A Group Separation Method for Ruthenium, Palladium, Rhenium, Osmium, Iridium, and Platinum Using Their Bromo Complexes and an Anion Exchange Resin

Abstract

A new group separation method for Re and PGE (Ru, Pd, Os, Ir, Pt) is described using a novel anion exchange chromatographic resin called TEVA. Re and PGEs are converted into bromo complexes by heating with HF-HBr mixture in a Teflon bomb at 518 K, by in situ-generated Br2 formed by reaction of HBr and HNO3. Distribution coefficients (Kd) of the bromo complexes onto TEVA resin in 0.1 M HBr with heating at 353 K for one night were 2,200, 16,000, 1,600, 5,500, 4,000, and 17,000 for Ru, Pd, Re, Os, Ir, and Pt, respectively, thus allowing 97% recovery of Re and PGEs in 5 mL of solution by 0.1 mL of resin. These strongly bound Re and PGE bromo complexes are stripped and recovered >90% by the following three steps: (i) addition of 6 M HCl at 353 K and 2.2 M HCl-5 M HBr at 353 K; (ii) heating the resin in 6 M HCl at 353 K to convert the bromo complexes into the chloro complexes with weaker affinities to the resin; and (iii) sequential addition of the HCl-HBr mixture at room temperature and 7 M HI. Neither the elution profile nor the recovery yield for a 0.2-g geological sample showed significant changes, indicating minimal matrix effects for the geological samples. Total blanks were < 14 pg for Ru, Pd, and Pt and < 10 pg for Re, Os, and Ir. This new technique, therefore, is suitable for simultaneous determination of subnanogram per gram of Ru, Pd, Re, Os, Ir, and Pt and Os isotope analysis in geological, mineralogical, and environmental samples without direct addition of toxic reagents required in distillation/extraction of Os or oxidizing of Ir.

Solid-phase extraction of iridium from soil and water samples by using activated carbon cloth prior to its spectrophotometric determination

“…The obtained result shows that the developed SPE method could be applied to the preconcentration of iridium from real samples such as water and soil samples without matrix interference. Solid-phase extraction Inductively coupled plasma-mass spectrometry 0.24 ng mL −1 Environmental and geological samples Dai et al (2000) Flow injection solid-phase extraction Flame atomic absorption spectrometry 0.11 μg mL −1 Synthetic mixture corresponding Di and Davey (1995) Solid-phase extraction UV-vis 20 μg L −1 Synthetic mixture corresponding Taher et al (1997) Solid-phase extraction ICP-MS -Geological samples Makishima et al (2001) Electroanalytical technique Stripping voltammetry 9.10 −7 mol L −1 -Svancara et al (2007) Solid-phase extraction UV-vis spectrophotometry 0.039 μg L −1 Water and soil samples This work…”

Solid‐phase extraction in the determination of gold, palladium, and platinum

“…New publications on Au and PGM ions are regularly appearing [82,89,[97][98][99][100][101][102]. Noble metals are most often sorbed as their chloride complexes and (rarer) as bromide complexes [97]. Most sorbents are selective to Au(III), Pd(II), and Pt(IV).…”

Precise Elemental and Isotopic Analyses in Silicate Samples Employing ICP-MS: Application of Hydrofluoric Acid Solution and Analytical Techniques

“…Makishima et al 19 decomposed 0.2 g of peridotite with HF-HBr in a Teflon bomb at 245 C, removed insoluble fluorides by centrifugation, and collected Ru, Pd, Os, Ir, Pt (PGEs) and Re from the supernatant with anion exchange chromatography. In this digestion, PGEs and Re are considered to be mixtures of fluoro-and bromo-complexes.…”

“…Makishima and Nakamura 19,30 developed a determination method of Ru, Pd, Os, Ir and Pt as well as 187 Os/ 188 Os isotope ratios in silicate samples using reductive digestion with HF-HBr in a Teflon bomb. However, it was found that highly refractory metal phases are not completely dissolved by the reductive digestion.…”