Recovery of Platinum Group Metals from Spent Catalysts Using Electroless Nickel Plating and Magnetic Separation

Abstract

This study demonstrates a new process for physically recovering platinum group metals (PGMs) directly from spent automobile catalysts. Automobile catalysts mostly consist of a honeycomb-structured ceramic substrate coated with a porous catalyst layer supporting fine particles of Pt, Pd, and Rh. In the proposed process, in order to magnetically separate and concentrate the PGMs, ferromagnetic Ni is deposited on the PGM particles (or the catalyst layer) using an electroless plating technique. Experiments were performed using samples that simulated an automobile catalyst. Using the electroless plating process, Ni could be coated on the porous catalyst layer without requiring complicated pretreatments such as sensitization and activation. Furthermore, the PGMs (Pt, Pd, and Rh) could be extracted and concentrated in the form of a magnetic powder through magnetic separation performed after Ni deposition and subsequent pulverization. Thus, the proposed physical concentration process is feasible and effective, and this process can be extended for making the recycling of automobile catalysts more efficient and environmentally friendly.

Fig. 1 Mechanism of the novel process for physically separating PGMs from spent catalysts. Ferromagnetic Ni is deposited on the PGM particles or the catalyst layer using the electroless plating technique. A heat treatment is performed as needed in order to improve the adhesion of the Ni deposit. Then, the Ni-deposited catalysts are pulverized and magnetically separated. This process is expected to concentrate PGMs in the magnetic powder and to remove the ceramic components in the form of the nonmagnetic powder.