Extraction and separation of platinum, palladium and rhodium using Cyanex 923 and their recovery from real samples

Platinum group metals find extensive use in automobile catalysts, space materials and cancer therapy. Their natural resources are limited thus their recovery from the secondary sector has assumed a great significance. Liquid–liquid extraction provides an effective methodology for the said purpose. The present paper discusses the extraction behavior of platinum(IV), rhodium(III) and palladium(II) from HCl, H2SO4 and HNO3 (0.10–6.0 mol L− 1) media by toluene solution of Cyanex 923. Detailed studies have been conducted by varying the equilibration time, temperature, diluent and concentration of extractant. An assessment of the loading capacity, regeneration power and stability of extractant has been made. The extraction behavior of associated metals namely gold, silver, iron, nickel, cobalt, chromium, copper and aluminum has been investigated and the conditions for the binary separations involving platinum metals have been optimized. The stoichiometric ratio of the extracting species for platinum and palladium has been worked out. Based on the extraction data platinum, palladium and rhodium have been recovered from some spent commercial materials.

► Cyanex 923 has been explored for the separation and recovery of Pt, Pd and Rh.
► Binary separations involving PGMs and associated metal ions are demonstrated.
► Proposed separation scheme validated using catalyst standard, NIST SRM-2556
► PGMs recovered from spent thermocouple wire, honeycomb, and palladium catalyst
► Simple strippants, H2SO4, HClO4, HCl and H2O with good efficiency are used.