Extraction studies of platinum group metals with cyanex 925 in toluene—role of tin(II) chloride in their separation

Abstract

Extraction of platinum group metals Os(VIII), Ru(IV), and Ir(III) was carried out from aqueous chloride media with Cyanex 925 in the absence and in the presence of tin(II) chloride. In the presence of hydrochloric acid (HCl) alone, only Os(VIII) and Ru(IV) get extracted quantitatively, while extraction of Ir(III) was incomplete. Further, Os(VIII) could be extracted at lower concentrations of HCl and Ru(III) at higher concentrations (3.5–5.0 M). In the presence of tin(II) chloride, the extraction of Ir(III) increases and becomes quantitative. However, it decreases to some extent in the case of Os(VIII) and Ru(IV). The extraction conditions for all the metal ions were optimized under influence of variables such as HCl concentration, reagent concentration, tin(II)chloride concentration, equilibration time, stripping agents, and effect of diverse ions. The separation of individual metal ions Os(VIII), Ru(IV), and Ir(III) was carried out by taking advantage of differences in their extraction and stripping conditions towards Cyanex 925. The methods developed were applied to the recovery of these metal ions from some real catalysts samples.