Recovery of Palladium and Platinum Particles Suspended in the Al₂O₃–CaO–SiO₂ Slag Using Copper-Based Extractants at 1723 K

Abstract

Platinum group metals (PGMs) are precious rare metals mined only in a few regions of the world. Recycling PGMs used in automotive catalytic converters is of utmost importance to meet increasing global demand. The Rose process is the main recycling process used in Japan to recover PGMs from spent automotive catalytic converters. The recycling process involves smelting a ceramic structure, in which PGMs are supported, with Cu, Cu₂O, reductants, and fluxes such as CaO and SiO₂.

This study compared the Pd and Pt recovery capability of Cu or Cu₂O as extractants. Pd and Pt particles were simultaneously suspended in Al₂O₃–CaO–SiO₂ molten slag, and the extractant Cu or Cu₂O was added. The concentration of Pd and Pt in the slag as a function of processing time was investigated at 1723 K of the operating temperature in the Rose process, under carbon saturation. The results show that the suspended Pd and Pt particles were combined by collisions in the slag, and the recovery ratio and recovery speed of Pd and Pt suspended particles were higher when using Cu₂O than when using Cu. The Cu₂O dissolved in the slag was reduced to metallic Cu in the slag and alloyed with the suspended PGMs particles to form Cu-PGMs alloys. As a result, the particle size of the PGMs increased and sedimentation motion in the slag is promoted.