Three-way catalysts
Three-way catalysts used in exhaust-gas catalytic converters of automobiles contain platinum, palladium, rhodium, zirconium, and cerium. Oki et al. have developed a method which concentrates these metals by means of a two-step crushing procedure (Kim et al., 2010; Oki et al. 2010). The process makes it possible to increase concentration of rare-earth metals by a factor of five by first demolishing the honeycomb structure, and then peeling off the surface. To date, no process leading to recovery of individual rare-earth metals has been described.