The separation of rhodium and iridium by ion flotation

Mixtures of iridium(IV) and rhodium(III) as IrCl^2-₆ and RhCl^3-₆ are separated by ion flotation. The iridium(IV) is selectively floated from aqueous solutions of pH 2 and 0.05% Ce(IV) with either hexadecyltripropylammonium bromide (HTPAB) or hexadecyltributylammonium bromide (HTBAB). The rhodium(III) does not float under the same conditions. The floated iridium sublate is collected in n-butyl acetate without contamination by the unfloated rhodium. Data are presented also for the separation and recovery of the Ir(IV) and Rh(III) with the above surfactants, hexadecyltrimethyl-ammonium bromide (HTMAB) and hexadecyltriethylammonium bromide (HTEAB) from solutions of various sodium chloride and hydrochloric acid concentrations. The use of solvent sublation for recovering the floated iridium is examined. The separation is fast, practical, simple and does not require expensive reagents or apparatus. For these reasons, the separation of iridium and rhodium by ion flotation offers advantages over previous methods.