Recovery of platinum group metals from spent automotive catalysts: A review

In the last decades, a worldwide investment in the recovery or substitution of platinum group metals (PGMs) has been financed. PGMs have been classified as critical raw materials (CRMs), thus a circular economy model should be implemented for their effective recovery. PGM recovery from primary ores is expensive, due to low concentrations of their ores (lower than 10 g/tn) and sophisticated processes implicated, while secondary resources have been proven technoeconomically feasible sources for PGM recycling. Secondary resources of PGMs, such as spent automotive catalytic converters, contain considerably higher PGM concentrations than their corresponding ores. It is estimated that spent automotive catalytic converters deliver more than 57% of PGMs’ European supply, being considered a crucial resource for PGM recovery. Novel recovery techniques focus not only on high recovery rates, but also on cost efficiency and environmental protection. From an industrial viewpoint, pyrometallurgy is the dominant recovery technique, hydrometallurgy is secondly chosen and biometallurgy (bioleaching, bioabsorption) is applied for lab-scale recovery -at this moment. In the present review, all major PGM recovery techniques are presented and discussed. Hydrometallurgical processes could gain a foothold in industrial scale recycling, by adopting a direct, sustainable leaching design. Milder leaching conditions, greener solvents and high solid mass leached, are the keys for the hydrometallurgical upscaling.