A solvent-extraction scheme for the determination of platinum,palladium, rhodium,iridium and gold in platiniferous materials

The integrated scheme described for the determination of five noble metals, combines solvent extraction procedures with atomic absorption spectrometric finishes. It comprises an initial extraction of gold, a simultaneous extraction of platinum and palladium as iodides, and a subsequent simultaneous extraction and preconcentration of rhodium and indium as their 2-mercaptobenzothiazol? complexes. The same solvent, methyl isobutyl ketone, and the same acidity, 6 M, are used throughout the extractions. As large amounts of platinum and palladium can be extracted quantitatively as readily as small amounts, the proposed scheme is applicable to a wide range of platiniferous materials, particularly to those with extremely high Pt + Pd to Rh + Ir ratios.     

Recovery of platinum,palladium, rhodium,iridium, and gold after lead fusion and perchloric acid parting

A method is described for the wet analysis of the lead-noble metals button which is parted with perchloric acid after heating at 160–180°C, thus resulting in the complete dissolution of platinum, palladium, rhodium, and gold, indium remains totally unattacked. Quantitative group precipitation of the precious metals from the diluted lead perchlorate filtrate solution is possible with 2-mercaptobenzothiazole as precipitant. The noble metals precipitated are isolated by filtration and are easily determined. The proposed procedure is rapid, precise, and applicable to a wide variety of platiniferous materials.     

The express simultaneous neutron activation determination of gold,palladium and platinum

The method of express neutron-activation (NA) determination of Au, Pd and Pt has been developed. The method is based on the quantitative isolation of¹⁹⁸Au+¹⁹⁹Au and¹⁰⁹Pd activities by extraction with organic sulfides. The radiation of¹⁰⁹Pd is measured on a thin NaI(Tl) crystal and that of¹⁹⁸Au and¹⁹⁹Au on a Ge(Li) detector. The calculations of interferences from gold have been performed for various neutron fluxes and various cadmium ratios. Some interferences introduced by other competitive nuclear reactions into the determination of Pt by its daughter isotope¹⁹⁹Au are discussed.     

A new solvent extraction scheme for the separation of platinum,palladium, rhodium and iridium

A new scheme is proposed for the separation of platinum, palladium, rhodium and iridium in hydrochloric acid solutions, by solvent extraction. Platinum and palladium are complexed with 2-mercaptobenzothiazole and potassium iodide and simultaneously extracted into chloroform, thus separating them from rhodium and iridium. Palladium is separated from platinum by extracting its dimethylglyoxime complex into chloroform, while rhodium is separated from iridium by extracting its 2-mercaptobenzothiazole complex into chloroform after reduction with tin(II) chloride.     

Extractive spectrophotometric determination of platinum, rhodium and iridium

Platinum, iridium and rhodium in mixtures are determined sequentially, with rubeanic acid, tin(II) chloride and tin(II) iodide respectively. The working ranges (in microg) are: Pt 7-100, Rh 7-70, Ir 7-30.     

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

A simple classification of various sorbents and solid-phase extraction procedures used for preconcentration of trace levels of Au, Pd, and Pt from different sample types is proposed in this review article. The large variety of available sorbents/procedures has been organized according to expected mechanisms of sorption process (complex formation; ion exchange; adsorption; ion-imprinted or molecularly imprinted polymers); according to the kind of monomeric units of the polymer matrix as well as on the basis of the kind of functional group responsible for main performance characteristics (selectivity, capacity) of the sorbent. Advantages of chemically modified sorbents, sulfur-containing sorbent extractants, and ion-imprinted polymers, together with rational pretreatment by means of microwave treatments, scaling down of enrichment, and quantification by means of flow and flow injection approaches are given. Preferred instrumental techniques for quantification of ppb levels of Au, Pd, and Pt in prepared concentrates/column eluates are multielement instrumental techniques: inductively coupled plasma optical emission spectrometry (ICP-OES), and inductively coupled plasma mass spectrometry (ICPMS). Excellent limits of detection at picogram levels of these analytes are provided by electrothermal atomic absorption spectrometry (ETAAS), generally in single-element mode and the neutron activation analysis (NAA), while X-ray fluorescence spectrometry and flame AAS are rarely applied because of lack of sensitivity at sub-ppm levels of Au, Pd, and Pt. Some problems of atomic spectrometric quantification techniques and their representative limits of detection are given. Recent applications to geological, industrial, pharmaceutical, biological, and other materials are tabulated. References have been selected mostly from the period 1995 to 2010.     

The determination of platinum,palladium, rhodium,and iridium in perchloric acid solutions of associated base metals

Summary The report deals with an unsuccessful attempt to corroborate the reported successful conversion of platinum and base metals in a perchloric acid medium to the chloride salts. A hydrolytic precipitation and subsequent dissolution in hydrochloric acid removed the perchlorate ion with sufficient efficiency to allow the use of a cation exchange separation. A subsequent series of extractions and spectrophotometric methods was used to determine the platinum metals.

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Zusammenfassung Der Versuch, Platin und unedle Metalle in Perchlorsäure-Medium in Chloride zu überführen, verlief erfolglos. Die hydrolytische Fällung und nachfolgende Lösung in Salzsäure führte zu hinreichender Entfernung der Perchlorationen, um eine Trennung mit einem Kationenaustauscher vorzunehmen. Extraktionen und spektrophotometrische Methoden wurden zur Bestimmung der Platinmetalle verwendet.

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Research Fellow on leave from Banaras Hindu University, India.     

Particle size determination of platinum, palladium and rhodium

Simple and sufficiently accurate equations are suggested for calculating the particle size of most frequently used supported or unsupported platinum metal catalysts from the amount of chemisorbed gas.

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Graphite furnace atomic absorption spectrometric determination of iridium,rhodium and ruthenium in high-purity platinum after matrix extraction

Ir, Rh and Ru are separated from a large excess of platinum by extraction with isoamyl alcohol-isobutyl methyl ketone mixture. Graphite furnace atomic absorption spectrometry using the method of standard addition is then used to determine the metals with satisfactory precision and accuracy.     

Electrothermal atomization-laser induced fluorescence determination of iridium,rhodium, palladium,platinum and gold at the ng/l level in pure water

Trace determination of Au, Rh, Ir, Pd and Pt in pure water solution has been performed by electrothermal atomization-laser induced fluorescence (ETA-LIF). Limits of detection obtained are in the ng/l⁻¹ range, improving previously published absolute limits of detection by one or two orders of magnitude. The day to day reproducibility for iridium is around 8%. Thus, the ETA-LIF technique can be used routinely for the determination of precious metals at ultratrace concentrations.     

Simultaneous neutron activation determination of palladium,gold, platinum and iridium in some natural materials

A method for rapid simultaneous neutron activation determination of Pd, Au, Pt and Ir in USGS standard rocks, ores and minerals has been developed based on selective extraction of determined elements. Results of determination of noble metals in standard rocks are discussed.     

The simultaneous determination of osmium,ruthenium, iridium and gold in platinum by neutron activation analysis

Osmium, ruthenium, iridiuim and gold can be determined simultaneously in 100-mg platinum samples after irradiation for 11 days at a thermal neutron flux of 4'1011 n.cm^-2.sec^-1. An addition method of analysis is used; samples are dissolved in small sealed silica tubes before activation. After irradiation, Os and Ru are distilled from sulfuric acid-sodium bromate, Ru being determined by counting the 498-keV peak of ¹⁰³Ru; Os is determined after a second distillation. Gold is extracted with ethyl acetate from the residue of the first distillation; the ratio ¹⁹⁸Au/¹⁹⁹Au is a direct measure for the gold content, with appropriate correction for the second-order reaction ¹⁹⁶Pt(n,γ)¹⁹⁷Pt→¹⁹⁷Au(n,γ)¹⁹⁸Au. Ir is determined in the residual aqueous phase using the 317-keV peak of ¹⁹²Ir; a correction for the platinum activity (¹⁹¹Pt) is made. The lower limit of determination is ca. 0.5 p.p.m. for ruthenium, ca. 0.2 p.p.m. for osmium, ca. O.1 p.p.m. for gold and ca. O.1 p.p.m. for iridium. After a separation of Pt from Ir, the sensitivity for Ir can easily be improved to < 10 p.p.b.     

Heteronuclear rhodium, palladium, platinum, and gold organoimido complexes from dinuclear organoamido rhodium precursors

Treatment of the organoamido complexes [Rh(2)(mu-4-HNC(6)H(4)Me)(2)(L(2))(2)] (L(2) = 1,5-cyclooctadiene (cod), L = CO) with nBuLi gave solutions of the organoimido species [Li(2)Rh(2)(mu-4-NC(6)H(4)Me)(2)(L(2))(2)]. Further reaction of [Li(2)Rh(2)(mu-4-NC(6)H(4)Me)(2)(cod)(2)] with [Rh(2)(mu-Cl)(2)(cod)(2)] afforded the neutral tetranuclear complex [Rh(4)(mu-4-NC(6)H(4)Me)(2)(cod)(4)] (2), which rationalizes the direct syntheses of 2 from [Rh(2)(mu-Cl)(2)(cod)(2)] and Li(2)NC(6)H(4)Me. Reactions of [Li(2)Rh(2)(mu-4-NC(6)H(4)Me)(2)(CO)(4)] with chloro complexes such as [Rh(2)(mu-Cl)(2)(CO)(4)], [MCl(2)(cod)] (M = Pd, Pt), and [Ru(2)(mu-Cl)(2)Cl(2)(p-cymene)(2)] afforded the homo- and heterotrinuclear complexes PPN[Rh(3)(mu-4-NC(6)H(4)Me)(2)(CO)(6)] (5; PPN=bis(triphenylphosphine)iminium), [(CO)(4)Rh(2)(mu-4-NC(6)H(4)Me)(2)M(cod)] (M = Pd (6), Pt(7)) and [(CO)(4)Rh(2)(mu-4-NC(6)H(4)Me)(2)Ru(p-cymene)] (8), while the reaction with [AuCl(PPh(3))] gave the tetranuclear compound [(CO)(4)Rh(2)(mu--4-NC(6)H(4)Me)(2)[Au(PPh(3))](2)] (9). The structures of complexes 6, 8, and 9 were determined by X-ray diffraction studies. The anion of 5 reacts with [AuCl(PPh(3))] to give the butterfly cluster [[Rh(3)(mu-4-NC(6)H(4)Me)(2)(CO)(6)]Au(PPh(3))] (10), in which the Au atom is bonded to two rhodium atoms. Reaction of the anion of 5 with [Rh(cod)(NCMe)(2)](BF(4)) gave the tetranuclear complex [Rh(4)(mu-4-NC(6)H(4)Me)(2)(CO)(6)(cod)] (11) in which the Rh(cod) fragment is pi-bonded to one of the arene rings, while the reaction of the anion of 5 with [PdCl(2)(cod)] afforded the heterotrinuclear complex 6 through a metal exchange process.     

Simple and rapid flow-injection spectrophotometric determination of carbaryl after liquid-liquid extraction

A simple procedure was developed for the spectrophotometric determination of carbaryl and its hydrolysis product 1-naphthol in water. These compounds are extracted into xylene and back-extracted, as the 1-naphtholate, with 0.2 M NaOH. A 600-μl volume of the alkaline extract is injected into a flow analysis manifold which provides the reaction between naphtholate and 50 μg ml⁻¹ p-aminophenol solution in the presence of 0.004 M KIO₄ and spectrophotometric measurement is carried out at 596 nm. The method provides a limit of detection of 26.5 ng ml⁻¹ carbaryl and a sample frequency of 110 injections per hour. Recoveries in different types of matrices vary from 95 to 102%.     

Electrochemical absorption and oxidation of hydrogen on palladium alloys with platinum, gold and rhodium

Thin layers of Pd and its alloys with Pt, Au and Rh were prepared by electrodeposition on a Au substrate. Hydrogen electrosorption by the obtained electrodes was studied in 0.5 M H(2)SO(4) solution using cyclic voltammetry and chronoamperometry. The influence of the alloying process on selected thermodynamic (the amount of absorbed hydrogen, the stability of the β-phase, the extent of the absorption/desorption hysteresis) and kinetic aspects (the rate of hydrogen absorption and absorbed hydrogen oxidation) of hydrogen absorption and desorption was examined. It was found that the addition of the non-absorbing elements to Pd results in faster kinetics of the hydrogen electrosorption process and a smaller absorption/desorption hysteresis.     

FIA-FAAS system including on-line solid phase extraction for the determination of palladium, platinum and rhodium in alloys and ores

A number of aliphatic mono- and triamines have been investigated as potential reagents for solid phase extraction of Rh, Pd and Pt. Platinum group metals are recovered from hydrochloric acid solutions as ionic associates of their chloride complexes with protonated amines. The recovery of metals depends both on hydrophobic properties of amine and sorbent and on sorption behaviour of amine itself. For on-line solid phase extraction of platinum group metals 4-(n-octyl)diethylenetriamine and hyper cross-linked polystyrene sorbent SSPS have been applied. Quantitative recovery of rhodium and platinum in the form of their hexachloride complexes was achieved under non-equilibrium conditions of on-line dilution. Metals recovered are quantitatively eluted with 1 M hydrochloric acid solution in ethanol. A new FIA-FAAS method for the determination of Rh, Pd and Pt in solutions based on the decomposition of ores and alloys has been proposed. The RSD values are 0.03-0.08 at 50-ppb concentration level. The detection limits are 3-8 ppb for 1 min of preconcentration. The accuracy of the procedure was verified by the analysis of standard reference materials of sulfide ores and alloys.     

Studies on iridium and platinum determination in metallic rhodium by NAA and CPAA

The determination of Ir and Pt in rhodium neutron monitors was investigated via¹⁹²Ir and¹⁹⁹Au after neutron activation, via¹⁹¹Pt and¹⁹⁴Au–¹⁹⁶Au after proton activation. Ir was determined by instrumental NAA. A chemical separation of gold, with a yield measurement method by a radioactive tracer, was developed for platinum determination after neutron or proton irradiation.