High-temperature cyanide leaching of platinum-group metals from automobile catalysts-laboratory tests. Rept. of Investigations/1991

The U.S. Bureau of Mines investigated leaching automobile catalysts with NaCN solutions at elevated temperatures to recover platinum group metals (PGM). The feed was virgin monolith rejects, used monolith, and used pellet catalysts. Leaching with a 5-pct NaCN solution for 1 h at 160 C dissolved over 97 pct of the PGM contained in the virgin monolith, over 85 pct of the PGM contained in the used monolith, and over 90 pct of the PGM contained in the used pellet catalyst. Over 99.8 pct of the dissolved PGM was recovered as a precipitate by heating the solution to 250 C for 1 h in an autoclave. The cyanide complexes were decomposed and free cyanide destroyed.