Simultaneous determination of palladium, platinum and rhodium in crude platinum samples by activation analysis and high-resolution gamma spectrometry

Instrumental neutron-activation analysis using a Ge(Li) detector has been investigated for the simultaneous determination of platinum, palladium and rhodium in crude platinum samples contained in lead cupels. This technique proved feasible and appears promising for extension to the determination of most of the noble metals.     

The rapid isolation and determination of iridium after simultaneous liquid-liquid extraction and determination of platinum,palladium, rhodium and gold

The proposed method provides a rapid isolation of iridium form the other noble metals, as well as from Ni, Cu, Fe, Cr, Co and Na. The scheme comprises an initial removal of ruthenium and osmium by volatilization of their tetroxides followed by the simultaneous extraction of platinum, palladium, rhodium and gold as their 2-mercaptobenzothiazole—tin(II) chloride complexes into chloroform. Iridium in the raffinate is complexed by the same reagent system, after boiling, and extracted into chloroform. The extracts after evaporation of the solvent are converted to hydrochloric acid solutions and the noble metals are determined by atomic absorption spectrometry. Satisfactory results are obtained for various noble metal solutions, and for a solid platiniferous sample.     

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.     

Acetothioacetanilide as a gravimetric reagent for palladium, platinum and rhodium

Acetothioacetanilide, CH(3)CO . CH(2) . CS . NH . C(6)H(5) is found to be a very suitable gravimetric reagent for Pd(II), Pt(II) and Rh(III). The complexes [composition, M(C(10)H(10)NOS)(2); for M = Pd(II) and Pt(II), and M(C(10)H(10)NOS)(3)] are stable and can be weighed after drying at 105-110 degrees . Separation from base metals has been studied, and a structural interpretation made from DTA, TG and infrared data.     

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.

---

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.

---

---

Research Fellow on leave from Banaras Hindu University, India.     

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.     

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.     

Neutron activation analysis of palladium,platinum and rhodium in lead foam

The determination of palladium, platinum and rhodium in industrial concentrates such as lead foam and raw lead by neutron activation analysis is described. The noble elements are separated from the matrix by spontaneous deposition on amalgamated copper powder prior to activation. After the determination of palladium and platinum, rhodium is coprecipitated on iron hydroxide, and the precipitate irradiated for the determination of rhodium. The results are compared with those obtained by fire assay. Research Associate of I.I.K.W., Belgium.     

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.     

Extraction and flame spectrophotometric determination of palladium and rhodium

Solvent extraction methods involving toluene, chloroform, 4-methyl-2-pentanone and pentyl acetate were studied for palladium and rhodium chelates. The palladiurn-salicylaldoxime chelate was extracted quantitatively into 4-methyl-2-pentanone at pH 3. The rhodium-diethyldithiocarbamate chelate was completely extracted into 4-methyl-2-pentanone at pH 8. The optimum combustion conditions for each of the organic extracts were then studied. The position of maximum emission intensity in the flame mantle was determined for each chelate and solvent system ; readings were taken at 363.5 mμ for palladium, and 369.2 mμ for rhodium. For palla-dium, when 4-methyl-2-pentanone was used instead of water as solvent, the emission intensity increased 21-fold. For rhodium, this kctone increased the sensitivity 27 times compared with water. A method is suggested for the separation and determination of palladium and rhodium in the same sample.     

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.     

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.     

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.     

Microwave-assisted aqua regia digestion for determining platinum,palladium, rhodium and lead in catalyst materials

This study investigated a microwave-assisted aqua regia digestion of catalyst samples prior to the determination of Pt, Pd, Rh and Pb by ICP-OES. While optimising the method, the effect of digestion temperature on the digestion efficiency was investigated. Few aqua regia digestions were also carried out using a high pressure asher, with a digestion temperature of 280 °C. In addition, XRD (X-ray diffractometry) was used to characterise digestion residue. The study showed that accurate and reliable results for Pt, Pd, Rh and Pb in a recycled monolith catalyst (NIST SRM 2557) were obtained by ICP-OES after the microwave assisted aqua regia digestion. The amounts of Pt, Pd and Rh in the prepared catalyst samples were also at the expected levels. Furthermore, the results indicated that the main part of the impurities and supporting material elements can be quantitatively extracted from the catalyst samples by using the microwave-assisted aqua regia sample pre-treatment.     

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.     

Determination of palladium, platinum and rhodium in geologic materials by fire assay and emission spectrography

A method is described for the determination of palladium down to 4ppb (parts per billion, 10(9)), platinum down to 10 ppb and rhodium down to 5 ppb in 15 g of sample. Fire-assay techniques are used to preconcentrate the platinum metals into a gold bead, then the bead is dissolved in aqua regia and diluted to volume with 1M hydrochloric acid. The solution is analysed by optical emission spectrography of the residue from 200 mul of it evaporated on a pair of flat-top graphite electrodes. This method requires much less sample handling than most published methods for these elements. Data are presented for G-1, W-1, and six new standard rocks of the U.S. Geological Survey. The values for palladium in W-1 are in reasonable agreement with previously published data.     

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.