A sustainable hydrometallurgical strategy for recycling efficiently platinum from spent reforming petroleum catalyst

Platinum (Pt) is one of the most precious metals with a variety of unique industrial applications, particularly in catalytic reactions, being its recovery, after use, essential. Therefore, this work proposes a simplified hydrometallurgical strategy to recover Pt efficiently from the original (no milling) spent petrochemical Pt catalyst using an economical and environmentally sustainable process. To that end, the effectiveness of a two-step workflow constituted by one microwave-assisted leaching step using a mixture of hydrochloric acid (HCl) and hydrogen peroxide (H₂O₂) followed by one ion-exchange purification step was developed and optimized. It was found that complete dissolution of Pt plus aluminum (Al) and iron (Fe) from the roasted original size catalyst was achieved after microwave-assisted leaching with 25% (v/v) HCl and 2% (v/v) H₂O₂ during 2 cycles of 60 s. Furthermore, a strong anionic exchange (Purogold™ A194) resin used for subsequent selective purification of Pt from Al and Fe was capable of effective separation of the metals: Pt in the eluate presented a purity of 98.1%, while Al, in the raffinate, presented a purity of 99.8%. In summation, it can be concluded that the overall process is a potentially good addition to a more circular economy as it manages to recover high-quality Pt for being reused as well as other by-products, whilst minimizing the consume of reagents, leaching time (and, thus, energy), and environmental impacts.