Circular Recovery of Platinum Group Metals Using Wool-Derived Keratin

Platinum group metals (PGMs) are critical raw materials widely used in industrial applications due to their unique physicochemical properties. However, their scarcity, high economic value, and the environmental impact associated with conventional mining have intensified the search for sustainable recovery strategies. Secondary sources, particularly spent automotive catalytic converters, represent an attractive alternative for PGM recovery. In this context, bio-based adsorbents have emerged as promising materials for environmentally friendly metal separation processes. Keratin, a naturally occurring biopolymer derived from wool, contains functional groups such as thiol, amino, carboxyl, and disulfide ligands that can promote selective metal binding [1].

This work investigates the use of wool-derived keratin as a sustainable adsorbent for the recovery of PGMs from synthetic solutions. Adsorption kinetics and thermodynamic studies were performed to characterize the adsorption process, while morphological and structural analyses were conducted to elucidate adsorption mechanisms and metal–keratin interactions.

The results demonstrated the selective affinity of keratin for PGMs in acidic media, with palladium exhibiting the highest adsorption capacity among the PGMs. Chemical pre-treatment significantly influenced adsorption performance, highlighting the importance of keratin functional groups in metal coordination. These findings demonstrate the potential of wool-derived keratin as a low-cost and sustainable material for selective PGM recovery from secondary resources.

[1] A.N. Nohabar, F.H.B. Braga, F. Sosa, N.A.P. Coutinho, J. Passos, Waste Manag. 212 (2026) 115346

This work was supported by 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 FCT, I.P. /MCTES through national funds: LSRE-LCM, UID/50020/2025 (DOI: 10.54499/UID/50020/2025); 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), LA/P/0006/2020 (DOI: 10.54499/LA/P/0006/2020). R. Carvalho acknowledges FCT for the Ph.D. grant 2025.06718.BDANA.