While public attention is now focused on the electrification of automobiles, the market share EV and HBV was just 9 % worldwide in 2021.

Accordingly, conventional vehicles are still the main vehicles in use, many of which use catalytic converters to post-combust exhaust gases. Platinum group metals, so-called PGMs, are used for this chemical process and offer great potential for recycling due to their value.

Platinum, palladium and rhodium are particularly suitable for the catalytic reaction of exhaust gases and are therefore preferably used on the washcoat. This is a mixture of different carrier oxides that enables the PGMs to be dispersed over as large a surface area as possible. Platinum group metals have been classified as critical raw materials by the European Union since 2011, which makes their recycling even more important. [1]

Pyrometallurgical processes with subsequent hydrometallurgical recovery represent the state-of-the-art for recycling those valuable platinum group metals. Nevertheless, the high-melting components of the washcoat, such as silicon carbide, lead to an increased energy requirement for the melting process. This study aims at the simultaneous smelting of catalytic converters and waste printed circuit boards (PCBs). The circuit boards serve as a source of low-melting ceramics for the conversion of the carbides and contain copper, which serves as a collector metal for the precious metals.

PCBs represent the most valuable part of electronic scrap, and their production has increased constantly by 41% since 2007 [2]. Additives, generally used in this process, have been substituted by using PCBs for the pyrometallurgical recycling process of spent catalytic converters thus represents a promising opportunity for improving the circular economy of both material streams. Nevertheless, the synergies between these two material streams in the smelting process need to be investigated.

Various formulations of feed mixtures were simulated by FactSage® [3]. The aim of the simulation was to create a low-melting slag from the Al2O3-SiO2-CaO system. Experimental trials in a laboratory scale electric arc furnace were carried out successfully and achieved recovery of platinum from spent catalysts of up to 98,5%. Furthermore, a defined phase separation has been achieved, which ensures an efficient removal of slag from the CuSi collection phase.

[1] “Global electric vehicle sales up 109% in 2021, with half in Mainland China” from 14th of February 2022, Low, J., Amberkar, A. www.canalys.com

[2] “So viel Elektronik Abfall produzieren wir”. Statista GmbH. 2019. URL: https://de.statista.com/infografik/20143/elektronik-abfaelle-von-haushalten/

[3] C. W. Bale, E. Bélisle, P. Chartrand, S. A. Decterov, G. Eriksson, A.E. Gheribi, K. Hack, I. H. Jung, Y. B. Kang, J. Melançon, A. D. Pelton, S. Petersen, C. Robelin. J. Sangster, P. Spencer and M-A. Van Ende, FactSage Thermochemical Software and Databases - 2010 - 2016, Calphad, vol. 54, pp 35-53, 2016 <www.factsage.com>