High-selective platinum and palladium capture using polyamide 6: A potent material for platinum group metals’ recovery from spent car catalytic converter

Platinum (Pt) and palladium (Pd) are commonly integrated into automotive catalytic converters to convert harmful emissions into relatively safer substances. Their scarcity has resulted in the rapid development of an industry focused on their recovery. Polyamide 6 (PA6), a microplastic pollutant, is a common industrial material. Proper recycling of PA6 can mitigate the environmental impact caused by its microplastic pollution. This work revealed the capability of PA6 in recovering Pt and Pd from solution. Experimental data demonstrated that PA6 recovered about 90% of Pt and 70% of Pd. Importantly, PA6, without any functionalization or modification, adsorbed Pt and Pd without adsorbing present competing metals, exhibiting notably greater recovery selectivity towards Pt and Pd than materials discussed in other works. Furthermore, approximately 81% of Pt and 83% of Pd could be desorbed from PA6 as noted by the desorption studies. After obtaining fitted results using empirical equations and surface group identification, chelation and electrostatic interaction were discerned to be the key pathways for Pt and Pd recovery. This study represents a novel investigation into PA6's adsorption selectivity for Pt and Pd, through which experimental results confirm PA6's potential as a practical, environmentally-friendly alternative for Pt and Pd recovery, distinguishing it from its conventional counterparts.