Synchronous extraction of Pt, Zr and Ce from spent catalysts via SoG-Si scraps melting collection by regulating Si reduction based on a new fluorine-containing slag

Abstract

Recycling the rare and precious metals from spent catalysts is critical for the sustainability of the petrochemical and automotive industries and fulfilling to close rare and precious metals materials loops. A major challenge is to extract oxidized rare earth and rare metals while collecting platinum group metals (PGM) for the widely used iron and copper smelting collection. Here, a new method for one-step extraction of Pt (PGM), Ce (rare earth metal) and Zr (rare metal) from spent petrochemical catalysts has been proposed based on collaborative melting of solar grade silicon (SoG-Si) scraps. In this process, Si serves as both a reducing agent and collector, which can reduce the oxidized Ce and Zr to metallic elements, and also collect the reduced Ce and Zr together with Pt. Through thermodynamic calculations and experimental exploration, it was demonstrated that Si can effectively reduce zirconium cerium oxide compared to traditional methods using Fe, Cu, and C. Subsequently, a CaO-Al2O3-SiO2-MgO-CaF2 slag system containing fluorine was developed by adjusting slag basicity and the ratio of silicon to slag, which can greatly improve the process of Si reduction of metal oxides. Under this optimized slag system, maximum recoveries of Ce and Zr reached 79.98% and 95.30% respectively, while Pt recovery remained high at 92.08%. Finally, Pt, Ce and Zr in the obtained Si alloy were well separated through a stepwise acid leaching process. This method offers a promising new avenue for the green, clean, and efficient collaborative processing of petrochemical/automotive catalyst and SoG-Si scraps, and also helps close rare and precious metals materials loops.