium, ruthenium and osmium—are critical to catalytic applications in automotive exhaust treatment, chemical synthesis and emerging energy technologies. Their natural scarcity and high economic value have driven the development of recycling strategies that recover PGMs from secondary resources such as spent automotive catalysts and industrial residues. Hydrometallurgical routes offer an environmentally friendlier alternative to energy-intensive pyrometallurgy, employing aqueous chemistry to dissolve metal species and subsequently separate them in concentrated form. Key operations include oxidative leaching to convert PGM solids to soluble chloride, nitrate or sulphate complexes, followed by selective recovery via solvent extraction, ion exchange or precipitation. Advances in reagent design, process intensification and phase-transfer media have improved recovery yields, reduced acid consumption and minimised co-dissolution of base metals. These innovations enhance global supply security, lower the environmental footprint of metal production and support circular-economy principles for strategic materials.

Research from Nature Portfolio

Recent studies have focused on bespoke molecular extractants to achieve high selectivity for individual PGM species under strongly acidic conditions. One series of pincer-type ligands demonstrated near-quantitative extraction of palladium(II) from mixed chloride and nitrate media, outperforming commercial reagents in terms of loading capacity, acid stability and reusability. Detailed spectroscopic analysis revealed the coordination mode and extraction mechanism, paving the way for tailored ligand frameworks. Another effort introduced a thioamide-modified calix[4]arene macrocycle that achieved >99.9% selective uptake of palladium(II) from simulated automotive catalyst leach liquors. This extractant combined rapid kinetics with high acid resistance and could be recycled over multiple cycles, illustrating the potential for scale-up in industrial recovery operations.

Hydrometallurgical Recovery of Platinum Group Metals publication trend

The graph below shows the total number of articles in hydrometallurgical recovery of platinum group metals across all publications each year (not limited to Nature Index journals).

Technical terms

Hydrometallurgy: The branch of extractive metallurgy using aqueous solutions to recover metals from ores or recycled materials.

Leaching: A process in which soluble metal compounds are dissolved from a solid matrix by contact with an acidic, alkaline or oxidising solution.

Solvent extraction: A separation technique where metal ions in an aqueous phase are transferred into an immiscible organic phase containing specific ligands or extractants.

Supported ionic liquid phases (SILPs): Hybrid materials in which ionic liquids are immobilised on solid supports to combine the selectivity of ionic liquids with the handling convenience of solids.

Extractant: A molecule or material capable of selectively binding and removing target metal ions from a solution, often via coordination or ion-exchange mechanisms.

References

1. Platinum Group Metals: A Review of Resources, Production and Usage with a Focus on Catalysts. Resources (2021).
2. Hydrometallurgical recovery of platinum-group metals from spent auto-catalysts – Focus on leaching and solvent extraction. Separation and Purification Technology (2022).
3. Synthesis of pincer-type extractants for selective extraction of palladium from PGMs: An improved liquid-liquid extraction approach to current refining processes. Scientific Reports (2017).
4. Rapid and selective recovery of palladium from platinum group metals and base metals using a thioamide-modified calix[4]arene extractant in environmentally friendly hydrocarbon fluids. Scientific Reports (2018).