Wet recovery technology of platinum group metals

Wet recycling of PGMs refers to the use of chemical reagents to dissolve waste containing PGMs, convert PGMs into complex ion forms, and then complete the enrichment and purification of PGMs through ion exchange, extraction, precipitation, filtration and other processes; it is mainly divided into cyanidation method, hydrochloric acid + oxidant and other process forms.

1. Cyanidation method: Cyanidation method was originally used for the extraction of Au and Ag, and later for the extraction of PGMs. In alkaline solution, cyanide uses O2 in the air to selectively dissolve PGMs and does not react with the carrier, so that PGMs are separated from the carrier; then Zn and Al are used to replace PGMs. The mechanism of cyanide dissolving PGMs is: CN- ions are adsorbed on the surface of PGMs metal, PGMs atoms and lone pairs of electrons provided by C form δ bonds, and PGMs cyanide complexes exist relatively stably.
2. Hydrochloric acid + oxidant: Add one or more oxidants (such as HNO3, NaClO, NaClO3, HClO, Cl2, H2O2) to the hydrochloric acid system to oxidize PGMs to ionic state and then form chloride ion complexes to dissolve, so as to achieve the purpose of PGMs leaching and separation of PGMs from carriers.