Leaching of Pt, Pd and Rh from Automotive Catalyst Residue in Various Chloride Based Solutions

Platinum-group metals (PGM) are important precious metals in many industrial fields. However, their natural resource deposits are strictly limited. Accordingly, their recycling process from wastes and/or secondary resources must be considered. In this study, the leaching of PGM from automotive catalyst residue was performed based on the formation of their chloro-complexes in various concentration of acidic solution. The recovery of platinum, palladium and rhodium from the samples after hydrogen reduction pretreatments was examined in the leaching process by using a mild solution mixture of NaClO–HCl and H2O2 at 65°C for 3 h. Effect of other solution mixtures on the extraction of the precious metals was also compared with NaClO–HCl–H2O2, such as HCl–H2O2 and NaClO–HCl. The optimum condition to dissolve platinum, palladium and rhodium was achieved by the mixture of 3 vol% NaClO, 5 kmol·m−3 HCl and addition of 1 vol% H2O2. The recovery of platinum, palladium and rhodium after 3 h leaching reaches 88%, 99%, 77%, respectively.