The separation of platinum and iridium by ion flotation

The anionic chlorocomplexes of platinum(IV) and iridium(III) are separated by ion flotation from acidic, aqueous solutions with cationic surfactants of the type C₁₆H₃₃NR'₃Br, where R' is methyl, ethyl, n-propyl, or n-butyl. The PtCl₆^2-, which forms readily floatable salts with each of the surfactants, is selectively floated from the IrCl₆^3- and recovered after flotation in n-butyl acetate. The efficiency of the separation increases as the R' chain length increases and a quantitative separation is obtained with hexadecyltributyl-ammonium bromide (HTBAB) in 0.1 M HCl solutions. Since the flotation properties of Ir(IV) are similar to those of Pt(IV), hydroxylamine hydrochloride is used to reduce Ir(IV) to Ir(in) selectively in the presence of Pt(IV).