Extraction and separation studies on Pt(IV), Ir(III) and Rh(III) using sulphur containing extractant

• Cyanex 471X has been explored for the separation and recovery of Pt, Ir and Rh.
• Binary separations involving PGMs and associated metal ions are demonstrated.
• Proposed separation scheme applied to synthetic mixture and thermocouple wire.
• Simple strippants, H2SO4, thiourea and H2O with good stripping efficiency are used.
• Separations are achieved at room temperature without the use of any modifier.

The present work reports distribution of platinum(IV), iridium(III) and rhodium(III) from HCl, H2SO4 and HNO3 (0.1–6 mol L−1) media using Cyanex 471X diluted with toluene. Detailed studies have been conducted to evaluate the effect of different variables influencing the extraction such as 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 behaviour of associated metals namely gold, silver, iron, nickel, cobalt, chromium and copper has been investigated and the conditions for their binary separations involving platinum metals have been optimised. The stoichiometric composition of the extracting platinum and iridium species have been identified. Based on the extraction data separation schemes have been designed to recover platinum, iridium and rhodium from synthetic mixture and real sample.