Extraction of Platinum Group Metals from Spent Catalyst Material by a Novel Pyro-Metallurgical Process

Abstract

The extraction of platinum group metals (PGM) contained in waste automobile catalyst monolithic honeycomb was investigated by a novel approach that combines a pyro-metallurgical and electrolysis step. The first step aims to both up-concentrate the amount of PGMs by using a metal collector, as well as to prepare the conductive material to be used as anode in the electrolysis step. The electrolysis step is carried out in a molten chloride electrolyte, where the PGMs remain as metallic residue, and the refined metal is further reused in the pyro-metallurgical step. Optimization of the pyro-metallurgical process led to 82–100% metal recovery rates, while the PGM recovery rates were close to 100%. Furthermore, the electrolyte composition and working temperature, as well as cell design of the subsequent electrolytic method, were adjusted. The process was assessed in a lab-scale electrolysis reactor, where PGMs could be extracted selectively at a current efficiency of around 70%.