Recovery of platinum from spent automotive catalytic converters by leaching with aluminium-based salts solutions

abstract

The increasing global demand for metals has intensified mining activities, raising serious environmental concerns. Platinum group metals (PGM), classified as critical raw materials (CRM) by the European Union, are essential to modern industries, particularly for automotive catalytic converters. Recycling PGM from spent automotive catalytic converters (SACC) represents a sustainable and circular economy strategy, reducing the dependence on primary mining. In this study, a new hydrometallurgical process was developed for PGM recovery from SACC using an aqueous solution of AlCl3.6H2O and Al(NO3)3.9H2O which offers a greener alternative to the harsh aqua regia. A real SACC from a diesel vehicle was used, following its characterization and pretreatment. The characterization confirmed that Pt was the only measurable PGM present in its composition. Key leaching operational parameters, including reagents and solid-to-liquid (S/L) ratios, temperature, and contact time, were optimized, with temperature identified as the critical factor for Pt leaching. Under optimal conditions, the singlestep leaching process demonstrated high efficiency, achieving 94 % of Pt extraction. The selective separation of Pt was achieved using the Ambersep 900 (R) anion-exchange resin, followed by Pt elution with a thiourea solution. The process was successfully scaled up 60-fold, demonstrating leaching media reusability over five cycles without loss of efficiency and achieving a Pt concentration of 418 mg.L-1. The resin adsorbed 97 % of Pt, with 96 % recovery during the desorption step, finally obtaining Pt isolated. A preliminary cost analysis highlights the economic viability of this acid-free recovery method.

keywords

GROUP METALS; ADSORPTION; DISSOLUTION; PALLADIUM(II); GOLD(III); PD

subject category

Engineering

authors

Braga, FN; Coelho, A; Carreira, ARF; Sosa, FHB; Schaeffer, N; Passos, H; Coutinho, JAP

Groups

G4 - Renewable Materials and Circular Economy

Projects

Collaboratory for Emerging Technologies, CoLab (EMERGING TECHNOLOGIES)

Recovery and separation of platinum group metals and rare earth elements from spent automotive catalytic converters (PlatILPlus)

CICECO - Aveiro Institute of Materials (UIDB/50011/2020)

CICECO - Aveiro Institute of Materials (UIDP/50011/2020)

Associated Laboratory CICECO-Aveiro Institute of Materials (LA/P/0006/2020)

Hydrophobic Eutectic Solvents for Tailored Metal Separation and Recycling (DESignSX)

acknowledgements

This work was financially supported by national funds through FCT - Fundaca o para a Cie ncia e a Tecnologia, I.P., within the scope of the project PlatILPlus (2022.04478.PTDC, DOI: 10.54499/2022.04478. PTDC) . This research was also supported by Fundaca o para a Cie ncia e a Tecnologia, I.P./MCTES through national funds: UID/50020 of LSRE-LCM-Laboratory of Separation and Reaction Engineering - Labora-tory of Catalysis and Materials; ALiCE, LA/P/0045/2020 (DOI: 10.54499/LA/P/0045/2020) ; and CICECO-Aveiro Institute of Materials, UIDB/50011/2020 (DOI: 10.54499/UIDB/50011/2020) , UIDP/50011/2020 (DOI: 10.54499/UIDP/50011/2020) and LA/P/0006/2020 (DOI: 10.54499/LA/P/0006/2020) . This work was co-funded by the European Union (ERC, DESignSX, 101116461) . Views and opinions expressed are however those of the authors only and do not necessarily reflect those of the European Union or the European Research Council. Neither the European Union nor the granting authority can be held responsible for them. F.H.B. Sosa, A. R.F. Carreira and F. Braga acknowledge FCT for the researcher contract CEECIND/07209/2022 (DOI: 10.54499/2022.07209.CEECIND/CP1720/CT0019) and the Ph.D. grants SFRH/BD/143612/2019 and 2023.01749.BD (DOI:10.54499/2023.01749. BD) , respectively. The authors also acknowledge Valorcar - Sociedade de Gesta o de Veiculos em fim de Vida Lda. for providing the spent automotive catalytic converters.