Tuning Palladium and Platinum Leaching Selectivity in Aluminum-Based Salt Systems

The increasing demand for platinum group metals (PGM) has intensified the need for sustainable recycling strategies for spent automotive catalytic converters (SACC). Previous studies demonstrated the potential of aluminum-based salts as alternative lixiviants for platinum recovery.[1] Building on these findings, this work extends their applicability to selective Pd and Pt recovery from SACC. A statistical Design of Experiments (DoE) methodology was employed to evaluate the influence of operational parameters on metal extraction and selectivity. Kinetic studies were subsequently performed under the optimized conditions identified by the DoE analysis. The experimental design enabled the identification of two distinct hydrometallurgical routes: conditions that maximize the simultaneous extraction of Pd and Pt, and conditions that favor selective Pd dissolution while minimizing Pt extraction. The results demonstrated that metal selectivity can be effectively controlled by adjusting operational parameters. Kinetic analysis further revealed differences in dissolution behavior between the two routes. The proposed aluminum-based salt system shows strong potential as a sustainable alternative for selective PGM recovery from complex secondary resources, supporting the development of recycling strategies for critical metals.

[1] F. N. Braga et al., Sep. Purif. Technol., 2025, 376, 134003.

This work was financially supported by national funds through FCT-Fundação para a Ciência e a Tecnologia, I.P., within the scope of the project PlatILPlus (2022.04478.PTDC, DOI:10.54499/2022.04478.PTDC). This work was further financially supported by: LSRE-LCM, UID/50020/2025; ALiCE, LA/P/0045/2020 (DOI: 10.54499/LA/P/0045/2020); and CICECO-Aveiro Institute of Materials, UID/50011/2025 (DOI:10.54499/UID/50011/2025) & LA/P/0006/2020 (DOI:10.54499/LA/P/0006/2020), financed by national funds through the FCT/MCTES (PIDDAC). N.S. acknowledges the European Union for the European Research Council for the starting grant DESignSX (Grant agreement ID: 101116461; DOI:10.3030/101116461). F.H.B.S. and F.N.B. acknowledge FCT for the researcher contract CEECIND/07209/2022 (10.54499/2022.07209.CEECIND/CP1720/CT0019) and the Ph.D. grant 2023.01749.BD (DOI:10.54499/2023.01749.BD), respectively.