Recovery of Platinum Group Metals from Spent Automotive Catalysts: A Review of Metallurgical and Emerging Methods

Platinum group metals (PGMs) are key components of automotive emission-control catalysts, and spent automotive catalysts (SACs) are their main secondary source. This paper reviews hydrometallurgical, pyrometallurgical, magnetic-separation, biometallurgical, and ionic-liquid/deep-eutectic-solvent (IL/DES) routes and compares them for recovery, selectivity, energy demand, reagent hazard, technology readiness, and scalability, using values re-checked against accessible primary sources. Smelting with Cu- or Fe-based collectors is the only fully industrial route and gives the highest reported recoveries (≈90–99% for Pt and Pd and ≈85–98% for Rh). Hydrometallurgical leaching operates at lower temperature and separates the individual metals but relies on corrosive reagents and dissolves rhodium slowly. Magnetic-separation methods are pre-concentration steps, and biometallurgical and IL/DES routes remain at laboratory scale; their environmental performance has not yet been established by life-cycle assessment. A paired comparison of Rh with Pt and Pd shows that leaching at ≤90 °C typically extracts about 10–60 percentage points less Rh than the best-recovered companion metal, whereas gaps of about 10 points or less are reported for most smelting studies and for some intensified chloride leaching (≥150 °C, alkali calcination, or iron alloying). Integrated flowsheets coupling pretreatment with selective refining remain to be demonstrated at scale and need consistent techno-economic and life-cycle assessment.