Dissolution of platinum in catalyst materials using hydrochloric acid: A new method based on the use of complex oxides

Platinum group metals (PGMs) are used widely in various applications, including as environmental catalysts. Since PGMs are rare and expensive, they are recycled after being recovered. Currently, PGMs are recovered, after a pyrometallurgical step that upgrades the concentration, by dissolving in strong acids containing toxic oxidizing agents like aqua regia. To avoid the use of such toxic agents, we have proposed a new route to dissolve PGMs in hydrochloric acid (HCl) using complex oxides. In the present study, we used this new process to dissolve Pt in supported metal catalysts. Complex oxides of Pt were prepared by calcining mixtures of Pt/Al2O3 and alkali metal salts at 600-800 °C in air. These were then dissolved in 12 M HCl. The results showed that the Pt in the calcined samples dissolved readily in HCl and that the Pt solubility was nearly 100% under the appropriate preparation and dissolution conditions. We also confirmed that the new process is suitable for leaching PGMs from spent automotive catalysts.