Efficient Recovery of Platinum Group Metals from Spent Automotive Catalysts Using Iron Smelting Method by Optimizing Slag Composition at Low Temperature

Spent automotive catalysts (SACs) are the most important secondary resource for platinum group metals (PGMs). Due to the complex physicochemical properties and low concentration of SAC, it is very difficult to recover Pt, Pd, and Rh. The technology of using smelting iron to recover PGMs has the advantages of a simple process and large-scale production. The rheological behavior of slag is an important influencing factor in the recycling process. In this paper, the principle of slag design is proposed, and CaO/SiO₂ mass ratio and B₂O₃ content are used as parameters to adjust the composition of the slag. The viscosity of slag was measured by the rotation axis method, and the structure of the slag was characterized by FTIR and Raman spectroscopy. The influence on the rheological properties and structure of slag was studied to optimize the smelting process. The optimized composition of the slag is 5.10 wt.%CaO-43.86 wt.%SiO₂-9.40 wt.%Al₂O₃-5.64 wt.%MgO-6.00 wt.%B₂O₃. In the reduction melting experiment, the recovery rate of PGMs reached 99.8%. This, furthermore, avoids the generation of ferrosilicon (FeSi), providing a reference for the effective recovery of PGMs.