Concentration of PGMs from spent automobile catalyst combined by quenching, crushing and surface grinding

Several million spent catalytic converters are disposed annually worldwide and each containing about 0.5-1g of platinum and 1-2g of all the platinum group metals (PGMs), then, it is fairly significant to recover PGMs from the spent automobile catalyst. The PGMs' recovery is a proven technology, including pyro- and hydrometallurgical methods, and the highest recovery can achieve approx. 98 wt.% by acid-leaching method, but these recycling technology seems to be too highly energy-consuming. Since PGMs are distributed only in coat layer in spent catalyst, it is of great significance to enrich the coat layer with some physical methods as a pretreatment. In this paper, according to the double-deck structure of the catalyst and the different properties of the two main compositions, alumina-ceria phase of coat layer and cordierite phase of substrate, the concentration of the coat layer was investigated by combining three kinds of physical separation technologies, heating-quenching, crushing and surface grinding. In the first stage, thermal stress could generate between the two phases by thermal expansion difference, to produce fractures in the thinnest part of coat layer and micro-cracks in coat layer and at the interface of coat layer and cordierite substrate. The second stage of crushing, by jaw and roll crushers, could break dominantly the coat layer and the third stage of surface grinding, carried out by attritor, promoted further separation and concentration of coat layer from the substrate. We also improved the attritor grinding by adding a new lift-arm to the cell for achieving better mobility of sample particles in the selective surface grinding.