Characteristics of spent automotive catalytic converters and their effects on recycling platinum-group-metals and rare-earth-elements

Abstract

Numerous spent automotive catalytic converters (SACCs) are being produced annually owing to the increasing number of end-of-life automobiles. Although various methods have been proposed for recycling platinum-group metals (PGMs) and rare-earth-elements (REEs) from SACCs, most achieve low recovery ratios owing to the poor understanding of the characteristics of SACCs. In this study, the characteristics of SACCs and occurrence states, migration, and distributions of elements were in-situ investigated in 3D. The deactivation mechanisms of the automotive catalytic converters (ACCs) and the reasons behind the low PGM recovery ratios were revealed. Interestingly, the typical characteristics of SACCs, such as micro-cracks, blocked channels, molten phases of carrier and coating, molten phase of Fe-PGMs, presence of PGMs oxides, heterogeneous distribution of valuable elements, REE oxides mixed with ZrO2 and Al2O3, were observed in the SACCs. The effects of these SACCs’ characteristics on purchase of SACCs and some methods of recovering PGMs and REEs were discussed, and solutions to the problems were suggested.