Selective Recovery of Precious Metals from Wastes by Photochemical Tandem Dissolution in Fe(III) Oxalate‐Halogen Systems

Green selective metallurgy of precious metals (PMs) from industrial multimetal wastes is attracting more attention. Herein, a tandem dissolution strategy of Fe(III) oxalate complex (FOC)-halogen (I/Br) sequential system was put forward. FOC-I system was crucial for selective recovery, which was suitable for Pt dissolution but passivation for Pd recovery, while FOC-Br system was universal for platinum group metals (PGMs) dissolution. Pt and Pd could be selectively and completely recovered from spent multi-PMs containing cordierite powder catalysts. 92.26% Pt and 94.73% Pd were selectively separated from spent unbroken monolithic cordierite catalysts. And 99.62% Au and 95.50% Pd could also be recovered from unbroken e-wastes, respectively. Oxygen radicals played a crucial role in the generation and migration of halogen reactive species such as I (Br)^•, I (Br)₂, and I (Br)₃ ^-. The method for the dissolution of halogen oxidation-coordination in FOC-I/FOC-Br systems was proposed. The recovered Pt/Pd-containing lixivium has been demonstrated to be a suitable precursor solution for the preparation of monolithic honeycomb catalysts used in air purification. The photochemical tandem dissolution in the sequential FOC-I/FOC-Br system will pave a way for the development of green metallurgy.