A review on the recycling processes of spent auto-catalysts: Towards the development of sustainable metallurgy.

Spent auto-catalysts are considered as promising platinum group metals (PGMs) resources based on their rapidly increasing demand along with the underlying uncertainty of the sustainability and long-term availability of PGMs. Recycling spent auto-catalysts presents attractive advantages, particularly for the conservation of primary resources reserves, and for the reduction of negative environmental impact due to exploitation. PGM reclamation is the major aim of recycling operations despite their minor concentration in spent auto-catalysts, which implies that the remaining materials are disposed of as unwanted solid waste after the extraction process. This poses a genuine challenge, as well as a motivation to develop recycling processes for spent auto-catalysts capable of recovering all components/valuable metals, while moderating environmental pollution and global warming. The focus herein involves the description of the available technologies, including pyro- and hydro-metallurgical processes, to recover PGMs from spent auto-catalysts, and specifically an analysis of the developmental trends in recycling methods to ensure "sustainable metallurgy".