Sustainable Recovery of Platinum Group Metals via Oxysalt Phase Reconstruction and Subsequent Deep Eutectic Solvent Leaching

Abstract

The recycling of platinum group metals (PGMs) underpins sustainable development across semiconductors, new energy devices, and catalytic materials. Efficiently enriching and extracting these sparsely distributed PGMs from solid wastes such as spent catalysts still pose a significant challenge. Here, a novel strategy coupling PGM mineral phase reconstruction with mild deep eutectic solvent leaching is proposed. The inert metallic PGMs are transformed into soluble oxysalt phases by carbonate thermal activation. A mixed carbonate mixture (Na2CO3/Li2CO3 = 5:1, total dosage 15 wt %) serves as a cation−oxygen donor for thermal activation at 800 °C for 1 h under flowing air. Subsequent selective leaching at 80 °C over 1 h with a mild deep eutectic solvent recovers 80.6% of Pt, 85.3% of Pd, and 76.0% of Rh, in stark contrast to the nearly zero recovery via direct leaching. This design eliminates traditional reliance on aqua regia and realizes the selective recovery of PGMs. Combined economic and environmental assessments validate the superior performance of the developed process. Overall, this work offers a viable and sustainable pathway for recycling supported spent PGM catalysts, in alignment with circular economy principles.